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WORLD METEOROLOGICAL ORGANIZATIONOperational HydrologyReport No.2AUTOMATIC COLLECTIONAND TRANSMISSION OFHYDROLOGICAL OBSERVATIONSprepared hythe Working Group on Instruments and Methods ofObservation of the Commission for HydrologyI WMO - No. 337 IIMO-WMOCENTENARYSecretariat of the World Meteorological Organization • Geneva • Switzerland1973

© 1973, World Meteorological OrganizationNOTEThe designations employed and the presentation of the material in this publication do notimply the expression of any opinion whatsoever on the part of the Secretariat of the WorldMeteorological Organization concerning the legal statns of RUy country or territory or of itsauthorities, or concerning the delimitation of its frontier.s.

CONTENTSFOREWORDSUMMARY..................................................................(English, French, Russian, Spanish)•.......................•.....VVIICHAPTER 1 AUTOMATION OF HYDROLOGICAL OBSERVING STATIONS•••••••••••••••••••..•............•..•....•...........•• 0·•••••••••Reasons for introducing automation••••••••.••••..••.•••.•••..•....Adequacy af present data collection programme •••••••••••••••••••••Manual versus automatic.........................................•.Factors affecting choice of instruments and type of installationfor automatic hydrological observing stations••••.•.•..•....•.••••Local conditions.•......•........•................•...............Sources of power........•.•.......................................Accuracy requirements•..•.•.......................................Proposed life of station.............•..•...................•••...Maintenance....•..•..................................•...•..••....Transmission requirements.•.......................................Treatment of data..........•......................................Selection of instruments............•.............•...............Network design .Aids for selection of instruments .Questionnaire on instruments of proven reliability .Special considerations .12224577889101010101111CHAPTER 2 TRANSMISSION OF HYDROLOGICAL OBSERVATIONS•..••.......•..••..•• .Systems of data transmission .General considerations in selection of systems .Transmission links.........•......................................Dedicated land lines .Commercial telephone lines .131316171718

IVAUTOMATIC HYDROLOGICAL OBSERVATIONS2. telegraph lines..•....•......•.....•................ 10Direct radio links - .Satellite links. IO" .Receiving system••.•.•....•.................•.... 0· ••••••••••••••••••18191919CHAPTER 3 EXAMPLES OF AUTOMATIC TRANSMISSION SYSTEMS FOR HYDROLOGICALPURPOSES. •• • ••• . •• •• •• •• • . . • •. • . •• ••• • . • •. • •. • . •• •. • •••• •••• •• I (Canada).•.....................•................•..•.... 21Example II (U.S.A.). The Hy-Tel remote rodio telemetry system ••• 26Example III (U.S.S.R.). Automatic hydrological recording station(AHRS) . 30Example IV (U.S.S.R.). Mudflow radio warner (MRW) ••••••••.•••••• 32Example V (France). Tele-snow-gauge with moving horizonto1 beam. 36Example VI (Hungary).Hydra II automatic digital telemeterings·ystem •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 41BIBLIOGRAPHY. . . • • . . •• . • •. • •• . . •• ••• • ••• •• . • . . • . • • ••• . . • . . ••• •••• • . ••• . •. • . . 45ANNEX 1 Questionnaire on hydrometeorological instruments of provenreliability. • • • • . . . . . . • . • • • . • • • • • . ... . . . . . . . . . • • . • • • . . . . . . . . . . • 47ANNEX 2 List of instruments of proven reliability and instruments forautomation of hydrological observations••••••••••.•..•.•...••• 49

FOR E W0 R DAt its third sessioIT the WMO Commission for Hydrology (CHy) established aWorking Group on Instruments ond Methods of Observation. One of the tasks of theGroup was to complete a report on automatic equipment for observing and transmittinghydrological elements•. The G~oup consisted of Messrs. E. Walser (Switzerland)(Chairman), M~ Hendler (Canada), M. F. E. Hinzpeter (Federal Republic ofGermany), E. L. Peck (U.S.A.), K. D. Zavjalov (U.S.S.R.) and H. Schtlfer (IAHS).Dr. K. D. Zavjalov was later replaced by Mr. N. Ja Solov'ev (U.S.S.R.). The reportwas accordingly prepared and is reproduced in this present publication entitledIIAutomatic collection and transmission of hydrological observations".It is believed that it will be of particular value to national services andin particular to experts who have to install automatic stations and to select for thispurpose the most useful instrumental equipment.The terms of reference of the CHy Rapporteur on Instruments, Dr. E. L. Peck,required him to collect recommendations from Members on hydrometeorological instrumentswhich they have found reliable in specified environments, and to consolidatethese recommendations in a report for the use of Members and others in establishingnetworks. The group therefore maintained close collaboration with him especially incollecting information from Members. Analysis of the information he collectedrevealed that most of it could with advantage be included in the present. report,which is, therefore, the result of the common efforts of the Working Group and of theRapporteur on Instruments.Taking into account the rapid developments in the field of equipment foroperational hydrology, the report corefully combines the new advanced data collectionand transmission systems with the present conventional approaches, thus increasing itsapplicobility to different stages of development ond modernization in differentcountries. The report is a timely contribution which provides 0 useful link betweensimple, classical instrumentation and the complex modern installations for transmittingdata by satellites.I am pleased to have this opportunity of expressing to Mr. Walser and theother members of the Working Group, and to Dr. Peck, the sincere appreciation of theWorld Meteorological Organization for the time and effort they have devoted to thepreparation of this publication.~.. .D. A. DaviesSecretary-General

SUM MAR YMost hydrological observation networks and collection systems have developedin response to particular, localized problems or scientific interests without takinginto account future requirements. For various reasons the quality, quantity andtimely availability of hydrological dato are inadequate for present development needsin general, and in particular, for the timely preparation and issuing of hydrologicalforecasts and warnings.Taking into account the present needs, this report discusses the advantagesand disadvantages of updating, modernizing and automating the data collection systemsin the light of the recent technological progress in automatic instrumentation andtransmission systems for hydrological purposes. Detailed guidance is included concerningthe choice of automatic instruments and types of installation for variousclimatic and geographical conditions.A description of basic systems of transmission of hydrological abservationsond guidance for their selection are followed by examples of operational automatictransmission systems for hydrological purposes in various countries. Technical informationon instruments of proven reliability is tabulated in a systematic and convenientform in an annex.

RES U M ELa plupart des reseaux d'observation hydrologiques et des systames de rassemblementdes donnees obtenues grace a cas reseaux ant ete mis au point pour resoudredes problemes particuliers, d'interet local, au pour repondre a des besoinsscientifiques tsans qulil soit tenu compte des necessites futures. Pour diversesraisons, les donnees hydrologiques one sant pas d'ossez bonne qualite, pas ossez nombreuseset pos disponibles assez tot pour l'ensemble des besoins de developpementactuels at, en particulier, pour qulil soit possible de preparer at de diffuser atemps des previsions et des avis hydralogiques.En56 fondant sur les necessites actuelles, Ie present rapport expose lesQvantages at les inconvenients qulil y aurait a mattre a jour, moderniser at Qutomatiserles systemes de rassemblement des donnees, compte tenu des perfectionnementstechniques apportes recemment aux instruments et aux systemes de transmission automatiquesutilises a des fins hydrologiques. Le rapport contient des indicationsdetaillees sur le choix d'instruments et de types d'installations automatiques adaptesa diverses conditions climatiques et geographiques.Une description des systemes fondamentaux de transmission d'observationshydrologiques et quelques directives concernant Ie choix de ces derniers sont suiviesd'exemples de systemes operationnels de transmission automatique utilises a des finshydrologiques dans divers pays. Le lecteur trouvera en annexe un tableau OU sontpresentes de fa~on systematique et commode des renseignements techniques sur lesinstruments dont la fiabilite est etablie.

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RES U MENLa mayoria de las redes hidro16gicas de observaci6n y la mayor parte de lossistemas de concentraci6n de datos se han creado para so!ucionar problemas especificosy localizados 0 para responder a intereses cientIficos, pera sin tener en cuento lasnecesidades futures. Por diverses rezones, 10 calidad, cantidad y oportuna disponibilidadde los datos hidro16gicos no son adecuadas para satisfacer las actuales necesicladesen general ni, en particular, para pader preparar y publicar a su debido tiempopredicciones y avisos hidro16gicos.Teniendo en cuenta las actuales exigencies, en este informe se examinen lasventajos y desventajas que presenta 10 actualizaci6n, modernizaci6n y automatizacionde los sistemas de concentracion de datos, fund6ndose en 10$ recientes progresos tecno16gicosen materia de instrumentos automaticos y sistemas de transmisi6n para fineshidro16gicos. Igualmente, se facilitan directrices detalladas para la selecci6n delos instrumentos automaticos y de los tipos de instalaci6n correspondientes a diver­50S condiciones climaticos y geograficasoA 10 descripci6n de los sistemas b6sicos de transmisi6n de observacioneshidro16gicas y a las directrices para su selecci6n se ocompanan ejemplas de sistemasde transmisi6n automaticos y operativos para fines hidro16gicos en diversos paIses.En un onexo se facilita informacion tecnica sabre instrumentos de reconocida fiabilidad,presentada en forma tabular, sistem6tica y adecuada.

C HAP T E K 1AUTOMATION OFHYDROLOGICAL OBSERVING STATIONS1.1 IntroductionHydrologicol observing statians measure the primary elements of the hydrologicalcycle. There is an interrelationship between the primary elements andother, predominantly meteorological, parameters. For this reason, hydrologicalobserving stations ore normally equipped with auxiliary facilities for measuringthese parameters.Automatic observing systems are now in widespread use in different fieldsof geophysics. New generations of these systems are capable of operatinq for moreand more extended periods of time unattended. Highly sophisticated automaticstations have been developed, to correspond to modern demands for transmission includingsatellite interrogation and data processing.There is a need for classification of automatic hydrological observingsystems into a meaningful framework defined in the light of the overall functions ofsystems or stations. Such a classification should be simple because of the complexcharacter of outomatic hydrological systems. When defining a classification,descriptive terms such as "fully-" or IIsem i-automotic systems" should not be osedbecause they are too qualitative.FQr the purpose of this report, the following three categories of hydrologicalobserving stations are defined:Automatic hydrological observing stationA hydrological station at which instruments make and record theobservations automatically.Telemetering hydrological observing stationA hydrological station at which instruments make, but do not record,the observations automatically, and transmit them automatically tothe receiving centre.Telemetering automatic hydrological observing stationA hydrological station at which instruments make and record theobservations automatically and transmit them automatically to thereceiving centre.

2AUTOMATIC HYDROLOGICAL OBSERVATIONS1.2Reasons for introducing automation1.2.1The primary reason for changing to, or increasing the degree of, Qutomationin a data callection network is the need to improve the quality, quantity and/ortimely receipt of the data. Most present day hydrological networks were developedin response to particular, localized problems or scientific interests and not with aspecific objective of satisfying the future requirements for all hydrological purposes.Many networks depend on manual, in-situ observations by observers. This isa slow and laborious way of collecting data. Consequently, there is often inadequatespatial information for those areas where observers are not readily available. Datafrom such networks are sufficient for simple general hydrological resource studies,but are of only limited value for project planning and operation. In most cases thedata collection programme does not meet the requirements for timely preparation andissuing of·hydrolagical forecasts and warnings or for synoptic monitoring.As the demands for hydrological planning and forecasting services increase,the agency or agencies responsible for providing such services will be faced with adecision on the need for modernizing the data collection network.1.2.2 Manual versus automaticIt is often frustrating to maintain a network of stations manned by observerswhen there may be a serious need to change to an automoted system. Changingobservers to improve the quality and/or reliability of reporting is a continualproblem. Although the trend for people to be more mobile has resulted in more frequentchanges in observers than has been possible in the' past, it is becomingincreasingly difficult to obtain observers who are willing to make measurements onweekends. Moreover, there is a steady rise in the cost of observers, their recruitmentand training and the processing of data collected from hydrological networksmanned by observers.Although such factors may make a change to a more· fully automated systemappear attractive lthere are problems and costs associated with automated systemsthat should be carefully evaluated before a final decision is taken. A cost/benefitapproach should be the primary basis for such a decision. It is, however, extremelydifficult to determine the actual value of either the old or new system or even thecomparative figures. This is especially true when the data are utilized for severalpurposes and costs must be allocated accordingly. In addition to cost comparisons,the following questions should be given careful consideration.(a)(b)(c)Is there a real need to improve the quality of the data?Is there a real need to increase the quantity of data(i.e. improve the areal coverage)?Is there a real need to reduce the time required forreceipt of data?

AUTOMATION OF OBSERVING STATIONS3In considering the above questions it should be recognized thot the problem is adynamic one. Rapid chonges in the field of hydrology, instrumentation and means oftransmission of data as well as in the demand for services make it imperative thatanticipated future conditions be given proper evaluation.The automation of data collection systems may reduce or eliminate most humanobservational errors. However, this advontage moy be offset by the introduction ofinaccuracies caused by instability in the sensing, recording or transmission system.Errors resulting from such instability in electronic systems may be much moredifficult to identify and correct than the human ones and quolity control of dot~then becomes highly dependent upon the quolity of maintenance.A distinct advantage in most automated systems is the continuous recordingcompared to the point measurements obtained by manual observations. For example,continuous flow hydrographs, required for mony hydrologicol analyses, permit thedetermination of maximum and minimum values, which are essential for the developmentand application of mathematical and physical hydrological models that are now incommon use.The quality of the data may be improved by data collection techniques otherthan the automation of the present system. Remote sensing technology moy providemeans to obtain acceptable areal averages for certain elements. Many such improvedtechniques ore now being developed ond these should be evoluated for the present andfuture requirements before automation of a point measurement network is undertaken.One of the most obvious advantages of automation is the obility to obtoindata for locations where observers are not available. However, this should not be abasis for a decision· to automate the entire network. From a cost consideration themost valuable data collection programme may be one in which automation is used foronly a portion of the area or for only those areas for which data are required on a"real time" basis.The rapid advancement that is taking place in the fields of instrumentationand data transmission may provide ways and means for improved collection of data inthe near future that would be of great use, at less overall cost than those atpresent in use. Information on considerations that should be given to selection ofa transmission sy~tem is given in Chapter 2.Careful consideration should be given to the possible advantages to begoined by automating only that portion of the . system required for present andforeseeable needs. However, the initial plans for any automatic system shouldinclude provisions for expansion and for the incorporation of neW technology wheneverpossible. Since the demands for improved data, quality and quantity, normallyincrease with time, a constant effort must be devoted to improve instrumentation.

4 AUTOMATIC HYDROLOGICAL OBSERVATIONSA description of the various possible procedures as well as different equipmentused in the handling and processing of' hydrological data is given in WHOTechnical Note No.115, Machine processing of hydrometeorological data. Any decisionregarding the eventual treatment of recorded observations will have a very importanteffect an the type of instruments to be used to obtain the data.The use of the computer is most, profitable when handling either_ largequantities or very complicated series of observations. It is usually not justifiableto consider this means of handling the data from a small number of stations. Inthese cases, a relatively small staff can handle the treatment of data with 0 minimumof expense. On the other hand, if expansion of the observation network is envisagedin the near future, it wauld probably be reasonable to immediately start developinga system for automatic processing based on the information collected from the initialsmall number of stations.It should be noted that any existing network, either for hydrological observationsor for other parameters, will have an impact on any decision. If, in the operationof the hydrological network, much money has been invested in the past to installanalogue recorders, it could be more economical not to convert to digital recorders,but to continue using the analogue apparatus and available equipment to convert the analoguerecording to machine input form such as cards and magnetic tapes. Some hydrologistsprefer this latter procedure of having as a basic record an analogue recordingbecause they feel that this type of record permits the person handling the data to havean overall visual check on the information. The existing network should olso be takeninto account to assure that existing interface apparatus be used as much as possible.This would eliminate the purchase of special individual translating equipment to convertpaper tape to cards, magnetic tape to cards, paper tape to magnetic tape etc. Ifa system does not already exist and the number of installed analogue recorders is minimal,it would probably be preferable to initiate digital recorders which can eliminateall human processing of the record.The treatment of hydrological data in itself does not necessarily justify thepurchase or rental of expensive computers so that, before taking a~y decision, astudy should be made of the computer facilities availoble and their cost, and thepossibility of either adding to these facilities or instolling completely new mochineprocessing equipment.If the use of computers is contemplated it isrecording instruments should have an output compatiblefacilities.verywithimportantavailablethat newcomputer1.3 Factors affecting choice of instruments and type of installationfor automatic hydrological observing stationsIn the previous sections the odvantages and disadvantages ofbeen discussed. Once the decision has been made· to automate theautomation havehydrological

AUTOMATION OF OBSERVING STATIONS 5observations at an individuo~ station or 0 network of stations, careful considerationshould be given to the vorious foctors which will offect decisions on the type ofequipment to be instolled. In the following porogrophs, some of the constroints aredescribed. It is understood thot, where different instruments meet the users'requirements, the final decision will be based on the relative pric~ of the equipmentand its availability.1.3.1 Local conditionsAmong the more important and sometimes most difficult constraints whichusually have to be overcome are the local climate and physiographic characteristics atthe proposed observing sites. In many cases the final choice of equipment will, ineffect, be made solely on the capability of the instruments to operate underparticular local conditions.ClimateThe local climate, especially where extreme conditions are found, will havea considerable effect on the choice of instruments and types of installations. Forexample, in polar regions or cold mountainous areas, ice cover on rivers, frozenground, heavy precipitation ldeep snow cover, high winds and low t~mperatures mayrequire the use of specially designed equipment and non-standard installations.Instruments to be installed in such areas would have to be designed to assurecontinuous operation and recording under conditions where temperatures will descend to-400 C and often lower. Moving ports should not contract appreciably with the fallingtemperature; special lubrication should be used (in some cases designs necessitatingno lubrication at all have proved satisfactory); inks should be of non-freezing type(recording devices eliminating the use of liquids are usually preferable); and clockworksor other methods of chart movement have to be of special design to assurecontinuous operation. This latter problem is usually one of the most serious whichhas to be overcome in the operation of automatic equipment in the polar regions. Highwinds which are usually prevalent in these areas will necessitate extremely well constructedinstallations because blowing snow can completely fill the instrument shelterif even the smallest of openings is left in the walls of a shelter. Where instrumentsare partially in the water or on the river bed, the presence of ice cover willobviously affect the choice of equipment. In addition, as repair work during winteris practically impossible, this section of the equipment has to be extremely reliableand very well installed thereby minimizing failures.In order to overcome some of the difficulties caused by low temperatures,various methods for heating shelters have been developed. Where electricity isavailable, electric heating has proved quite successful. On the other hand, ininaccessible areas, different systems using propane gas heaters have been used withsome degree of success either to heat the interior of the shelter or an insulated areaaround the instrument. These heaters have not always proved completely reliable forlong periods of unattended operation. In addition, this type of heater usuallyrequires relatively large amounts of gas so that in remote areas they are fairlyexpensive to operate because of transportation costs. Condensation forming inshelters as a result of the gas combustion has also been a problem.

6 AUTOMATIC HYDROLOGICAL OBSERVATIONSThese are same of the factors which must be considered in the colder partsof the world. Similarly, extremely hot, arid or humid climates give rise to theirown peculiar sets of instrumentation problems. In all extreme climotes, on analysisshould be mode of the conditions which would affect the operation of proposed outomaticequipment. A valuable aid in this regard is the experience which has beengained by users of various types of : automatic equipment in similar location••Discussion with these people or reference to the literature may eliminate costlyerrors in the choice of instruments.The characteristics of the terrain in the immediote vicinity of the observingstation play an important role in the selection of equipment. For example, itwould be extremely costly to build wells to house water-level recorders near riverswhere waier-level fluctuations are quite large and the river banks are mostly bedrock.Wells will also be impractical where the river transports great amounts of sedimentwhich will continually block intake pipes. In these cases, a float-type gauge wouldnot be practical and instruments using the hydrostatic principle for detecting waterlevelchonges should be used.On the other hand, for rivers having moving beds, it mightany instrument having the detecting section in the stream itself ascarried away. An installation using a well and a float-type unwise to useit might bewould be moreFactors such as the geology of the local terrain and the presence of excessvegetation will affect the selection of the type of installation. Many instruments,in order to operate properly, have to be level, in which case the foundation of theshelter may have to be foirly elaborate in order to ensure that the structure is notaffected by changes in temperature, erosion or plant growth.In mountainous areas the installation of radio relay stations may be necessaryto provide for the transmission of the data. The initial and mointenance costs may bea significant factor in a decision on automation.Other conditionsIn urban and in certain remote areas, the problem of vandals can beserious and often may necessitate the use of special housing and equipment.addition, wherever possible, exterior portions of any installation should beto avoid tampering.veryInburiedWhen considering sites in inaccessible areas, difficulties and cost of transportation,in some cases, exclude the use of heavy equipment. In these c~ses, boththe type of installation and the instruments themselves should b: chosen w~th dueconsideration to weight and possible difficulties in tronsportat~on.

AUTOMATION OF OBSERVING STATIONS7Animals may prave to be a problem in certain areas and, if so, suitableprotection should be included in the installations.1.3.2Many of the installations which will be considered in connexion with theautomation of hydrological obser/otions will imply the use of electric power forsensor purposes, chart movement, heating or data transmission. This is one of themost important and sometimes most difficult considerotions in the choice of equipment.If power is available locally, the choice will be relatively simple but, even so, astandby system of batteries may be necessary. This will be the case when, forexample, the observations are being used for flood forecasting and where, duringextreme floods, power lines could often be broken. In order to assure uninterruptedobservation of data during these critical periods, a standby battery system isessential.If no commercial power is available other sources such as wind-generators,fuel-driven generatars and batteries should be considered. As a first step, a carefulevaluation of the energy consumption of the observation system should be made.ObviouslYt continuous transmission of data will appreciably increase the power consumption.As the use of more sophisticated power supplies, such as generators,involves the possibility of mechanical failure, it is generally preferable, whereverpossible, to employ low-consumption equipment which would permit the use of batteries.The batteries should be carefully chosen to ensure reliable operation under differentclimatic conditions, especially in extremely hot or cold temperatures. Rechargeablebatteries usually involve a large initial expenditure as well as relatively frequentinspections. For most recording instruments, non-rechargeable batteries are available,if required, which guarantee approximately two years of operation beforereplacement.At present, it is very difficult to obtain recording and transmitting equipmentas well as power supplies which will completely answer 011 the problemsencountered at ony one site. It should be understood by the network planner thatlocal modifications will almost invariably be nec~ssary to meet the particularcombination of problems arising from both local conditions and power demands.1.3.3As hydrological observing stations are installed primarily to obtain data tohelp ensure proper use of water resources, it is evident that the accuracy of themeasurements should meet the standards of those who use the information. Cost ofequipment usually varies directly with its accuracy. Therefore, excessive demandsover and above the accuracy needed by the data users would, in effect l be a waste offinancial resources. This is elso true when the G~curacy demanded from one part ofan observation programme is out of proportion with the results obtained in the overallprogramme.During the design of an observing proglomme it is therefore obvious that astudy should be made regarding the accurocy needed by the users, both present and

8 AUTOMATIC HYDROLOGICAL 08SERVATIONSfuture, as well as of the overall accuracy possible in the various components of theprogramme. Two basic elements should be considered in this regard; firstly,instrumental accuracy in the measurement of the parameter, and seco~dly, timeaccuracy and resolution. The former would affect the choice of sensor and recordingsystem while the latter will govern the selection of the type of clockwork and chartmovement.When considering water-level~tqg~observationsfor eventual conversion intodischarge data by means of a stage-discharge relationship to be determined by streamgauging, thought should be given to the following points. As the effects ofinaccuracies in water level are relatively less significant at high stages than atlow stages, it is important to decide whether the station is to be operated to supplylow-flow or high-flow information. In addition, it would be useless to considerhigh accuracy equipment for the water-level measurement if local conditions da natpermit precise stream discharge measurement.This does not preclude the possibility that data users, by justifying theneed for more precise data, would make it necessary to develop more acc~rate streamdischarge measurement (even at a relatively high cost). In view of this, betterquality stage records should be part of the initial programme.If, far certain reasons such as back water from ice and weeds in the controlsection, precise calculation of discharges using water-levels is impractical,excessive disbursements of money and effort to obtain very accurate levels are notjustified. In general, the highest accuracy (at least ± 0.003 metres) is usuallyneeded where the aim of the observation is to obtain short duration low-flow data onrelatively small streams. Data requirements such as monthly means or flood flows onvery large rivers do not need extremely precise water-level data (better than ± 0.03metres), although for establishing peak flows for use in numerical analysis greaterprecision for measuring flood flows may be necessary. If equipment is to cover thecomplete range of stage, it must obviously satisfy the most demanding conditions.1.3.4If a station is to be operated for a relatively short period of time, sayone or two years, it would be desirable to select equipment and a type of installationwhich can be easily moved. In other words, if possible, permanent structuressuch as wells and expensive shelters should only be used where long-term observationsare planned.1.3.5 MaintenanceIn order to derive maximum benefits fromcomplete maintenance of instruments is essential.proper maintenance each have their own effects onany observing programme, regularVarious problems associated withthe choice of equipment.The interval between inspections will largely depend uponthe type of equipment and the seriousness of any loss of record.local conditions,The length of

AUTOMATION OF OBSERVING STATIONS 9unattended aperation will in turn have its effect on the choice of clockwork and typeof recording (ink, pencil, special paper, etc.). Instruments where charts will bechanged once a week can have a relatively simple clockwork while stations visited ona six-monthly basis would require instruments with relatively complicated andexpensive clockwork. As to the problem of loss of record, it is.· sometimes moreeconomical in extremely inaccessible areas to have duplicate installation to permitless frequent expensive inspections and at the same time ensure a minimum loss.It is preferable that there be uniformity in the type of instruments used ina network. This would simplify the work of the technicians who have to make repairsand would make the stocking of spare parts less complicated. In· this _egard, itwould be preferable to use relatively simple and standard equipment so that spareparts are available on demand.It is also desirable to select an instrument that may be repaired in thefield if necessary with makeshift tools and parts.It is important that the availability of spare parts is assured for thewhole life of the stations. In certain cases, in the past, because a type of instrumenthas become obsolete, it has become extremely difficult and expensive to obtainreplacement parts for those already installed.PersonnelIt is essential that competent technicians are available to perform theregular maintenance needed. If such personnel are not available a training programmeshould be started as soon as a decision is made to install the relatively complex 'equipment associated with automation. The competence of the actual or proposedpersonnel will be a factor in deciding upon the complexity of the equipment to beobtained. It would not be sensible to acquire instruments which, because of theircomplicated workings, could not be repaired by the available personnel.It must be stressed that the decisions made have to be long-term; that is,maintenance must be part of the programme as long as it exists. As automatic instrumentswill not operate indefinitively without proper care, no matter what. type ofequipment is chosen, a breakdown in maintenance will result in a high capital expenditurewith little useful return.1.3.6Any decision regarding the type of recorder to be used will have to take intoconsideration the speed with which the data is wanted by the user. If there is noneed for immediate information, an instrument can be installed and the recorded datacollected at any interval, either by a local observer ar by· a visiting technician.On the other hand, if data are required immediately as the parameter varies or when itreaches predetermined limits, this might necessitate automatic transmission of thedata. This aspect af autamation is discussed more fully in Chapter 2, especially asta the decisions affecting the choice of mode of transmission. These decisions will

10 AUTOMATIC HYDROLOGICAL OBSERVATIONSnaturally influence the choice of automatic detecting and, if necessary, recordingequipment. There are cases where no local recording is deemed necessary as theinformation is fed continuously into a central computer.It should b~ noted that even.though immediate transmission of data may notseem essential at the moment, future needs should be considered carefully to avoidhaving to change equipment if and when the need does arise. On the other hand, theuse of automatic recording equipment compatible with automatic transmission generallymeans using more complex instrumentation. As this equipment requires highly skilledtechnicians for maintenance as described in the previous paragraph, this could provea serious constraint in any selection.1.3.7 Treatment of dataTreatment of data as a factor affecting the choice of instruments andinstallations for the automation of hydrological observing stations has beendescribed in paragraph 1.2.2 above.1.4 Selection of instruments1.4.1 ~:!~~:~_~:~~2~The design of a hydrological network must provide for the collection of allpertinent data to satisfy the purposes of the programme. Thus a key element in theselection of instruments is the network design. Regrettably, design of hydrologicalnetworks has received comparatively little attention and definitive approachesto the problem are not generally available. To help overCome this deficiency, theWMO Commission for Hydrology has prepared a "Casebook on hydrological network designpractice" (WMO - No.324) which includes theoretical and practical examples of networkstogether with explanatory notes on objectives and principles used. The WMOhas also sponsored and collaborated on several papers on network design, including:Hydrologic networks and methods. Flood Control Series ReportNo. 15, WMO/ECAFE, Bangkok, 1960.Design of hydrological networks, WMO-No.82.TP.32, 1958.Proceedings, WMO/IASH Symposium on the Design of HydrologicalNetworks, Quebec. lASH Pub. No. 68, 1965.Hydrological network design - Needs, problems and approaches.WMO/IHD Report No. 12, 1969.1.4.2 Aids for selection of instrumentsGeneral guidance pertaining to instruments and methods of observations iscontained in WMO "Guide to hydrometeorological practices" and WMO "Guide tometeorological instruments and observing practices". Although the material in theGuides is specific as to the type of instruments required, no information oncommercially available instruments is included. Another source of general informationis WMO/ECAFE Publication No. 22, "Field methods and equipment used in hydrologyand hydrometeorology".

AUTOMATION OF OBSERVING STATIONS11The most complete reports on commercial : instruments are available inbrochures published by the various instrument manufacturers. Mast companies haverepresentatives who, upon request, will submit proposals for instruments to meetdesign specifications by a planning agency.1.4.3 Questionnaire on instruments of proven reliability--------------------~-----------------------------The WMO Commission for Hydrology also directed its Rapporteur on Instrumentsto solicit information from Members on instruments of proven reliability that couldbe consolidated into a report for use by Members and others as an aid in selectinginstruments for establishing hydrological networks.The Members furnished information as specified by the questionnaire (seeAnnex 1) for those instruments which have been tested and proven reliable underactual operational conditions. Requested information included the name and addressof the reporting organi~ation, detailed information on the reported instrument,operational experience, environmental conditions under which it has been operated andcost data for the basic instrument and for equipment required for transmission ofreports. Details of new instrument development were also reported.Some 220 responses were received from 31 Members. The replies were fairlyrepresentative for all requested categories except (c) instruments for meteorologicalelements at floating stations for energy balance or mass transfer estimates ofevaporation (see Annex 1).The responses did not include some instruments that are known to be of provenreliability. However, they did include many of the instruments in use in the basicdata networks of Members.Tables prepared by the Rapporteur containing selected information on theinstruments of proven reliability are contained in Annex 2 for all categories except(c) mentioned above. Included in the tables are data on some instruments which werereported as under development or in limited use.Additional information, if desired, on any of the reported instruments maybe obtained upon request to the WMO Secretariat.1.5 Special considerationsThe rapid development in the fields of instrumentation and transmissionsystems makes it extremely difficult for even those most active in the fields to keepabreast of recent improvements and innovations. Direct contact_ with the manufacturersand agencies conducting research and development is the most reliable ~ethodof keeping informed but potential users should be aware that many new instruments andtransmission systems are generally plagued by technical difficulties during the firstfew years of field test and use. Unless a user is willing to accept the possibilityof economic loss and a delay in achieving operational status, he should rely on thoseinstruments and systems which have proven to be reliable in field use or in nationalnetworks under environmental conditions similar to those anticipated for his area.

12 AUTOMATIC HYDROLOGICAL OBSERVATIONSThose who consider the development of new instruments or transmission systemsof their own design should recognize the high cost generally ossociated with suchresearch, test and evoluation activities. Initial estimates of costs for suchdevelopment are often much less thon the finol cost to perfect an operationallyacceptable instrument or system.

C HAP T E R 2TRANSMISSION OF HYDROLOGICAL OBSERVATIONS2.1 IntroductionDuring recent yeors, the demonds of users of hydrolgicol data have becomemore and more sophisticated so that the system where an observer makes manualmeasurements of rainfall, water-levels etc. and then mails the results to the analystis becoming more and more obsolete. The need for data has extended to inaccessibleareas where up to now no information has been available. In addition the insistenceon higher quality information as well as rapid receipt of this information has resultedin drastic changes both in the methods of measuring as well as the means of tronsmittingdata.It is well to note that these recent innovations are relatively expensiveand, in cases where daily readings by a local resident meet the requirements, this maystill be the least expensive operation. On the other hand, as stated above, moderndata requirements eliminate this procedure as an alternative in many cases tand callfor more complicated and expensive measuring stations. It is therefore essentialthat the network planner determine at the outset precisely the type of data he wishesto collect as well as the delay he can tolerate in the use of the information. Theserequirements should be examined attentively when comparing the cost and the outputof different possible systems before making any final decision as to the type ofinstallation to be used.2.2 Systems of data transmissionThe possible methods of transmitting hydrological data are given below in avery ba~ic form, together with comments on their advantages and disadvantages.SYSTEM 1Form of telemetered or telephone call toand supplies instantaneousObserver at station mails data or initiatescentral office based on pre-arranged criteriareadings onlyAdvantages. Simple sensoring equipment may be used and malfunctionof sensor is known immediately. Inexpensive (communications paidfor only when used). If necessary can be interrogated from centralofficeDisadvantages. No automatic recording so that continuousnot available. Quality of observer extremely important.or radio link overloaded at certain critical periodsrecord of eventsCentral phoneRemarks. Phone calls can be received and recorded automatically on anlIe l ectronic secretary" and transcribed at any time.

14 AUTOMATIC HYDROLOGICAL OBSERVATIONSSYSTEM 2Form of telemetered data. Central affice interrogates by phone, radioor radio telephone, remote automatic station and receives single discretevalues as often as interrogated. It is possible to have an automatic diallingdevice in the control office which could interrogate and· record responsesat regular intervals·Advantages. Instantaneaus infarmation can be obtained as required even inisolated areasDisadvantages. No continuous record. Difficult to determine malfunctionof sensors. In addition to radio or telephone, equipment at station requiresa device to answer calls for information automaticallyRemarks. Method of answering can be voice recording, short ·tones forhundredths, tenths, units etc. or one continuous tone the length of which isa function of the value (less accurate). In some instruments a memory canbe included so that upon interrogation continuous or extreme data can bereceived for a pre-determined period prior to the call. Cost can vary from·$1 000 to $5 000 depending on complexity of system. When using FM radio thecost of radio antennae is normally the main portion of total cost particu~larly at remote and distant sites.SYSTEM 3Form of telemetered data. Automatic station programmed toinitiate phone or radio call to supply particular single instantaneousobservationAdvantages.Immediate alert of extraordinary hydrologic conditionsDisadvantages. No continuous record.sensors. Specia~ device necessary tocriteriaDifficult to determine malfunction ofinitiate calls based an predeterminedRemarks. As this system is normally an alert-oriented unit, it is usuollyon a private line to a receiver who is always on call.SYSTEM 4Form of telemetered data. An impulse is transmitted automatically by phoneor radio for specified unit of change of porameter (each centimetre of changeof water-level for example)Advantages.Complete record of change of events as they occurDisadvantages. Malfunction of sensors can be detected only after a certaininterval of time (for example; due to malfunction no change detected inparameter and therefore no signal emitted). Reliable power supply very important

TRANSMISSION OF HYDROLOGICAL OBSERVATIONS 15Remarks. Infarmation received usually recorded on a graphical or digitalrecorder at central station. Cost of equipment (using rental telephone lines)approximately $3 000 plus telephone line rental usually based on distance.SYSTEM 5Form of telemetered ,data. An impulse is transmitted automatically by phoneor radio'at predetermined 'intervals of timeAdvantages.Disadvantages.A total record is obtainedReliable supply power very importantRemarks.teletypeThis form of in-formation transmissionor satellite especially suited forSYSTEM 6Form of telemetered data. A combination of systems 4 and 5 is possible;that is, unit changes in the measured parameter are stored and transmittedat set intervals of time.SYSTEM 7Form of telemetered data. Data are transmitted and recorded on a continuausbasis through electrical wires fram a device that' produces an electricalsignal in proportion to the value of the parameter being monitored (analoguetransmission)Advantages.Disadvantages.feet maximumA total record is obtained immediatelyDistance from sensor to user is limited to a few thousandRemarks.Normally each sensor is connected to a separate receiver.SYSTEM 8Form of telemetered data. Data ore transmitted on a continuous basis overradio or telephone by equipment that converts observations to a continuoustone or frequency. This information is reconverted at the receiving site(frequency modulation)Advantages.A total record is abtained immediatelyRemarks. Systems using telephone line can cover any distance through theuse of signal repeaters (amplifiers) along the way. FM radio usuallyapplies to line-of-sight distance only. AM radia can be used over greaterdistances but is more subject to atmospheric interference.

16 AUTOMATIC HYDROLOGICAL OBSERVATIONSSYSTEM 9Form of telemetered data. Remote field sites equipped with data sensors,encoder and radio transceiver transmit coded information to a central officewhere information is decoded and fed to a computer which has initiated thesequential callsAdvantage.System is completely automaticDisadvantages.Very expensive and complex to serviceRemarks. S~stem usually included programme where . predeterminedobservations are brought to the attention of the system operator.links or orbiting Earth satellites can be used for transmission ormission.2.3 General considerations in selection of systemsextreme. FM radiore-trans~.When considering the possibility of including automatic transmission of datain any measuring system, consideration should be given to the following:(i)Accessibility or inaccessibility of the measurement sites}Obviously where a statian is located in an area where accessibilityis extremely difficult and expensive, it would probably be preferableto have automatic recording as well as telemetering of the data.(ii) Reliability of alternative recording device;In certain cases, because of rigorous local climatic conditions, the operationof on-site mechanical equipment is difficult and it is more reliable simplyto transmit information electronically to be recorded in a central climate con_trolled office. In addition, this type of system permits a continuous check ofthe operation of the sensors. .(iii)Speed with which data is required;(a)(b)(c)(d)Time between observations and receipt of the data by the analystTime required to procees and analyse the dataSpeed with which changes in the parameter take place and whateffect these parameters have on the regime in questionAccrued benefits of forecasts from telemetered data as well ascost due to lack or delay of knowledge.(iv) Staffing and logistic problems;Localobservations or a surveillance of. on-site recording equipmentrequires qualified personnel in the vicinity of the measuring station whichimplies a relatively large number of qualified personnel. On the other hand,a centrally controlled telemetering system would necessitate the use of a very

TRANSMISSION OF HYDROLOGICAL OBSERVATIONS 17much smaller proportion of technicians versus number of measuring stations, eventhough this latter personnel would have to be very highly qualified.These are some of the more important criteria to beplanning process but each individual project will have its owncareful attention should be given to all the alternatives withfits before any final decision is made.considered inparticularitiestheir costs andtheandbene-When designing a system for the automatic transmission of measured data, thethree main components to develop are:(a)(b)(c)Measuring and encoding equipment;The transmission link;Receiving, decoding and analysing.While developing each of these units separately, it is necessary to considerthe three together in the design stage. This is essential as the special characteristicsof anyone of these components can have serious Gonsequences on the decisionsregarding the others.The type of installation for measuring and transmitting the data will dependgreatly on the parameter or parameters to be measured especially as regards theirvariability with time and space, the climate in the area which would affect the choiceof sensor, power supply etc. and the type of transmission to be used witb considera~tion given to the distances to be covered.2.4 Transmission linksThe type of transmission link used is determined by the frequenQY bondrequirements and economics. Availability locally of anyone of the alternate choicesis a constraint. Possible choices for transmission links include: dedicated landlines, commercial telephone or telegraph lines, direct radio links, satellite retransmissionsystems.2.4.1 Dedicated land linesThese are perhaps the easiest to install when relatively short distances areinvolved and no commercial lines already exist. Land lines are typically able totransmit frequencies of up to 3 000 Hertz* without special techniques. Time divisionand frequency multiplexing** can be used to provide more economic use of the tronsmissionline.* Hertz is a unit of frequency.** The process of using one transmission line to transmit several measurements iscalled multiplexing.

18AUTOMATIC HYDROLOGICAL OBSERVATIONS2.4.2When the distances invalved are lang and existing telephane systems exist,usecan be made af these. Equipment exists to enable the instrument to simulate thebehaviour of a relatively normal subscriber to the telephone service. Measurementsand commands can be transmitted to and from the remate site.2.4.3The use of commercial telegraph lines to transmit data on request from a remotesite is illustrated in Figure 2.1.Tope advance . 3control linesCommercial teletype networkPaper tape loopextended outof recorder".";-32Leaend1 _ Punch paper tope water-level recorder, float operated2 - Teletype tape reader head3 _ Teleprinter4 - Punch tope 'output5 - Hard copy printoutFigure 2.1 - Teletype equipment system. The system works asfollows: the operator activates the recorder tape advance tobring the last data punch within range of the reader; then thetape reader is activated; data on tape are transmitted viateletype lines to the receiving equipment; autput appears as aduplicate of the punched paper tape record gathered unattendedon site as well as a print out of the data

TRANSMISSION OF HYDROLOGICAL OBSERVATIONS192.4.4Direct radia linksThese must be used when the data frequency requirements exceed thase availableover land lines.or when distances ar natural obstacles prevent the economicinstallation of wires. Distonces of kilometres to hundreds of kilometres may bespanned by radio transmitters, depending upon the frequency and power avoilable: Atthe higher frequencies, the tronsmitter and receiver must have a cleon line-of-sighttronsmission path. This limits the range without repeater stations.In all cases, installation and operation of radio transmission links isgoverned by national and international regulations.2.4.5 Satellite linksData transmission from satellites can take place in two ways;of data as observed by sensors in the satellite (including photogrophs)data observed at remote ground stations to central receiving locations.transmissionor by relayingAt present, the science of observation and transmission or retransmissionfrom satellites is developing rapidly and during the next few years, enormous amountsof data will be available either directly from the space craft or through central databanks. The Geostationory Operational Environmental Satellite (GOES) System scheduledfor launch in 1972 is an important addition to the World Weather Watch network. Thissystem is a good example of the two types of transmission mentioned above, and moredetailed information is available from the Director, National Environmental SatelliteService, National Oceanic and Atmospheric Administration, Washington, D.C. 20031,U.S.A.It should be noted that the METEOR meteorological space system has alreadybeen established and is operating successfully in the Soviet Union. In the METEORsystem orientations are used in relation to the centre of the Earth and the course ofthe satellites. The satellites contain apparatus for collectian and tronsmission ofinformation; the system also comprises a surface network for the collection, processingand dissemination of information obtained from the satellites including receivingstations, recording apparatus and data-processing machines, including electroniccomputers.More detailed information about this system and the results of its utilizationare available in the report IIProgress in the use of data from satellites in theHydrometeorological Service of the U.S.S.R.'~ which can be obtained from the WMO Secretariat.2.5 Receiving systemThe eventual use of the data will govern the type of equipment needed for thereceiving end of any automatic transmission system. In a relatively simple system,regular calls- by the analyst to the measurement site coupled with simple analyses couldbe sufficient. On the other hand, in complex situations where complicated analysesprecede rapid decisions, it might be necessary to couple continuous transmissionsthrough the necessary decoding system to a computer which would be programmed to makethe required decisians. Added to this could be a system for alerting certain designatedpeaple in such cases as flood or typhoon alerts for example. Figure 2.2 is

20 AUTOMATIC HYDROLOGICAL OBSERVATIONSthat af a system where anly extraardinary events are telemetered.order to eliminate continuous transmission on telephone lines thevery expensive.This is done inrental of which isIJ\MnnJLJUlIlIL,----------.-'-------··--1IIIIIIt~-81-IIIIII___ l ~Legend1 _ Data transmitter. Analogue waterleveldo to are converted into electricaldigits2 _ Memory unit which con store minimum ormaximum water-level information and tensuccessive water levels3 _ Dialing unit which automatically callsa predetermined party in the event of anunusual water_level condition4 _ Announcing unit which when addressed,announce5 the existing water-level,the rising or falling tendency, thelost high or low water or any of theother stored doto5 _ Tilller6 _ Punch paper tope recorder7 - Power supply unit8 _ TelephoneFigure 2.2 - Tele-announcing system. The system works as follows:the tele-announcer is installed in place of an ordinary telephoneset and addressed by dialling the number of the telephone line. Inthe case of an unusual water-level change, the dialling unit producesa series of pulses corresponding to a codified call numberand switches on the tele-announcer. On receiving a call in thecase of an unusual event! a punch paper tape recorder is activatedto store over a pre-set time period the water level changes at oneminuteintervals. These data are available to the authorities concerned,or shortly after the event

C HAP T E R 3EXAMPLES OF AUTOMATIC TRANSMISSION SYSTEMS FORHYDROLOGICAL PURPOSES3.1 Example I (Canada)The following is an excerpt from a report written in 1969 by H. C. Belhouse,D. W. Colwell and J. S. Dickson, Meteorological Service of Canada, describing theapproach taken by this organization in the development of hydrometeorological automatictelemetering stations in the Columbia River basin of Canada.At the beginning of our study, very little work wos being done in outomaticreporting of hydrometeorological parameters. The sensors available were principallydesigned for local recording. Also, in the commercial equipment available, a gapexisted between heavy industrial and sophisticated space-oriented techniques, neitherof which was suited to our needs.Without available equipment specifically designed for our requirements, therewas little choice but to undertake the task of filling this gap ourselves. This meantthat it would be necessary to set out from basic principles in assessing our mountainenvironment and in discovering what equipment would be most reliable under these conditions.The approach taken was to begin with existing, simple equipment, with no illusionsof immediate success. At best what was hoped for was a fuller understandingof the environment and related equipment problems, to yield more specific objectivesfor later development phases.In basic concept, the system would consist of a self-powered and unattendedremote station on a mountain observing site which would automatically measure andtransmit data by radio link to an attended base station where the report would be automaticallyrecorded.Assumed requirementsEnvironmental implications~ Certain assumptions had to be made about themountain environment, as a basis for initial design: operating ranges were establishedfor temperature (-40 0 F to + 120 0 F), wind (120 miles per hour), snow loads (100inches of water equivalent) and icing of radio antennae and towers (2 inches).Reporting of parameters. The system was intended to report precipitationand temperature data which could be used to estimate mountain runoff into the Columbia

22 AUTOMATIC HYDROLOGICAL OBSERVATIONSRiver watershed. The requirement was for up to eight reports per day of accumulatedsnowfall (water equivalent to ~ 0.1 inches) and of ambient temperature (± 10F).Siting implications. A primary objective was that the observing site berepresentative of the' snowpack oreo in question. The measurements were to be madein a mountain meadow below the tree line with good drainage, minimum drifting of snowand low avalanche hazard. Since line-of-sight radio transmission to the base stationwas almost surely a necessity, a remote location meeting all these conditions wouldprobably be hard to find, and .not easily accessible. Installations would thereforebe difficult if the equipment was not easily portable, at least by helicopter. Asfrequent maintenance visits would be costly and impractical, the remote station wouldbe required to operate reliably and unattended for periods of four to six months.Base station. It was assumed that a base station, suitably located forline-of-sight radio reception, would be served by telegraph or other primary communications,for manual relay by the local operator of the automatically recorded data transmittedfrom the mountain site.In parallel with the undertaking of long-term design and development, arecording precipitation gauge was installed on Mt. Fidelity in British Columbiaduring the winter of 1963-64 for an initial assessment of environmental problems.The gauge, with an Alter shield attached, was placed twelve feet above the groundon a metal tower.The outcome of this experiment was an unquestionable verification of ourfears that wet snow clings tenaciously to rough surfaced gauge housings and chainedAlter shields, causing IImus hroom" overcopping of the gauge orifice and rendering thegauge completely inoperative.Having a technique with which we hoped to overcome this problem, we then proceededto assemble existing sensors, encoders, radio and power supply equipment intoa first prototype telemetering system.The dial pointer position of a Taylor mercury-in-steel thermometer and therecorder pen arm position of a Leupold and Stevens telemetering precipitation gaugewere detected by follower devices, servo-driven by Telemark drum encoders. Data fromthese encoders were transmitted by IItaxi ll radio equipment to a strip-chart eventrecorder.The power consumption of the radio transmitter was such thatbattery would not be sufficient. A thermo-electric generator consumingpropane per year was added to replenish the battery charge continuously.a lead-acid400 pounds ofThis equipment was housed in a sectional fibreglass dome eight feet in heightand diameter, which was complete with ventilation pipes for the generator and a fourfootstack protruding through the roof to allow precipitation to fall into the gauge.

EXAMPLES OF TRANSMISSION SYSTEMS 23The stack was tapped by a three foot metal cone, blackened and ~ silicone-treated toavoid snow adhesion, and having a ten-inch orifice at the top.The entire ossembly was to be installed above the maximum snow level on awooden platform, to allow access for servicing.In a pre-assessment of this configuration, the complete system was evaluatedat our Toronto test site, while a second dome, with stack and catch cone and a precipitationgauge were installed on Mt. Fidelity to provide ~information on environ~mental effects.Results. This strategy proved worthwhile in the early identification ofserious shortcomings of the system, making possible major redesign of these criticalareas before engaging in an arduous mountain test programme.The propane power supply was cumbersome and in fact unreliable, and all laterequipment was redesigned for minimum power consumption to allow the exclusive use ofbatteries.The precipitation gauge did not adequately represent the snow on the groundand was inaccurate even when an Alter shield was employed. More promising snow-ongroundsensors were later used to replace the gauge.While the silicone-treated catch cone appeared to remain free of snow, theaccumulation on the dome itself and on the support tower threatened to overcap thegauge orifice. The deletion of the power generator and the precipitation gauge laterallowed a great reduction in shelter and support size.To aid the full system redesign which was progressing at the Toronto laboratorythis first telemetering prototype with a few important changes, was installedduring the winter 1965-66 on a mountain meadow near Enderby, British Columbia.A low power solid state radio transmitter allowed operation of the remotestation with a lead-acid battery, and further mountain environment and telemetry linkchecks were possible.The Enderby tests showed that radio telemetry and battery power were feasible.The precipitation gauge however underweighed the snow as it had done at Toronto, andhigh snowfall rates caused some pile-up in the gauge because of surface dilution of theantifreeze.March,cone.woodenThe silicone treatment of the catch cone again avoided snow adhesion, but bybuild-up on the dome itself had reached to within six inches of the top of theComplete overcapping of the orifice was only averted when the collapse of thetower under the extreme snow load terminated the winter's test.Following the investigation of experimental problems with available hardware,the next two years were devoted to the identification of more suitable instrumentationfor a final prototype. Various sensor alternatives were explored, component models

24 AUTOMATIC HYDROLOGICAL OBSERVATIONSwere constructed and mountain tested. In this process there were several failures,but each led to a better understanding and subsequent approach to the problems involved.More favourable sub-units slowly emerged, were refined and adapted into agradually improving prototype system. Some of the approaches used in this process,and the results and experience gained thereby, are worthy of note.Tubular steel anemometer towers, suitably guyed, were used for basic supportingstructures, with functional equipment mounted in weatherproof boxes well aboveground to be clear of, or easily accessible through, the higher winter snow level.It was found however that forces were exerted on the 3/8 inch stranded steel guys byadherence, compaction and steeling of the snowpack itself, to the extent that some guysbroke, and others caused local bending of the tower as much as a foot off the vertical.It was faund that linear thermal contraction af the guy wires accentuated this problemgreatly and that leaving sufficient slack at the time of installation removed thefault.Nickel-cadmium batteries and lead acid cells both proved unsuitable as powersupplies, because of current leakage to ground and high degree of susceptibility todamage even with careful handling. It was nevertheless felt that batteries of suitabledurability and performance still remained the only feasible answer to the powerproblem.With electronic equipment, three major problems arose. Ever-present humiditycaused extreme corrosion of normal contracts and connexions, calling for bettermaterials and protection, and electronic design less .. sensitive to this problem.Several components considered and even specified as suitable for particular applicationssuch as low temperatures were in fact found to be very critical for theseapplications and had to be re-selected. Fail safe devices installed for systemreliability resulted in some cases in causing system shut-down themselves, and had tobe refined for proper performance and better indication of system malfunction.On the more positive side, the introduction of solid state programming andcontrol and use of binary-coded-decimal transmission showed immediate benefits inreliability, flexibility and lower power drain.~u:r:n!~p~r~a:hThe pratotype equipment now under test at the Enderby· site represents afeasibility model of final system design, based on the concepts evolved during ourstudy. The prototype incorporates our best solutions thus far to the problems encountered,and is designed to provide not only a reliable but also a versatile system,capable of wide application to remote sensing needs.Components which survived the evolution stage have been retained, such as thesnow pillow, the tipping bucket raingauge, the radio equipment and the chronometricclock which iriitiated transmission.Sub-units which have been refined or completely modified include: supportstructures, sensors, analogue-to-digital devices, telemetry control and programming,power supplies and recording methods.

EXAMPLES OF TRANSMISSION SYSTEMS 25Support structures. The remote station equipment other thon sensors andantennae is enclosed in weatherproof metal boxes, which are presently mounted at thebases of the most resilient, unguyed, ground-rooted towers we were able to supply athand-toPPed-and unlimbed trees. The above snow sensors and the radio antenna aremounted above the maximum expected snow level.Two coi1CejJf:s here are 'worthy of note. _. 'Firstly, the- placing of equipment onor even in the ground reduces tower loading and the snow cover provides good protectionfrom the environment. Secondly, while our use of trees os towers is notnecessarily advocated for long-term application, we feel that permonent structuresshould be designed with parollel characteristics and performance.Sensors and encoders. While the raingauge and snow pillow have been retoin~ed from earlier models, the thermistor and its onalogue-to-digital encoder, and thepressure detector and encoder for the snow pillow are new designs and show greatpromise.The temperature encoder is a simple electronic device. for digitizing ofresistance and appears to be reliable. Accuracy and linearity of this unit will beimproved before inclusion in the final system.The snow pillow pressure digitizing encoder in this model is very good. Thedesign is essentially based on that of an open mercury manometer, employing a servodrivenmicrometer lead screw to detect mercury level.Programmer control. The readout of sensors, digitizing and scanning of dataand format of sequential transmission of information is directly controlled or accomplishedby a solid state programmer, the design of which is based on digital computerlogic functions.Power supply. Alkaline "dry" electrolyte primary cells make up the batteryused to supply the remote station. These batteries are efficient at low temperatures,and are capable of operating the system for up to two years, depending on the frequencyof reports and the number of batteries used.Recording. An automatic electric typewriter equipped for computer-typedata input is employed at the base station to record both telemetered data and date/time information provided locally. The design of the telemetry link/recorder interfaceequipment is based on the same logic functions as the remote station programmer,and effectively reverses the role of that equipment by converting the sequentialbinary-coded-decimal transmission of data into parallel output for the typewriter.Results. Outside of one period when records were interrupted by failure ofthe printer input power supply at the base station, operation of the system has beenvery satisfactory. The remote station did fail to transmit data for one two-dayperiod, but it was found that the ambient temperature had dropped below the designoperating minimum of _30 0 Fahrenheit. As soon as the temperature rose above thatpoint, normal operation was resumed automatically.From our point of view, however, the most encouraging feature of theis the proving of the inherent reliability of the remote station equipment.systemAt the

26 AUTOMATIC HYDROLOGICAL OBSERVATIONStime of writing, no basic failure has occurred after over four months of continuousoperation.ConclusionAt this stage, the specific purpose is to report snowpack parameters, fromremote mountain areas in the Columbia River watershed, to a manned base station. Thesystem as it stands will report up to three parameters, and will produce a record onelectric typewriter or punched paper tape.The telemetry system is simple and versatile, however, and is adaptable toalmost any dedicated communications link: direct radio transmission, landline, telephone,or any combination of these. It will also be possible to provide thefacility for operation with existing land-line or radio teletype networks.As the system is modular, it is possible to add other parameters to itsreport: wind speed and direction and total precipitation are examples where existingsensors can be incorporated, along with suitable encoders. Reporting of other parometerswill be feasible when reliable - low-power sensors become available. Forexample, a simple humidity sensor not susceptible to contamination would be a· verywelcome addition for many purposes.The aim of such system versatility is to provide wide applicability to meetother needs. Few, if any, of these will . impo~e such formidable constraints ofenvironment and long term reliability as those of the mountain stations for theColumbia network, and in most cases the modular equipment will then constitute on easyand direct solution to the problem. Design features and components of· this equipmenthave already been adopted in the development of a remote wind reporting stationon the Queen Charlotte Islands. Distinct opplications are foreseen for forestrypurposes as well.Such equipment should now easily meet the needs expressed to MeteorologicalBranch for hydrometeorological reporting from other major river basins. The equipmentcould also accept hydrological inputs such as water-level sensors, and could infact be used to upgrade existing hydrological recording networks into telemeteringnetworks of both hydrological and hydrometeorological data.3.2 Example II (U.S.A.). The Hy-Tel remote radio telemetry systemSince September 1968, the Notional Weather Service of the United States hasoperated experimentally a hydrological telemetry network in the American River Basinof California. This system, known as Hy-Tel (Hydrologic Telemetering), is manufacturedby the Astro-Met Division of Thiokol Chemical Corporation of Ogden, Utah,U.S.A.The network provides precipitation, temperature and snow water equivalentdata for use in river, flood and water management forecasting. Sensors for otherparameters such as wind direction and speed, dew point, radiation, etc. are beingdeveloped. The system is designed to read up to 22 separate sensors.

EXAMPLES OF TRANSMISSION SYSTEMS 27The basic philosophy in planning the Hy-Tel system was that the remotestations b~ kept as simple, inexpensive and as reliable as possible. The basestation at Sacramento, California consists of a console with digital readout, a radiowith antenna and a radio remote unit. The base station, which will normally be in aconvenient location and a controlled environment, will contain the bulk of thesophisticated equipment.The present readout is manually controlled. Code buttons are punched foreach remote data station and the data is presented visually by numbers which light upon the control console, after the call button is pushed. A more sophisticated readoutis available at added cost which will call up the data stations automaticallyon a programmed time basis and print out the data on a teletype machine.Hy-Tel is a complete system. It includesbut all the components of a data collecting system;d~cers, antennae and towers -(se~ Figure 3.1).not only the radioincluding gauges,telemetry link,sensors,- trans-To maintain the simplicity of the remote station, the data is kept in analogueform until it is received at the base station. The data at the remote stationis represented by the frequency of an audio tone. As the measured parameter changes,the frequency of the tone changes. The audio tone, in turn, frequency modulates theradio frequency carrier. Thence, the system is a VHF FM-FM telemetry system (UHF isavailable as an option). The data is conveyed to the base station on an r-f carrierwhich is frequency-modulated by a subcarrier which is in turn frequency-modulated bytransducers at the remote data station. The r-f carrier is demodulated by the basestation receiver, and the frequency modulated subcarrier is presented to the subcarrierdiscriminator. The output of the subcarrier discriminator is a DC voltagewhich is digitized by a Digital Voltmeter (DVM) and visually displayed as a numberbetween 000.0 and 100.0. The number is interpreted as a- percentage of the fullscale of the parameter being measured; i.eo, if temperature is the parameter beingmeasured (suppose the temperature range is _15 0 F to 1100F) then a base station displayof 000.0 would correspond to _15 0F, and a display of 100.0 would correspond to 1100F;readings in between would be determined from the transducer calibration curve.Remote stations are called up by a two-tone sequential code (address) transmittedfrom the base station. A remote station address is selected by depressing onetone button in each of the two rows of ten buttons located on the front panel. Thestation is then called by pressing the front panel CALL button. Up to 100 stationscan be called from the base station.A microphone is included with the base station, permitting voice communicationwith the remote data stations.Operational specifications include:Environmental-operating temperatureElectrical-power600F to 1100F (Base station)-200F to 125 0 F (Remote station)117 VAC/60 Hz (Base station)15V Battery (Remote station)

""0>I r---------------~"'·:~~---------------~----, I'I Re"mbte electronics package I. I IPowermoduleiI Receiver ' ~ ~ransmitter I I'-IIIIAddress. decoder '. . SWltch 11 I,r- II 1L ..,. __ , "End.-of-messog€ .1SensorsI •IITransduceI:sInterfacemod,uler- II ~ !control logia I lr-s-tē.p-p"'-i-ng-- II generator II 11 II , Voltage I II . Controlled I 1Oscillotor " IIL_~ ~I ',. II I I Permeobility 1 "r

EXAMPLES OF TRANSMISSION SYSTEMS 29This system has proved to be highly reliable through three seasons of opera- .tion under very adverse conditions of rain, snow and sub-zero weather. Very littlemaintenance has been required other than the usual preventive and annual maintenancevisits. .Battery operation at remote stations has been more than satisfactory. ·The·stations have operated for periods of up to a year without battery replacement. Thisis true in spite of hourly interrogation during pro19nge~ r~iny periods. Normaloperation calls for daily call-up shifting to hourly during critical storm periods.Double mass plots comparing the Hy-Tel catch with nearby:gauges has shownvery close correlation throughout the season.Radio reliability has been outstanding. The only problems have been at~hose sit:s where the ra~io path is marginal, and these could be improved by the,nstallat,on of a mounta,n-top relay assuring a clear path from sensor site to basestation.. The Hy-Tel 9ystem has the advantages of low initial cost as well as lowmalntenan~e cost. In ar~as where no AC power is available, its ability to operateon battenes for long penods unattended is· a definite advantage.In the western United States, during the past several years, a large numberof telemetered hydrological networks have been established. This is due mainly tothe large number of agencies engaged in water management that require hydrological andmeteorological data from remote areas, In the State of California alone there arethirty-six such data collection networks operated by use of either radio or telephonecall-up.A major development currently in the planning and procurement stage is theuse of a synchronous orbiting satellite as a reloy for hydrological and meteorologicaldata.A multi-year (1967-69) test using the ATS I satellite has proved the feasibilityof such a system to - telemeter· streamgauge and precipitation data. Three..stations in California, Oregon and Arkansas were used. Data were relayed through t\~faxed satellite to the readout at Mohave, California.The new system using the GOES satellite will interrogate a network of streamand precipitation gauges in the western U.S. The reports will then be relayed, fromthe data collection platforms to the National Weather Service River Forecast Centers.It is possible, using such a satellite relay system, that the lorge numberof independent data collection networks could be consolidated into one. Data callupcould be programmed by computer and transmitted by land lines to the individualuser.

30 AUTOMATIC HYDROLOGICAL OBSERVATIONS3.3 Example III (U.S.S.R.). Automatic hydrological recording station (AHRS)The automatic hydrological recording station developed in the U.S.S.R. is intendedto perform routine observations at hydrological stationB when systematic storageof observed data is required for a given period (not less thon a month) and whenthe data has 'to be presented in a form suitable for further processing by electroniccomputers for hydrologicaf;1:ud'ies.AHRS consists ofa standard tape puncher.The information from eacho digital impulse code.Sensorsa sensor unit and an automation unit which has a memory andThere are ten sensors for measuring hydrological elements,sensor is transmitted to the automation unit in the form ofThe first two sensors measure woter-level and temperature. A hydrostoticwater-level gauge is used as a water-level sensor. Its operation is based on transducinghydrostatic water pressure into a mercury column movement in a manometer. Thechange in the mercury column is, in its turn, transformed into a digital impulse code.With some modifications, the instrument can measure water~levels from 0 to 3, 6, 9,or 12 metres.An automatic temperature gauge consisting of a thermometer with a platinumresistor is used as a temperature sensor. Measured temperature is transformed intoa digital impulse code. The device allows water temperature measurements within therange from 0 to +40 0 C.The automation unitThe automation unit is designed for automatic'datahydrological sensors according to the prearranged programme.gramming device, an information coding and storage device, aFigure 3.2). 'storage supplied byIt consists of 0 promemoryand a feeder (seeThe programming device is a combination of circuits controlling successiveprogrommed operotions of the whole system. In it signals of time are coded into abinary decimal code to be punched on a paper tape. The device consists of a masterclock (1), timing generator (2), intermediate frequency divider (3) and time-keeper(4).The e device consists of input devices (50 9depending on electronic counters (6 09)' storage -,(7), digital formation check circuit (8), intermediate storage - (9), matching'device (10), sensor of operational combinations (11), a sensor number dialling set(12) and a control device (13).The memory (14) stores the information during the unattended period. Atape puncher serves os a memory and a standard paper tape, 17.5 mm wide, is used asthe information carrier.

EXAMPLES OF TRANSMISSION SYSTEMS 31The feeder (15) guarantees power supply by alternate current circuit and byaccumulators.......--50 oQ :II8 I ---I r ..... -r--, r--, 1-/0 1'1--I 5, t--~ 6, t- _.J 9 ~L.__-' Ll._.1-- '"-7r--, r-'..r:--'", ---I 5 a 1---1 6 8 I-L..__J L __Jl-L .....I I I 6 I I /2 I I 11 II 5u I I 9 I II15 I I 13 IfI II I .-3 I l /,21Figure 3.2 - Block diagram of the AHRS automotion unitAHRS specificatians.---.~ _.- - - - - -(i) The AHRS system permits the automotic recording of 10 hydrologicol parameterssupplied by the sensors.(ii) The information is supplied to the automation unit: by all sensors simultaneouslyin a digital impulse code.(iii)The time and measurements are recorded on a punched tape in a binary decimalcode.

32 AUTOMATIC HYDROLOGICAL OBSERVATIONS(iv)(v)(vi)(vii)(viii)(ix)(x)The whole measurement cycle is 5 minutes.The measurement frequency may be varied by an aperatar and may be performedon-an hourly, two-hourly, or once or twice a day basis.The accuracy· of measurements:Water-level ± (1-2) cm.Water temperature t0.2°C.from the auto­Hydrological sensors may be at a distance of up to 2 000 mmation unit.The automation unit operates satisfactorily at temperatures from _35 0 C to+35 0 C and an air humidity up to 98 per.·cent; the ·puncher at temperaturesfr~m 0 to 30 0 t and an air humidity up ~o 70 per cent.The dimensions and the weight of the automation unit are 850 x 500 x 400 mmand 95 kg, respectively.The AHRS automation unit is installed in a shelter for protection against_9t~ospher~c influences (rain, wind, etc.).3.4 Example IV (U.S.S.R.). Mudflow radio warner (MRW)IntroductionSudden temporary torrents appear in mountainous regions as a result ofheavy rain storms i snow melt and flushins from glacial, moraine-dammed lakes, causingmudflows which are a dangerous phenomenon inflicting heavy damage and casualties.Protection against mudflows has been a matter of great concern. Variousprecautions are taken for this purpose in the areas where mudflows are likely tooccur: mud dams and chutes are erected, special mud flow watch and warning servicesare established, etc.The mudflow radio warner is intended to warn, with on ample time margin, thepopulation and authorities of mountain and sub-mountain regions of the formation andpassage of a mudflow registered by special sensors installed .in. a mountain riverbasin. Besides that, the MRW provides for remote supervision of river water-level,and the sharp fluctuations which often indicate a mudflow formation. For thispurpose the mud flow warner contains two sensors, one for water-level and one for mudflow.The MRW is based on the principle of . a signal frequency selection. Aspecific audio frequency is assigned to each of the three elements under study (thefirst water-level, the second water-level and the mudflow). The audio frequencydiscriminated by appropriate devices turns on the warning system.The MRWsystem includes transmitting and receiving stations.A transmitting statian (the system usuallystations) is established in a mountain river basin,incorporates several broadcastingin tributDries and in major

EXAMPLES OF TRANSMISSION SYSTEMS 33channels in such a way as to ensure an ample time margin before the mud flow reachesthe site to be warned, and to provide for a reliable duplication of the system. Themud flow warner transmitting station operates automatically and needs na attendance,except for monthly preventive maintenance.A receiving station (centre), to which the information is supplied fromseveral transmitting stations, is located at a town where the mudflow watch service islocated. The main criterion for the lacations of MRW receiving stotians is a reliableradio communication with all the broadcasting stations at selected frequencies.Operotors should keep watch at the receiving station throughout the period when a mudflowmay be expected. The distance between the transmitting and receiving stationsmay be up to 50 km.The function of the MRW transmitting station is to transduce a mountain riverwater-level rise up to pr~determined marks and mud flow appearance at the site intoradio signals, and to send them by the communication line to the receiving station.A" block diagram of the MRW transmitting station is presented in Figure 3.3.1n5 7 ....-g2 ¥ 10l-S LJt t6 8"IIFigure 3.3 - Block diagram of the mudflow radio warner transmittingstation

34 AUTOMATIC HYDROLOGICAL OBSERVATIONSSignals from water-level sensors 1 and 2 and from that of mud flow 3 ore fedinto the automation" unit where they are transformed into audio frequenc~__ (F l; F 2; F 3)and are then fed into the radio transmitter'"which broodcasts" modulated ,frequency'signals corresponding to a certain water-level or mudflow.In the on-position, signals of water-level sensors 1 and 2' are broaacastperiodically (at 50 and 25 minute intervals respectively). A mud flow warning signalis generated continuously for an extended time (over 6 hours) during which a mud flowbreaks the section line equipment.A transmitting station of the mudflow radio warner consists of: section lineequipment, water-level and mud flow sensors, local wire communication line, automationunitt radio transmitter and antenna,. power unit.The section line equipment serves ,for the installation of theo mudflow river. The equipment secures the sensors ond protectsmechanical damage.MRW sensors inthem againstWater-level sensors (1,2) send signals when the river water 'reaches twopredetermined levels at the site of the transmitting station. A water-level sensoris a float suspended from a lever. When the water-level rises the lever turns andcloses (or opens) an electrical circuit, th~s sending a signal to the automation unitwhen a predetermined level is reached.Mudflaw sensors (3) send a signal when a mudflow" passes the site. Thesensitive element is a steel rope stretched across the river channel and housed in aprotective tube. One end of the rape is fixed to one of the banks, and the otheris connected to the sensor contact system. The rape may be tightened or broken bythe mud flow. In both cases, the contact system comes into action and an electricalsignal is fed into the automation unit.The local communication line connects the sensors of the MRWmation unit housed in a shelter some distance from the gauging site.with the auto-'The automation unit is intended to transform the signals of mudflow andwater-level sensors into audio frequency signals, modulating the transmission andbringing the broadcasting system into operation at regular intervals.The automation unit consists of:(a)(b)Control system unit (4) designed for commutation offeeding networks of the automation unit and the broadcastingsystem;Programming device (5) prescribing time intervalsbetween the generation of sound signals of water-leveland mud flow and duration of the signal transmissionwhile the sensors are switched on;

EXAMPLES OF TRANSMISSION SYSTEMS35(c)(d)(e)A set of oudio oscillotors (6) generoting simple oudiofrequency oscillatians;Time delay unit (7) intended to switch on the radiotransmitter high valtage within a period of delay of40 to 100 seconds beginning at the time af switchingon the mud flaw sensor;Electromechanical clack (8) which switches on the automationunit as programmed.The automation unit operates satisfactarily at temperatures from -10 to +55 0 Cand with relative air humidity of up to 100 per cent.Broadcasting equipment and radio communication lines secure reliable ~aqiocommunication between MRW transmitting and receiving stations during the whole dangerousmud flow period, at any time of the day. Partable ultra-short wave radio stations(9) are used as broadcasting units in the MRW system. Ta make the communicotion linelonger, power amplifiers (10) may be used.The pawer unit (11) af the MRWstorage batteries.transmission station consists of alkalineThe receiving station receives signals of water-level rise and mud flowappearance at the sites of transmitting stations and switches on audio and light warnings·which allow the determination of the character and the origin of the signal.The block-diagram of the MRW receiving station is given in Figure 3.4.The diagram shows that low frequency signals from the radio receiver (12) output arefed as an input to the receiving filter unit (13) where they pass through a specialband filter and are then amplified. The amplified signal controls the actuator ofthe filter unit which in turn switches on light and audio warnings.The mud flow radio warner receiving station comprises: a radio receiver (12),a receiving filter unit (13), a receiving section with light and audio warning systems(14), a sound generator unit (15), a power unit (16).The radio station and the receiving filter unit are located at the rece~v1ngsection which also serves as a circuit commutator between these units and that for thewarning system (14)8 The number of receiving sections at the receiving station correspondsto that of the broadcasting stations around the·' g~ven receiving stati.on.An vItra-short wave radio receiver is used as a radio·-·-receiving device (12) because itis less influenced by atmosphere and man-made interference. The sound generator unit(15) is intended to produce audio and light warnings of water-level and mud flow.

36 AUTOMATIC HYDROLOGICAL OBSERVATIONS.. 15'IIi 7 F, ~ 012 IJ 1'1I16Figure 3.4 - Block diagram of the mud flow radio warner receivingstationAs the MRW must transmit water-level and mud flow signals from a selected site,it is necessary to estimate horizontal water-level marks and mud flow sensor installationsand to determine normal, dangerous, critical and mud flow river discharge usinglong-term observational data.3.5 Example V (France). Tele-snaw gauge with moving horizontal beamThe principle of the tele-snow-gauge with moving··horizontal beam is themeasurement of the density of various layers of the snow cover by the attenuation of ahorizontal beam of radioactive radiation which moves continuously in a vertical planeduring the measurement.

EXAMPLES OF TRANSMISSION SYSTEMS 37and 3.6.The arrangements for carrying out such measurements are shown in Figures 3.5Height of~~lumns 6m'Watertighcollars0.50 m,Cou tejOweightRadioGeiger-~IOllecounter and500 V powersu 1'r-ray beamRadioactil1eitsFigure 3.5 - Diagram of tele-snaw-gauge with moving horizontal beamThe radioactive source and the Geiger-MUller counter are balanced by a CQunterweigh tan d are moved by a "step-by-step" motor which is magnetically stopped' withoutcontact. The speed is not constant, but proportional to the count speed of thecounter. The supply of current in pulses of the motor is controlled by an electronicd i vide r in such a way that 3 840 pulses on the Geiger-MUller counter correspondto a movement of 10 em. ' .For every 16 pulses on the Geiger-MUller counter, the motormakes a step of 1/48th of a turn and moves the radioactive source .and the Geiger­MUller counter through 1/24th of a em. Due to the inertia of these two latter andthe elasticity of the drive, the movement is practically continuous.

38 AUTOMATIC HYDROLOGICAL OBSERVATIONSPolGester tube'180 II( 100)Interval of snowPolyester tubeIII I••600m~GM counter effective len th 120)Screen PI;> 5mmPlastic boxSource Cs 137m ,r beam2 Pb hemispheresPlastic boxe.

_~_-- ,-IEXAMPLES OF TRANSMISSION SYSTEMS 39-~ - j:--- -~'.'-+ --+-,-, ,/'y--!1/ V I-. . .//• ~.' ,•~Cou•• •• -/ f- -c.­•ES.2.,.~ 047 - ./ -- ., ./~. ,S.. 0,2,iII• ., ., oS• •Snow density 9 cm- 3iFigure 3.7 - Calibration of snow-gauge with horizontal beam.Relationship between the time of measuring 3 840 pulses on theGeiger-MUller counter and the density of the snowThe radioactive source, Caesium 137, has an activity of 30 millicuries. Thehalf-life of this element is 34 years, instead of 5.5 years for Cobalt 60; the radia-'tion which is 0 little less penetroting than the radiation from Cobalt, results ingreater sensitivity.Compared with other automatic devices for measuring snow cover which have beentried for a number of years in various countries of the world~ (viz. fixed verticalradioactive snow-gauge, pressure pillow snow-gauge) the tele-snaw-gauge with movinghorizontal beam has the following advantages.(i)It gives not only the water equivalent, but also the thickness of the snowcover and the densities of the various layers;

)~-~40 AUTOMATIC HYDROLOGICAL OBSERVATIONS(ii) A radioactive source of low activity only is required (of the order of 30millcuries) which only emerges from the snow for a few seconds per day andfor about 10 em;(iii)There is no upper limit to the depth of snow which can be measured, otherthan that set by the height of the columns.Figure 3.8 shows the various stages of the snow cover during the winter of1967-68 from 1 November to 15 May on Lac Blanc, Alpe d'Huez, as observed by a telemeteringdevice at Grenoble. More than 200 tele-soundings were made. Only a partof them is shown in the figure.De,;....1'\>~ '\Depth , ~ KWater eq valent......;- ~/~+--- - -1'rt~ L_~ h) i'l ~!~ ~ ~ "- "- "- "- ~ "- "J "J ,"- .'\: .'\: '\:-~ ~:n~ lb •• " .,"cl ""d ~ N :'"• Jan -t1ry"- ._ . Ilfem er,,February • I Match. . , -. pitl-~ :~~[. ~:-_-t~Figure 3.8 - Telemetering of the snow cover obtained by snow-gaugewith horizontal beam at Lac Blanc (winter 1967-1968)The succession in time of profiles, enables the packing of the various layersto be followed. In particular, contrasts of density are seen ~to persist in somecases for several months. This provides important information on the transformationof the snow cover and the risk af avalanches.Thus the device provides complete information which may be of interest to allcategories of users, not only hydrologists but also foresters, the winter sports industryand technicians connected with snow clearance and avalanches.

EXAMPLES OF TRANSMISSION SYSTEMS 41Further models of this device ore at present in use or are being constructed;it is proposed to equip in turn about 20 typical sites, selected on the basis of conventionalmethods used for 15 to 20 years for measuring snow cover with snow-gauges.The device was patented infirm a licence to manufacture it.terested in the device and hopes toDecember 1968, and talks are going on to grant aThe Ministry of Natural Resources in Quebec is indevelopits use in Canada.A day-to-day knowledge by means of telemetering equipment of variations inreserves of snow as soon as they occur, would make it possible to reduce to a minimumthe delays in bringing up-to-date forecasts of the amounts of snow available for theproduction of hydro-electric power, and so make use of vast amounts of energy beforethe thaw in the last months of the winter.3.6 Example VI (Hungary). Hydra II automatic digital telemetering systemThe wireless telemetering system is capable of collecting information from upt9.32 stations (with 9. sensors at each station) located within distances.up to 50 km.The system can be operated either automatically, on thebosis of a cyclic timeprogramme,or manually. The information is recorded in decimal units on paper tape.Warning signals may be produced when selected critical levels or rates are attained orexceeded.Two systems are in operation and a comprehensive programme of their nationwideapplication has been prepared recently.A detailed description of the system, its construction, principles of operation,design and installation is given in WMO Publication No. 304, "Scientific papers,presented at the Technical Conference of Hydrological and Meteorological Services"(1970). Only the technical data of the system are given here.Object:routine collection, recording and evaluation of hydrometeorological data.Principle or operation:serial (time multiplex), inquiry, radial arrangement.Information:2 ond 3 decimal digit measured data.Cycle times: long cycle time can be selected arbitrarily for measurements to becarried out with lower frequency T minutes, short cycle time for the measurements tobe carried out with higher frequency t = I minutes.6Recording:recording equipment and on-line printer.Alarm system: light and sound alarm signalling, if the incoming information exceedsa limiting value which can be preset for the individual sensors, being either an instantaneousvalue or the difference in value between two consecutive measurements.

42 AUTOMATIC HYDROLOGICAL OBSERVATIONSCapacity: Total number of measuring stations, maximum 32. Number of se~sors permeasuring station; maximum 9. Total number of sensors depending on the selectedcycle time•.Collecting of information: by precipitation sensor,by water-level sensor, with D.C. pulse-train output;pulse-train or analogue signal output.with D.C. pulse-train output;by other sensors, with D.C.Data-transmission: by carrier frequency, frequency-modulated with double-sound producedon the basis of a D.C. pulse-train containing the information (by VHF carrierfrequency); frequencies of the pulse-trains, maximum Hz; frequencies of the doublesoundbetween 300-3 400 Hz; carrier frequency 136-174 MHz; duplex distance betweentransmitter and receiver frequencies, minimum 4.5 MHz.Electrical construction: semi-conductor, germanium diode and transistor circuits onprinted wiring type EDS 5 200 plug-in boards.Mechanical construction: at both the measuring centre and the individual measuringstations, 2 or 3 frames depending on the capacity, and depending on the radio-wavepropagation conditions, omni-directional or high-gain aerial an a 6, 12 or 24 m highmast.Power supply: at both the measuring centre and the individual measuring stations ­from supply units connected to 220 V mains, with a power consumption of 900 Wat thecentre and 350 Wat the measuring station at maximum capacity.Permissible ambient temperature: in the measuring centre between +5 0 C and +40 o C, atthe measuring station between _25 0 C and +55 0 C.Permissible vibration:transport with lorry by road.!e~h~i~a! ~a!a_o! !h: ~r:c~p~t~t~o~ ~e~s~rPrecipitation collector: a standard cylinder of 200 cm 2 surface area, 1 m aboveground level, and a measuring cylinder capable of storing 100 mm of precipitation.Resolution: 1 in 100;accuracy in a measuringthat is, it records the precipitation level to within 1 mmcylinder of 100 mm.Measurement starting signal (inquiry signal): voltage pulse from - 3 V to 0 V, amplitude-3 V; pulse width: in automatic mode 2.5ms~ in manual mode 150 m s-l; load0­bility: 1 positive unit load (p.u.l.).Measuring pulse-train: from square-wave pulses, the number of which is proportionalto the precipitation level measured. Amplitude -3 V, frequency 50 pulses 1 5- , waveratio 1 I 1, loadability +3 p.u.l. or -3.5 p.u.l.Stop signal: square-wave signal with amplitude -3 V, pulse-width 510 mbility 1 p.u.l. or -4 p.u.l.-15 , loado-

EXAMPLES OF TRANSMISSION SYSTEMS43Supply voltoge requirement: -15'V, -3 V, 0 V, +10 V.Power consumption during measurement:20 Wat -15 V0.5 Wat -3 V0.5 W at +10 Vat measuring intervals:9 Wat -15 V0.2 Wat -3 V0.4 W at +10 VPermissible temperature: between -25°C and +55 0 C.Permissible relative air humidity:between 30 per cent and 90 per cent.Detailed technical data of the water-level sensorWater gauge: electrode-series gauge covering the complete range of water-level fluctuation,ploced on 0 vertical wall or laid obliquely.Resolution: 1:256 or 1:512; that is, it records the woter-level to within 1 cm accuracyin 256 or 512 cm water-level fluctuation.Measurementtude - 3 V;loadabilitystarting signal (inquiry signal): voltage pulse from -3 V to 0 V; amplipulsewidth: in automatic mode 500 m s-l, in manual mode 150 m ,-I;1 p.u.1.Measuring pulse train:water-level; amplitude+3 p.u.1.square-wave pulses, the number of which is proportional to the-3 V, frequency 50 pulses ,-I, wave ratio 1 : 1, loadabilityStop signal: square-wave pulse with amplitude -3 V, pulse width 510 m s-l,bility +1 p.u~l •.loa d a-Supply voltage requirement: -15 V, -3 V, 0 V, +10 VPower consumption: during measurement, 20 Wat -15 V1.2 Wat -3 V2.5 at +10 Vat measuring intervals, 6 Wat -15 V1.2 Wat -3 V2.5 Wat +10 VPermissible temperature:between _25 0 C and +55 0 CPermissible relative air humidity:between 30 per cent and 90 per cent.

BIB L I °G RAP H Y1. WMO, 1970:Guide to hydrometeorological practices.WMO-No.168.TP.82.2.WHO, 1958:Oesign of hydrological networks, by M. A. Kohler. Technical NoteNo.25, WHO-No. 82.TP.32.3.WMO, 1971:Machine processing of hydrometearological data.No.115, WMO-No.275.Technical Note4.5.WMO, 1969:WMO, 1971:Hydrological network design - Needs, problems and approaches, byJ. C. Rodda et 01. WMO/IHO Report No. 12.Guide to meteorological instrument end observing practices.WMO - Na.8.6. WMO, 1966: Instruments and measurements in hydrometeorology.No.76, WMO-No.191.TP.97.Technical Note7. WMO, 1966:Measurement and estimation of evaporation and evapotranspiration.Technical Note No.83, WMO-No.201.TP.105.8. WMO, 1968:9. WMO, 1968:Radar measurement of precipitation for hydrological purposes,E. Kessler and K. E. Wilko WMO/IHO Report No.5.Satellite applications to snow hydrology, by R. W. Popham.WHO/IHO Report No.7.by10. WMO, 1971:The precipitation measurement paradox - The instrument accuracyproblem, by J. C. Rodda. WMO/IHO Report No. 16.11. WMO, 1969:Hydrological requirements for weather radar data, by AWMO/IHO Report No.9.F. Flanders.12. WMO, 1967: Automatic weather stations.TP.104.Technical Nate No.82, WMO-No.200.13. IAEA, 1970: Isotope hydrology 1970. IAEA, Vienna.14. lASH, 1965: WHO/lASH Symposium on the Oesign of Hydrological Networks, Quebec.lASH Pub. No.68.15. UN, 1960: Hydrologic networks and methods (WMO/ECAFE Sf

46AUTOMATIC HYDROLOGICAL OBSERVATIONS16.17.UN, 1962:WMO, 1971:Field methods and equipment used in hydrology ond hydrometeorology(WMOjECAFE Seminar 1961), Flood Control Series Report No. 22,Bangkok.Technical Conference of Hydrological and Meteorological Services,Geneva, 28 September - 6 October 1970. Scientific Papers.WHO-No.304.18.WHO, 1972:Casebook on hydrological network design practices.WMO-Na.324.

ANN E X 1QUESTIONNAIRE ON HYDROMETEOROLOGICAL INSTRUMENTS OF PROVEN RELIABILITYPurposeConsiderable information on some meteorological instruments (i.e., precipitation,radiation, ambient temperature) is available in variousWMO reports. The prese~tsurvey is being conducted to collect recommendations on instruments for hydrologicalpurposes for which there is little guidance available. The recommendationswill be consolidated in a report for use of Members and others in establishing networks.Instruments to be reportedResponses to questionnaires should be submitted only for those instrumentswhich have been tested and proven reliable under actual operational conditions andwhich measure the following hydrometeorological parameters:(i)Rainfall intensity;(ii) Snowpack water equivalent and density (not snowfall) ;~ii)(iv)Meteorological elem&nts at floating stations for energy balance or masstransfer estimates of evaporation;Soil moisture including moisture in frozen soils but excluding lysimeters;( v) River and lake stage;(vi) Discharge measurements (all methods including current meters, pitot tube,chemical, volumetric, etc.);(vii)(viii)Water temperature in streams and lakes;Suspended sediments.QuestionnaireA. Reporting organization, country and address

48AUTOMATIC HYDROLOGICAL OBSERVATIONSB.C.InstrumentType (descriptive name, parameter(s) measured, number of instruments ofthis type in operation, brief description), recording, non-recording, telemetering,(power requirements, portability (weight and dimensions), accuracyand/or sensivity evaluation, useful life expectancy.Operational experienceRoutine maintenance required, installation requirements, skills required(installation, maintenance, operation), data reduction requirements,teletransmission of data, environmental conditions experienced (with reliableperformance, with unsatisfactory performance).D.E.teletransmission and re­Basic instrument, other required equipment,ceiver installations.Bibliography

ANN E X 2LIST OF INSTRUMENTS OF PROVEN RELIABILITY AND INSTRUMENTS FORAUTOMATION OF HYDROLOGICAL OBSERVATIONSExplanatory informotion for the headings of the tablesReported instrumentsReporting countriesNumber in operationRecordingAnalogueDigitalTelemeteredCostBasicTelemeteringUseful life (years)- descriptive name of instrument as reported;in some instances no name or descriptivetitle were furnished;- country of origin of reply;- actual number in field at time of completionof questionnaire;the form of the recorded data output is indicatedas chart or print;form of recorded data output is indicated aspunched tape, magnetic tape, cards or optional;- indicates that the data were telemeteredj- cost of the basic instrument and requiredequipment for non-telemetering installation;- cost of the transmission and receiving installations;- useful life expectancy as reported for theenvironmental conditions experienced;

Reportedinstruments..., Recording Reported cost.~-~ V>~. s..Reporting Number ,s..",,,, '"4-", => '"~..,countries inAnaloguel Digital Basic Tele- "'>,"'~operation "'''' machine form metered.... E :::>w4-'" o1. PRECIPITATION1.1 Instruments of Proven Reliability1.1.1 Tilting BucketThe principle of this type of recording gauge is very simple. The rain is ledfrom a conventional collector to a light metal container, or bucket, dividedinto two compartments. This container is so balanced that when one compartmentholds a predetermined weight of water the container tilts allowing the compartmentto empty and the rain to fall into the other compartment. This tiltingprocess is repeated each time the predetermined sample has beerr collected. Thetilting of the bucket is counted electrically and recorded on a moving chart.The record thus consists of discontinuous steps, the distance between each steprepresenting the time taken for a small amount of rain to fall.Belfort United States 650 No Chart $350. n.a. * 15Jurg Joss and EvioTognini Switzerland 6 Yes Print 2 300SFr 2 OOOSFr 25Pluviograph Plumatic Norway n.r. No Punched tape n.r. n.a. n..r.Precis Me Coni que France 200 Yes Chart 2 500FFr 15 OOOFFr 20Precis Me Coni que Morocco 10 No Chart i: 100 n.a. 10R-208-A Tunisia n.r. No Chart 1 250 FFr n.a. n.r.Recording Raingauge Italy 1 700 No Chart L7D 000 n.a. 10Recording Raingauge Republic of Korea 2 No Chart $300. n.a. n.r.Weather MeasureP511E (Heated) United States 200 Yes Chart $940. n.r. n.r.1.1.2 Float TypeIn this type of instrument, the rain is led into a float chamber containing alight, hollow float; the vertical movement of the float as the level of thewater rises is recorded on a chart. By adjusting the dimensions of the receivingfunnel, float an9 float chamber, any desired scale value on the chartcan be obtained. To provide a record over a useful period (at least 24 hours isnormally required) the float chamber has either to be very large (in which case a** n.r. not reportedn.a. not applicable~~ ....n::c~o8 ....~rolDUl;; '"~ ....§i!Ul

ReportedinstrumentsReportingcountriesNumberin-0 Recording Reported costOJ~s..'"::> ..Analogue I Digital Basic Tele- .... '",s..",,,,~.....~~~~...,'" >,operation "" machine form metered "'->-E ::>compressed scale on the chart is obtained), or some automatic means has to beprovided for emptying the float chamber quickly when it becomes full, the penthen returning to the bottom of the chart.Autographic Raingauge Ghana 47 No Chart $350. n.a. n.r.DG-200 (TOG-200) Poland 280 Yes Chart 4 860 zl 15 000 zl 10Fuess 221 Uruguay 7 No Chart n.r. o.a. n.r.Hellmann Ecuador 33 No Chart $180. n.a. 15-20Greece 15 No Chart $150. n.a. 15Indonesia 17 No Chart $200. n.a. 10+Morocco 5 No Chart n.r. n.a. 10United States 2 No Chart $300. n.a. 10+Kent Malaysia 135 No Chart M$495/- n.a. 10Recording Raingauge Republic of Korea 24 No Chart $350. n.a. n.r.Self Recording Rain~zIntensity Meter Republic of Korea 4 No Chart $700. n.a. n.r. m >

ReportedinstrumentsIReportingcountries"2.~Recording Reported cost ~-V>Number os...",OJinAnalogue I~...,Digital Basic Tele-OJ OJoperation machine form meteredw4-4-OJ " '"~ s...'" V>~ >,I-E =>0.'"1.1.4 Electrical (Photo)Photo Electric SnowParticle Counter United States 10 No Magnetic tapeA photoelectric snow particle counter counts individual snow particles andmeasures their velocity. The essential components of· the counter are a lightsource which produces a narrow, high intensity beam and two light sensitivediodes which have fast response times.Printing Raingauge Federal Republicof Germany 1 No PrintPrecipitation is collected by means of a raingauge of Hellmann type andsplit into calibrated drops by means of a specially adapted pipe at theoutlet. The falling drops are counted by means of a light barrier. Inaddition the precipitation total is measured with a rocker the contactsof which are also counted with a light barrier.Snowfall Intensity United States 10 No ChartAn electric eye measures the attenuation of a light beam by snow crystalsfalling through the path of the beam. Output from photomultiplier isrecorded on calibrated strip chart.1.1.5 Rainfall Intensity RecordersThese usually utilize the relationship between the rate of flow of waterthrough a restricted orifice and the head of water producing the flow.Rain is led from a collector to a float chamber with a small orifice inits base; the water rises in the chamber until the head· of water producesa flow through the orifice equal to the rate of rainfall. Hence thelevel of the float indicates the rate of rainfall, though the scale isnot linear. The Jardi rate of rainfall recorder uses the same principlebut obtains a linear scale by arranging for the effective size of theorifice to increase as the float rises. The Belfort gauge directs theflow from the funnel between the electrodes of a capaciter. Changes incapacity are related to the rate of rainfall.n.r. n.a.DM 9 500 n.a.$700. n.a.n.r.n.r.10>IHn::t:

ReportedinstrumentsBelfort No. 6069Jardi.~Recording~-;;;-Reported cost~oS-",,,,~Reporting Number'-=> countries inAnalogue I Digital Basic Tele- ... ~...,"'>,'"V>~operation f-e: "'''' machine form metered =>United StatesHong Kong1004YesNoChartCharts1.1.6 TotalizerTotalizer or storage gauges are used to measure total precipitation for periodsfrom one month to one year in remote, sparsely inhabited areas. A collectorarea of 300 cm2 is acceptable for a totalizer gauge but collectors of 500 cm2area give better results. The capacity of the receiver is chosen according tothe amount of precipitation and the frequency of observations. The receiverusually has a cross-section several times that of the orifice..Totalisator MI 67 Norway n.r. No n.r. n.a. n.r.1. 1.7 Ground Level >These gauges are installed with the orifice of the gauge at or near ground :z :z1evel . The gauge is protected from splash-in by antisplash shields x'"surrounding the gauge.Ground Level Canada 16 No Chart $400. n.a. 5 '"Ground Level Netherlands 20 No Punched tape $550. n.a. 101.1.8 Non-Record i ngThe ordinary daily raingauge usually takes the form of a collector abovea funnel leading into a receiver. The area of the receiver may withadvantage be made to equal 0.1 of the area of the collector.8-inch United States 10 000 No $75. n.a. II$410.£2001.2 Others1.2.1 Weighing TypeSensitive Tele­Recording PreciritationGauge Israel 1 Yes Chart $250.A distant recording precipitation gauge which indicates the onset of rain bymeasuring the recording of the first tenth of a mm of rain, as well as extremen.r.n.a.w...$620. 5510'"

Reportedinstruments~.... ""intensities. It consists of a highly sensitive weighing precipitation gauge,which empties automatically when lD mm of rain-2DOcc have accumulated. Therecording is made by means of a "Rustrak" galvanometer recorder which stamps dotsat 2 second intervals on a waxed paper chart. .2 SNOW COVER2.1 Instruments of Proven Reliability2.1.1 Snow Tube (Water Equivalent)Snow tubes are used to obtain vertical samples of the snow cover in the formof cores. They consist of metallic or plastic tubes with a sharpened lowerend or with a toothed cutting head. The diameters of different types of tubesvary from 3.5 cm to 9 cm, the internal diameter of the cutter being slightlysmaller than that of the corresponding tube. Tubes may be calibrated formeasuring the depth of the snow and slots are sometimes provided so that thecore can be examined. The water equivalent of the snow core is usuallyobtained by weighing.Adirondack Type United States 50 NoGW-l (10 cm2) Poland 200 NoItalian Italy 50 NoMt. Rose Snow Sampler United States 700 NoSwedish Type Sweden 40 NoSwiss Type Switzerland 50 NoVoluminal Densimeter(200 cm2) Poland 200 No2.1.2 Snow PillowSnow pillows are designed to measure the snow water equivalent indirectly byweighin9 the snow that is deposited on them. The pillows may be made froma number of materials including butyl rubber, rubber fabric, neoprene,fibreglass and sheet metal. The pillow is essentially a flat fluid containerfilled with antifreeze. Pressure transducers, electronic converters, andmechanical float devices are used to translate snow load into usable formfor on-site recording and radio transmission..~~~.,., Recording Reported cost~'-'"Reporting Number ,,-(i)

RepDrtedinstrumentsIRecDrding RepDrted cost.~~~~RepDrting Number ""2~,,-,'-'",,,,'1-", :::s '"cDuntries in~+' Ana 1Dgue I Digital Basic Tele-

ReportedinstrumentsReportingcountriesNumberinoperationTl'"~+'~~AnalogueRecordingDigitalmachine formReported costBasic,s-",,,,Telemetered"'".... ..--.~'"~ s-","", o> '""'>,=> "'~'"3 SOIL MOISTURE3.1 Instruments of Proven Reliability3.1.1 Neutron ProbeThis method is based on the principle of measuring the slowing of neutrons emittedinto the soil from a fast-neutron source. The energy loss is much greater inneutron collisions with atoms of low atomic weight and is proportional to thenumber of such atoms present in the soil. Hydrogen, which is the principalelement of low atomic weight found in the soil, is largely contained in the moleculesof the water in the soil. The number of slow neutrons detected by a counter tubeafter emission of fast neutrons from a radioactive source tube is electronicallyindicated on a scaler and indicates the amount of water per unit volume of soil.Oanbridge/NEA Sweden 6 NoNIC-5 United States --- NoUnited States United States 2 NoWallingford United Kingdom 20 No3.1.2 Bouwer Double TubeMeasures the hydraulic conductivity ofBouwer Double Tube United Statessaturated soil above the water table.14 No26 500 OKR n.a.n.a.$3 500. n.a.t: 1 000 n.a.$300.n.a.8+10-205+n.a.>IH():c

ReportedinstrumentsItaly Telehydrometro­. graphKB-2KentLea TelytoneLea RotaryLea ZerolightLPU-10RPU-10Metra No. 511Munro lH 125NegnettiOttDrumAutographic Type XHorizontal Type XLomufType XType XR 16R 16R 16R20.6lX 43Richard TypeSimilar to OttSteven A-35Steven A-35 or similarStevens Type FSwitzerlandTelemark'"RecordingReported cost,"",, "-,~ .... .Analogue I Digital Basic Tele-:....... '"Reporting NumberOJ'"'"countri es inoperation "'''' machine form meteredItaly 40 Yes Chart L,2 50()(l)0 L, 5 500 II 00 n.r.Poland 30 No Chart 4 200 zl n.a. 10Malaysia 80 No Chart M$700/- n.a. 15United Kingdom 100 Yes Chart £ 750 n.r. 5+United Kingdom 50 No Chart £150 n.a. 10+United Kingdom 25 No £100 n.a. n.r.Poland 20 No Chart 13 300 zl n.a. 10Poland 20 No Chart 24 000 zl n.a. 10Czechoslovakia 10 No Print 16 OOOKcs n.a. n.r.United Kingdom 100 No Chart £150 n.a. 10+Uruguay 2 No Chart n.r. n.a. n.r.Ecuador 6 No $360. n.a. 8 mo .Z zUnited Kingdom 20 No Chart £ 150 n.a. 10fTIxGhana 13 No Chart N¢209. n.a. 10'"Tunisia 35 No Chart 1 000 D~l n.a. n.r.'Sweden 150 No Chart 1 600 SKR n.a. ·10+Sweden 150 No Chart 2 150 SKR n.a. 10+Morocco 15 No Chart 5000 DH n.a. 10Tunisia 5 No Chart 1 500 OM n.a. n.r.Sweden 12 No Punched tape. 4 000 SKR n.a. 10+Sweden 150 No Chart 2 300 SKR n.a. 10+Republic of Korea 12 No Chart n.r. n.a. n.r.Uruguay 3 No Chart n.r. n.a. n.r.Australia many No Chart n.r. n.a. 15Canada 1 250 No Chart $650. n.a. 15+Ecuador 83 No Chart $400. n.a. 20Iraq 10 No Chart 10 250/- n.a. 25Republic of Korea 23 No Chart $200. n.a. n.r.United States 6 000 No Chart $350. n.a. 10United States 4 No Chart $250. n.a. 10+Switzerland 30 No Chart 700 SFr n.a. 50United States 133 Yes $747. $100. 17l>01"

Reportedinstru~.entsVa1dajVRD-1Zub1igSeba Type DeltaIRecordingReported costReporting Number ,,-",0) '"countries inAnalogue I Digital Basic Te1e-CI.>CI.>operation machine form metered =>..... "many No Chartn.r. n.a.50 No Chart12 OOOFor n.a.100 No Chart1 800SFr n.a.60 No ChartUSSRHungarySwitzerlandColombiaw4-.~~~Tl V>~ '-4-0) => '"~..., V> CI.>>, _n.r.1050""

ReportedinstrumentsReportingcountriesw4-.~4.1.5 StaffA graduatedLocal Manufactured4.2 Othersstaff gauge installed in the stream.Iraq 200 No 10 1/- n.a. 54.2.1 Float TypeOtt Water StageRecorder United Kingdom 100 NoAnalogue to digital conversion by punches operating againstOutput is on computer compatib1e'5 channel paper tape.4.2.2 HydrostaticWater Stage Meter llS.S.R, many YesPaper tapecoded discs.5 DISCHARGE5.1 Instruments of Proven Reliability5.1.1 Rotating Element Current MeterThe velocity of flow at a point is usually measured by counting the number ofrevolutions of a current meter rotor during a short time period measured witha stop-watch. The current meter is suspended in the flow on a rod or on awire. Two types of current meter rotors are in general use: the cup type witha vertical shaft, and the propeller type with a horizontal shaft. Most typesuse a make-and-break wire contact to generate an electric pu1se'for indicatingthe revolutions of the rotor.Acoustic Model Mark VI MalaysiaAmsler 505.036GhanaCurrent Meter withSelectorFrance45350NoNoNo£368n.r.n.a.n.r.M$600/- n.a.£345 n.a.1 790 FFr n.a.n.r.n.r.1055 000h·~~T.I Recording Reported cost V>OJ ~, s-Number ,swOJ4-w => '"in~....,Analogue Digital Basic Te1e-w >,V>~operation ~~ machine form metered :::>:to­z,."x'"'" '0

Reportedinstrur.,cntsIRecording Reported costReporting Number ,s- """,OJcountries in~+> Analogue I Digital Basic TeleoperationOJ OJmachine form meteredI-EOJ,~R-70 Us'SR n.r. No n.r. n.a. n.r.Gr.-64(like GR-64 but manual)U.S.S.R. n.r. No n.r. n.a. n.r.Remote distance hydrometric installation, electric powerGR-55 USSR --- No n.r. n.a. n.r. e>-iGR-42 (Velocity and 0Direction) USSR. --- No n.r. n.a. n.r. 0GR-2l M USSR. --- No n.r. n.a. n.r. -iHGurleynCurrent Meter Iraq 80 No .ID 200/- n.a. 50 ::I:Mayor Mexico 2 No $4 500Mex n.a. n.r. i:l622 Uruguay 1 No n.r. n.a. n.r.'" 0622-H Ecuador 5 No $800. n.a. 5655 United States 120 No $365. n.a. n.r.HHydraulic Current Meter Switzerland 40 No 1 000 SFr n.a. 3 ~rHydrometrical Current0~leter Sweden 25 No 1 50DSKR n.a. 10+ OJV>Hydrometrical CurrentMeter Switzerland 40 No gOO S Fr n;a. 30 '" ~Ice Current Meter United States 200 No $136. n.a. 10 -iM-l Hungary 100 No 10 OOOHunHn.a. 10Neyrflux Current Meter 0France 50 No 660 FFr n.a. 1 OOOhr zOTTArkansas Uruguay 1 No n.r. n.a. n.r.Arkansas Ecuador 12 No n.r. n.a. 8Arkansas Morocco 100 No 3.000DH n.a. 2+Arkansas Syria 15 No n.r. n.a. n.r.Arkansas United Kingdom many NoAssorted Australia 4 No n.r. n.a. n.r.C 1 Tunisia 20 No 1 OOODM n.a. 3C 1 United Kingdom 40 No £ 130 n.a. 10+C 31 Tunisia 20 No 2 800DM n.a. 5C 31 Ghana 6 No 1!I¢1 055. n.a. 5C 31 Germany none No 1 800 OM n.a. 10OJ'" o8'"V>

ReportedinstrumentsF6UTe1eferic SK 310,002Ott-MinorPricePygmySma 11 Pri ceSmall PriceSmall PriceSlush-N-AllUniversal AmsterI.... '".~~s..'"=> Analogue I Digital Basic Te1e- .... '"." Recording ~~(lJReportingReported costNumber ,s..countries in OJ'"~....,operation I-E "'''' machine form "'»metered "'~Ecuador 12 NoTunisia 5 NoUnited Kingdom 10 NoSwitzerland 25 NoUnited States 1 600 NoUnited States 3 200 NoGhana 3 NoRepublic of Korea 20 NoCanada 200 NoMalaysia 26 No::>n.r. n.a. 65 000 OM n.a. n.r.£ 135 n.a. 15+800 S Fr n.a. 20$77. n.a. 10$91. n.a. 10n.r. n.a. 5n.r. n.a. n.r.$120. n.a. n.r.M$1300/- n.a. 155.1.2 Other Than Rotatin9 Element Current MeterAcoustic United States 40 YesThe acoustic flowmeter is an instrument system that utilizes the difference invelocity of propagation of sound in the upstream and downstream direction tomeasure the velocity of streamflow. The difference in travel time of theacoustic pulse in the upstream and downstream direction is related to thevelocity of streamflow and this relation can be derived mathematically.$60 000. $600-4000. 10Contraf1ux France 15 No 1500-4.000FFr n.a. 10Venturi type neck fitted inside a non-loaded circular pipe. The discharge is inrelationship with the level. The Contraf1ux is a sensor. Any recording devicemay be added to it.Critical - Depth United States 10 No Chart n.r. n.a. 50The critical-depth flumes, built in place, of reinforced concrete, have a broadentrance section approximately the size of the original channel section, a 4.6metre long contraction reach with warped sidewalls to force the flow throQghcritical depth, and a 6.1 metre straight reach. A bottom slope of 3 percentkeeps the flow accelerating throughout the length of the flume and eliminatesdeposition of the heavy sediment load in the flume. The head measurement ismade in the section where the flow is supercritical.>zz1TIXI\)C>o.....

R;Reportedinstruments~~T.I Recording Reported costReporting Number '"~,s..s.. '"=> '"countries in 4-"~+'"" Ana 1ogue Digital Basic Tele-" :>,operation "'~"" machine form metered..... E :::>Dye-Dilution United States --- NoA fluorescent dye is injected into the stream flow and discharge is determinedby the dilution of the concentration of the dye.$1 500.Deep Water Isotopic United States 1 No Print $15 000.Twelve scintillation detectors are arranged in a circle of 25 cm radius aroundthe tracer discharge opening. A small quantity of the 1131 is discharged intocurrent. The detector receiving the maximum count rate prints out count ratedensity curve from which travel time is determined. .Fluorometer United States 50 No $1 595.A filter fluorometer is an instrument which gives a relative measure of theintensity of light emitted by a sample containing a fluorescent substance;the intensity is proportional to the amount of fluorescent substance present.Maritza Ecuador 1 No n.r.Consists of a double-acting windlass for weights up to 50 kg and a maximumreach of 80 m. The windlass carries a traction and an electrical conductingsuspension cable. A clutch mechanism gives independent horizontal andvertical movement. The windlass is set up on the bank with a pillar and pulleyon the opposite bank; tackle and counters for controlling horizontal andvertical distances. Also carries electrical contacts for connecting to arevolution counter.Modified Parshall United States 1 NoParshall flume with expanded section cut off behind throat section. Made ofwelded aluminum. Measures discharge from 0.0002 to 0.14 m3 with up to 60%submergences. Not for permanent installation.Moving-Boat Equipment United States 20 NoSpecialized instrumentation consisting of a portable sonic sounder, a vane withindicator, a propeller-type current meter with its associated electronicequipment, and an easily manoeuvrable small boat with some modifications,$130.$3 305.n.a.n.a.n.a.n.a.n.a.n.a."4-.~10n.r.1010n.r.5IHn:l:

ReportedinstrumentsI,'"Reporting Number '".,scountriesin ~+',"'''' Analogue I Digital Basic Tele-"0 Recording Reported cost .operation I-E "'''' machine form metered '-provide the capability needed for making discharge measurements by the movingboatmethod. During a traverse of the boat across the stream, a sonic sounderrecords the geometry of the cross-section, and a continuously operating currentmeter senses the combined stream and boat velocities.Neyptic Crest Gauge France 100's No 300-1000FFr n.a.Expansion wi~hout l~t~ral contraction o~ the b?ttom of a stream flow, thus creatingsuch hYdr~ullc COndltl0nS that one obtalns a slngle relationship between the crestand the dlscharge. Made of steel or plastic that will not lose its shape.Portable Weir Norway 2 No $70. n.a.Aluminum plate with goo weir notch to which a canvas sheet is fastened with screws.The weir is equipped with glass fibre scales on each side of the notch for levellingpurposes and for observation of the stage in the pond behind the weir.Powered Traveller Australia 5 No $6 000.This equipment is used to conduct current meter gaugings on wide and fast runningstreams. All controls are located on the bank. Gauging can be conducted overspans of up to 610 m and depths of 30 m.Watercourse Flowmeter Finland 10 No FilmThe watercourse flowmeter VM-ll helps to chart effectively the directions andspeed of slow lake flows in the vast watercourse areas. The meter is used ingroups of several instruments in order to get simultaneous measuring results atvarious points and depths in the whole area to be charted. The meter measuresthe horizontal direction and speed of the flow. The results are registered byB-radiation on filmstrips.5.2 Others5.2.1 Rotating Element Current MeterBraystone United Kingdom 1 NoPropeller type current meter with plastic propeller of nearly neutral buoyancycarried on jewelled and plain low friction bearings. Signals generated by reedswitch in easily removable capsule. Suitable for use with wading rods or anyother form of suspension.n.a.15+n.r.10$300. n.a. n.r.£120 n.a. n.r.~~x...,0­w

...., ---. -,."- ... _.__.-Reportedinstrurr;entsIReportingcountriesNumberinoperation.~~-;:;-Recording Reported cost~~s-'s-OJ OJ4:-w " '"~..., OJ>,Analogue I Digital Basic Tele-OJ",machine form metered "'~I-E :::>w4-2::5.2.2 Dye DilutionMobile Lab for Oil uti onStreamgauging United Kingdom 1 No .to 5 976 n.a. 5-10Mobile laboratory equipped for flow-gauging by dilution techniques. Mainanalytical equipment consists of: an Atomic Absorption Spectrophotometer :I>c::Uni cam SP 90, a Techni con auto-analyses, a G. K. Turn Fl uorometer Mk III, and~two portable conductivity bridges. Parameters measured include most of thetracers commonly used in dilution gauging.~6 WATER TEMPERATURE6.1 Instruments of Proven Reliability t1l;;;06.1.1 Water Temperature a r-Water thermometers are either mechanical or electrical. They are designed 8Hfor "point-to-point" measurements or continuous measurements.§;:r-Aanderaa Trl Sweden 16 No Magnetic tape $2 060. n.a. 5 aA. Ott Thermometer Iraq 10 No ID 1/500 n.a. 20OJBath Y Thermograph Canada 4 No Chart $5 000. n.a. n.r. mDirect ReadingThermograph Italy 20 No Chart L120 000 n.a. 10HElectrical Thermometer Sweden 20 No 1 250 SKR n.a. 5 aTemperature Detector United States 1 No Chart $1 554. n.a. n.r-. zThermometer &Vessell Switzerland 50 No 55 S Fr n.a. n.r. '"Water Thermometer Pol and 274 No 540 zl n.a. n.r.Thermistor TemperatureIndicator United States 1 No $500. n.a. n.r.--iHn:I:'"""~

ReportedinstrumentsI .,., Recording • Reported costReporting Number

....II Recording Reported cost ~-~Reported Reporting' Numbers.. "',s..=> '"instruments countries in"-w"'''' Analogue I Digital Basic Tele-~ .... w>,operation "'''' machine form metered "' ~1-", :::>P-61 Canada 50 No $600. n.a. 5United States 39 No $625. n.a. 10P-63 canada 10 No $800. n.a. 5P-67 Canada 6 No $600. n.a. 5PIHM L Batimeter Poland 100 No 1 200 zl n.a. 5Point Integrating Ghana 4 No n.r. n.a. 10 >Proportional Sampler United States 5 - 10 No Analysis $1 000. n.a. n.r.ẹ ...Silt Sampler France 200 No 5 250 FFr n.a. 20 ~Turbidisonde M226 0/10 Swi tzer1 and 20 No 350 S Fr n.a. 10 > ....7.1.2 Photo::J:This photo type measures the light absorption over a fi~ed path or .easures Clthe amount.Optical System United States 3 No $4 500. n.a. n.r.Sigrist Photometer UP2 Sweden 21 No 900 SKR n.a. 5-10 nSigrist Photometer UP51 Sweden 21 >No 11 000 SKR n.a. 5-10 rType FP/PH Canada 2 No Chart $1 000. n.a. n.r. 0 OJU>8 MULTIPLE PARAMETERS SYSTEMS8.1 Instruments of Proven Reliability8.1. 1 MeteorologicalPackage Canada 10 No Magnetic tape $10 DOD. n.a. n.r.The Met. Pack is a buoy mounting system of up to eight modular sensors(cammon types adapted for buoy operation) and a self-contained digitalmagnetic tape recorder, which has been developed for studies of airlakeinteraction on the Great Lakes. Averaged or filtered readings areautomatically recorded at 10 minute intervals for periods of up to 40days.8.1.2 Rimco/Sumner MRII Australia 80 No Chart $800.Aus n.a. 15An electro-mechanical chart recorder, self contained. battery powered.suitable for use with an assortment of transducers.w"-.~'"Hn'"rg0H'" j;;....H0:zU>.. -~- ...•.• ...•.,.

ReportedinstrumentsIRecording Reported cost.~~~IJ~Reporting Number ,,-'- '"GJGJ4-OJcountries inAnalogue I Digital Basic I Tele-'" '"~+'OJ>,OJ OJoperation machine form metered "'-f-E =>8.1.3 Sareg AutomaticAnswering Device France 300 Yes Magnetic tape 15 OOOFFr n.a. 15+Contains a magnetic tape on which are pre-recorded the numerical values of themeasured parameter. A set of magnetic heads permits the replay and transmission ofa spoken recording which gives the measured values of the parameters. Theinstrument is connected to a telephone network and may be called from anywherelike any ordinary subscriber.8.1.4 Schneider Monitor United States 6 Yes Punch tape $6 ODD. $1 650. 15Automatic dialling to monitor-receive on magnetic tape-electronically reduce todigitalized to punch tape with Flexiwriter for printout - punch tape to computerfor analysis.8.1.5 Servo-Programmer United States 180 Yes Punch tape $500. $600-$4.000. 5The servo-programmer, when used in conjunction with the analogue-to-digitalrecorder, has the capability to sequentially record on paper tape thevalues of electrical resistance from as many as seven individual probes.Power requirements are low and the instrument is designed to operate inremote locations on dry batteries.8.1.6 Water QualityMonitor United States 120 Yes . Punch tapeThis a modular system consisting of a digital recorder, timer, flow-throughsensor module, potentiometric-type sensors, submersible pump, and aprogrammed servo-drive unit. The programmed serVO-drive unit is designedto accept a maximum of 10 separate channels of input from the sensors and toautomatically program these inputs into the digital recorder. It consists ofa measuring circuit for each channel, a programmer, a solid-state amplifier,and a drive unit. A variety of sensors are commercially available for usewith the modular-type of water quality monitor.w4-$4 500. $600-$4 DOD. 58.1.7 Hy-Tel United States 25 Yes Print Magnetic tape $5 220. $8 000.­$45 570.Hy-Tel is a complete system. Each remote system can telemeter up to 22 differentsensors. Data information is transmitted by a FM-FM telemetry system to a base:»­z",x'"'""

00­coReportedinstrur.;entsI.~~~"0 RecordingReported cost~~.OJs-Reporting Number ,s-4-w '"Analogue1'"countries in -+' "" Digital Basic Tele- W>,Ww ~-operation machine form metered..... 2 ::>W4-station. Each base station can accommodate up to 90 remote stations. Developedsensors include total precipitation gauge, wind speed and direction, water stageand temperature.8.2 OTHERS8.2.1 Automatic Digital TelemeteringSystem HYDRA II Hungary 2 YesThe wireless telemetering system is designed for automatic hydrological datacollection in a region with radius of 50 km· (31 miles). The system consistsof a measuring centre and measuring stations. It is capable of collectingprecipitation height and water-level information from max. 32 stations, eachone is able to receive information from 9 sensors of the wishedhydrometeorological elements.8.2.2 Automatic HydrometricStation Romania 2 YesLevels of free water. surfaces, with the prospect of adding other elementssuch as: liquid precipitation, water and air temperature, thickness ofice, wind direction and speed. The measured values are converted byelectro-mechanical means to impulses, coded in accordance with a predeterminedcode.8.2.3 Epsylon WeatherWatcher EDL 12 Australia 0 No Magnetic tapeClimatological recording station including the following sensors: solarradiation, net radiation (optional), air temperature, wet-bulb depression,cumulative rainfall, wind run 2 m and wind direction (optional).n.r.n.r.n.r.n.r.$6 OOO.Aus n.a.8.2.4 Long PeriodDigital RecordersEpsylon EDL 10/2,EDL 10/4 Australia 1 No Magnetic tape $800.AusHermetically sealed, magnetic tape cassette loaded, battery operated recorder.Records events from external sensors against internally generated time events.Arange of sensors is available.n.a.5-10n.r.10-1510-15»~Hn:I:~§~55V> ,.";; '"-IH~V>

• ReportedinstrumentsReporting Number I'"'-GJGJcountries ina> a>operation"""Recording Reported cost.~~~w4--~. '- '"4-a> '" '"Analogue I Digital 8asic Tele-"'~machine form metered~ +-' GJ>,.... '":::>8.2.5 Long PeriodRecgrder (RIMCO/CSIRO) Australia 40 No Punch tapeElectro-mechanical battery operated recorder with solar cell recharge,hermetically sealed case. Records events from external sensors againstinternally generated time events (6 minute intervals). A range of sensorsis available.8.2.6 Normalair--GarrettAutomatic WeatherStatiop Oata 10-23 Australia 0 No Magnetic tapeThe NGL Automatic Weather Station is supplied as a self-contained package andcomprises all equipment necessary for automatically measuring and recordingrainfall, run-of-wind, solar radiation, wet and dry temperatures and hencehumidity (other climatological and water quality transducers may be added asrequired, up to a total of 12 input channels). The recording facilities arebattery powered and recordings are made on magnetic tape which allows for amaximum of 40 days uninterrupted operation.8.2.7 Plessey ClimateRecording Station MM2 United Kingdom 18 No Magnetic tapeClimatological record;ng station including the following six sensors: windspeed, wind direction, air temperature, humidity, rainfall, and solar radiation.$2 OOO.Aus n.a. 10-15n.r. n.a. n.r.£ 1 500 n.a. 7-108.2.8 Plessey HydrometeorologicalStations Event Recorder Australia o Yes Magnetic tape $6 OOO.Aus n.r. n.r.> zZmx'"$

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