Rain Water Harvesting in Rural Area

Rain Water Harvesting in Rural Area

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  RAIN WATER HARVESTING IN RURAL AREA WATER MANAGEMENT FORUM The Institution of Engineers (India) http://www.wmf-iei.org/index.php/
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  What is RainWater Harvesting (RWH)? • Process of arresting and storing rain water for efficient application and conservation • An effective way of utilising large quantum of water which otherwise goes as surface runoff. • RWH has 2 components: 1) Rain water collection for storage 2) Recharging groundwater What is artificial recharge to ground water? • Process of enhancing ground water storage artificially at a rate exceeding natural rate of recharge • Possible by putting up small structure enabling storage and infiltration
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  What are theadvantages of RWH & recharge?  Improvement in ◦ ground water levels ◦ water availability in wells/ tube-wells ◦ the quality of ground water through dilution ◦ living conditions in rural areas  Saving energy in lifting ground water – one meter rise in level saves 0.40 KWH  Reduction in soil erosion due to reduced surface water runoff  Prevention of sea water ingress in coastal areas
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  Aspects to beconsidered for designing RWH system • Hydrogeology of the area including • nature & extent of aquifer, •soil cover, •topography, •depth to water level, • ground water quality • Availability of source i.e. surplus runoff • Hydro-meteorological characters – rainfall duration, pattern, intensity • Area contributing runoff like roof top area, etc
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  CATCH RAIN WHEREIT FALLS What are the Rain water Harvesting techniques for Rural areas? Recharge Shaft -- 2 meter diameter or more, ends in permeable strata - If unlined, backfilled with filter medium - If lined, small conductor pipe leads recharge water to • Useful for village ponds having top impermeable clay filter • Shaft top projects above bed-level of pond and is taken upto half the full water depth • Top one or two m done with brick masonry for stability of shaft • Half of water collected in pond recharges groundwater. The other half used for domestic purposes.
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  DUG WELLS •Abandoned andexisting dug wells can be put to use after removing silt • Periodic chlorination required • Recharge water taken through delivery pipe via silt chamber to well bottom to avoid scouring.
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  CHECKDAMS/NALA PLUGGING • Constructedacross streams with gentle slopes. • Should have sufficient thickness of permeable bed • Water confined within the bank of stream • Height not to exceed 1.5 to 2 meter in general • Excess water flows above wall • May be constructed with masonry/ concrete • Downstream water cushion chamber required to prevent scouring.
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  Underground Checkdam/ Subsurfacedyke • Constructed below ground to retard movement of water. • Site to have shallow impervious layer with wide valley, narrow outlet • One or two meter wide trench dug across streambed with depth extending to impervious layer. • Trench can be filled with clay or concrete wall upto 0.5 meter below ground level • PVC sheet of 3000 psi tearing strength at 400 to 600 gauge or LDPE film 200 gauge can also be used along excavated face of the trench
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  Percolation Tanks • Located on highly permeable soil so as to allow water stored above to percolate and effect recharge • Normal storage capacity 0.1 to 0.5 million cubic meter • Tanks created by earthen bund with masonry spillway  Built along hilly slopes Gully Plug across gullies/ small streams using locally available stones, clay etc.  Better selection where slope breaks so as to have some storage behind  Prevents soil erosion and conserves soil moisture
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  Contour Bunds • Suited for lands with moderate slopes without involving terracing • Suited for low rainfall area where runoff can be stored on slope all along contour of equal elevation. • Prevents soil erosion and conserves soil moisture • Spacing between two contour bunds depends upon slope and soil permeability.