Hydraulic ram pumps and Sling Pumps

H MISCELLANEOUS: DIXIT and PATILscheme for all their needs. Even the local sugar factory hadto make temporary arrangements to draw water for drinkingpurposes, as well as for construction, from the scheme.InferencesLooking back on 5 years in the State PHE Deptt., 2 yearson site and 3 years in the Circle Office, the author feelsproud of fellow engineers who trudge to rural areas andexecute work under conditions that are often far fromideal. Unfortunately, their efforts are seldom lauded asthey fail to supply water during times of crisis— a failurewhich results from improper and inadequate selection ofthe water source. The source must yield a minimumquantum of water during the dry season of May and June.Rain water harvestingThe collection and storage of rain from run-off areas suchas roofs and other surfaces has been practiced sinceancient times. It is particularly useful where water supplyis inadequate. If collection and storage are designedcarefully,it is possible for a family to live for a year in areaswith rainfall as little as 100mm per year. Several observationsmade in Zimbabwe, Botswana and Israel show thatbetween 80 to 85 per cent of all measurable rain can becollected and stored from outside catchment areas. Thisincludes light drizzle and dew condensation which occursin many parts of the country during the drier months.The run-off from a catchment area can be worked out bythe simple formula,Q = C x I x AWhere, Q = discharge in cu.m.C = co-efficient of run-offI = Total rainfall per annum, mA = Catchment area, sq.m.The co-efficient of run-off depends upon the shape,size, soil conditions, temperature, geological conditionsof the area of the catchment. However, on the basis ofaverage annual rainfall in the area the co-efficient an beassumed.Dry tracts with annual rainfall 350 to 750 mm – 15 to 20 per centIntermediate Zones rain 750 to 1500 mm – 20 to 30 per centHigher Zone with rainfall above 1500 mm – 30 to 55 per centRoof and paved areas80 to 90 per centAs an example, if the rainfall is 635 mm per year the runofffrom a suitable catchment area will be about 500 mm,and an area covering 1 hectare may yield 50,00,000 litresof water per year — enough for 500 heads of cattle for sixmonths. One millimeter of rain falling on one sq. m. of area willyield approximately one litre of water. The requirement forsolely domestic purposes may be 15 to 20 litres per headper day. For a family of of 5 persons, the daily requirementwould be 100 litres. If we assume that the longestperiod without rain would be 6 months, the volume ofwater required to last throughout the dry season wouldbe 180 x 10 = 18,000 litres.All harvester surfaces, being exposed to the atmospherethroughout the year, are subject to contaminationby dust, insects and birds. Harvester surfaces at groundlevel, however, can be fenced and kept clean. Storagetanks may be built below or above ground. The tanksshould be fully enclosed to prevent evaporation. Allapertures should be screened to prevent the access ofmosquitoes, rodents, lizards, etc. The first flush of thenew rains should be allowed to run waste. Sometimeswater is passed through a sand filter before it is consumedfor drinking.Artificial harvestersIf water is required where there is no roof or rockyoutcrop suitable for collection, the construction of animpervious surface can be undertaken on the grounditself. Reinforced concrete can be used to make the surface;chicken wire reinforcing should be used to preventcracking of the floor. An alternative technique is to lay alarge piece of plastic sheeting in a hollowed out andlevelled area of ground. A layer of sand is laid over thebottom of the excavated area and raked flat. The sheet ofplastic is laid out over the layer of sand and the edgesraised up against the side walls of the excavation.A drainage system is now laid in the form of a slottedPVC pipe which drains away in the reservoir used forstorage. Finally, a layer of gravel or very coarse washedriver sand is laid on the bed. The edges of the area shouldbe raised with a rim of concrete work. No part of theplastic sheet should be exposed to the sun or it will perishwithin a year. The area should be fenced off to preventaccess to animals. The construction of the reservoir is thecostliest. It may be either in stone masonry or R.C.C. andconstructed either below or above ground. (A detaileddesign of the scheme along with drawings of the artificialharvesters discussed are available with the authors).Cost of the projectDeveloping and maintaining harvesting area : 6750 sq.m.at Rs.20/- per sqm. = Rs. 135,000.Constructing masonry underground or above groundtank of size 15x12x1.8 = 324,000 litres at the rate of Rs.2/- per litre = Rs.648,000.Add 10 percent towards misc. = Rs.78,300Total Cost = Rs.861,300.Therefore cost per head = Rs.1725.Conclusions• The efforts of state and central agencies to provide anadequate water supply to rural people have failedmiserably due to non-availability of reliable sources ofwater. It is necessary to store water in lakes, ponds, andartificial ditches and improve the ground water table.• It is also necessary to prepare a national water gridand connect the rivers. All irrigation projects must betaken up for completion immediately. Projects likeTalagu Ganga Project and Narmada Project must becompleted in priority. Similar projects should be conceptualizedand implemented to overcome the problemsof drinking water in India.365