RESERVOIR SEDIMENTATION ASSESSMENT GUIDELINE - Aneel

Reservoir Sedimentation Assessment Guideline• For all installed level references (RRNN), localization sketches shall be presentedwith all required data for its accurate characterization. Besides that, they must bedully referenced to in the survey maps.• Installation of ruler – Taking into consideration the long distances to be surveyed,and the need for the work to be referenced to the reservoir maximum normal level,the rulers to be installed must be positioned in a proper way, with level referencematerialized nearby it and fastened one to another, mainly altimetrically. During thesurvey, rulers must be read at short intervals - it may be hourly. The number oflimnimetric gaging stations will depend on the distance between the referencestations to be used for the survey.• For all those gaging stations, description cards on installation shall be presented.• Positioning – The positioning for each depth measured shall be satellite -based; it isrecommended to use the DGPS (Differential Global Positioning System). Thatsystem continuously registers the position of the vessel used, through a mobilereceiver and a reference station, located on a known point of the coordinate onground. That set works through data link, thus allowing the station based on groundto send data on positioning correction for the mobile station; therefore, a betteraccuracy is achieved for those coordinates obtained on board. The system shalloperate through the continuous positioning of measured depths, with accuracy of 2to 5,0m and ranging from 50 to 80km.There must be a PC coupled to the system, presenting a pre-established program forarea and lines to be surveyed, containing the space between lines, the direction ofprofiles and the interval between the points examined, according to the mesh. Itshall also allow for the repositioning of the vessel at any profile or position asrequired, being dully displayed at the computer screen.• Bathymetry – For the bathymetric survey, a good digital echobathymeter must beused, with a 208 kHz-transductor, or similar, capable of providing permanent anddetailed records on the bed high resolution topography for defining the watersedimentinterface, in such a way as to operate in very deep waters. Theechobathymeter must be daily calibrated, by the beginning and by the end of works,through suspended card process, for purposes of correcting sound velocity andprecisely defining depths.The echobathymeter shall be coupled to the mobile receiver and to the computerthrough a program that allows for the automated and simultaneous record of depths,as well as their positioning, in magnetic means (diskette) for further processing.If the water level is lower than the reference level, banks must be leveled - throughtopographic equipment or with GPS - up to the desired level.ANEEL – Brazilian Electricity Regulatory Agency / SIH – Hydrologic Studies and Information Department62