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RAIN WATER HARVESTING. RAIN WATER HARVESTING. Rain water harvesting is collection of rain water through Storage for direct use (2) Recharging of ground water. WATER CYCLE. A FEW FACTS. Only 3% of water is available for human use. Only 1% of water is in lakes and rivers.
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RAIN WATER HARVESTING • Rain water harvesting is collection of rain water through • Storage for direct use (2) Recharging of ground water.
A FEW FACTS • Only 3% of water is available for human use. • Only 1% of water is in lakes and rivers. • Only 10% rain water is harvested currently. • On an average rains, occur only for about 100 hours.
WHY RAINWATER HARVESTING ? • Surface water is inadequate to meet increasing demand. • Decreasing level of Ground Water due to excessive pumping (hence need to recharge). • Uneven distribution of rainfall . • Reduced infiltration area.
DECLINE IN GROUND WATER LEVELS • In Delhi the water level in 1960 was, by and large,within 4 to 5 m but by 2001 it has gone down by 2-6 m in alluvial areas, 8-20 in south west district and 8-30 in south district.
RAIN WATER HARVESTING PRACTICES IN INDIA • LAKES/TANKS • Most of the old cities, which were not on river banks, had huge lakes/tanks to store water. • Either these have been lost or their capacity greatly reduced due to silting. • TANKA • Small underground tanks in houses/temples/ dharamshalas • Popular in Bikaner, Dwarka • BAOLI/BAVADI • Traditional stepped wells in Rajasthan and other states of northern India.
RAIN WATER HARVESTING PRACTICES IN INDIA • KHADINS (DHORA): • Long earthen embankment built across the lower hill slopes lying below uplands • Popular in Jaisalmer, Western Rajasthan • BHANDARAS • Check dams / diversion weir used to impound water. • Raise water levels in rivers. • Popular in Maharashtra. • JOHAD • Small earthen check-dam which capture and conserve water
RAIN WATER HARVESTING PRACTICES IN INDIA • KERE • Tanks fed by channels branching off from check dams. Out flow of one tank supplied water to another tank. (Popular in Central Karnataka) • ZINGS • Small tanks found in Ladakh which collected melted glacier water. • KUL • Water channels in mountains to take water from glaciers to villages.
FROM WHERE TO HARVEST RAIN • Roof Tops • Paved and Unpaved Areas • Storm Water Drains • Water Bodies • Water Streams
RAIN WATER HARVESTING IN BUILT UP AREAS • Roof top Rainwater harvesting can be used for storage or recharge • If for storage : (1) Water from first major rain to be flushed off; (2) Filter to be used • Arrangement of gutter, down take pipes, surface drains to be adequate to carry rain water.
ASSESSMENT OF RUN OFF • Run off = Catchment Area x Run off Coefficient x Rainfall • Run off Coefficient depends on the catchment characteristics : • Roof Top 0.75 – 0.95 • Paved Area 0.50 – 0.80 • Bare Ground 0.10 – 0.20 • Green Area 0.05 – 0.10
SELECTION AND DESIGN OF RECHARGE STRUCTURE • Harvesting potential • Rainfall quantity and pattern • Requirement pattern • Sub surface geological features • Aquifer depth • Strata and presence of impervious layer
RECHARGE PIT • Used to recharge shallow aquifers • Width : 1-2 m • Depth : 2-3 m • Pit filled with boulders (5 – 20 cm), gravels (5-10mm) and coarse sand ( 1.5 – 2 mm) • If any clay layer is encountered it should be punctured with auger hole.
RECHARGE TRENCH • Used to recharge shallow aquifers • Width : 0.5 m to 1.0 m • Depth : 1.0 m to 1.5 m • Length : 10 m to 20 m • Back filled with filter material • Auger Holes to be made to puncture clay layers if any.
RECHARGE TROUGHS • Located at entrance of complex to drain out run off from the compound residential/institutional buildings. • Similar to Recharge trenches except • Bore holes are drilled at regular intervals
ABANDONEDDUG WELLS • Abandoned dug wells can be used as recharge structures after de-silting and cleaning. • Run off should pass through desilting chamber.
ABANDONED TUBEWELL • Can be used for recharging shallow or deep aquifers • Water should pass through filter media • Tube well should be redeveloped before use as recharge structure
ABANDONED HAND PUMPS • Abandoned hand pumps can be used to recharge shallow aquifers. • A filter chamber is provided to arrest impurities.
INJECTION WELL • Required if impervious layer lying above aquifer • Bore Hole of 20cm dia drilled upto 2 to 3 m below water table • Sometimes slotted casing pipe is also inserted • Gravel filled up in the bore hole around casing pipe • Filter mechanism is provided at top
RECHARGE WELLS • Used to recharge deeper aquifers • Diameter : 1m to 5m • Depth : 2m to 20m • Water may be passed through filter media to avoid choking of recharge wells
VERTICAL RECHARGE SHAFTS • Used for recharging shallow aquifers which are located below clayey layers at depth of 10 m to 15 m • Diameter : 0.5 m to 3 m • Depth: 10 m to 15 m • Back filled with boulders gravel and coarse sand • In top 1m-2m depth, brick masonry work is carried out for stability of structure.
SHAFT WITH RECHARGE BOREWELL • Used if aquifer is available at greater depth (20 m to 30 m) • A shallow shaft of 2 m to 5 m diameter and 5 m to 6 m depth with recharge wells of 10cm to 30cm dia to recharge water to deeper aquifer • Filter media at bottom of shaft.
RECHARGE STRUCTURE Recharge Pit Recharge Trench Recharge through Hand Pump Recharge through Dug well Recharge well Recharge shaft Lateral shaft with bore well Shaft per m Bore well COST (RS.) 2500-5000 5000-10000 1500-2500 5000-8000 50000-80000 60000-85000 2000-3000 25000-35000 APPROXIMATE COST OF RECHARGE STRUCTURE
RAIN WATER HARVESTING IN RURAL AREAS Two categories of methods • Percolation Methods : These aim at increasing percolation by • Preventing run off • Increasing water contact area • Increasing water contact time • Providing passage through impervious layers • Regulating run off to continue it much after the rains • Storage Methods : Water is stored in different kinds of structures.
MAINTENANCE OF RWH ARRANGEMENT • Use Flushing Device in beginning of each rain (in case of storage arrangement). • At the end of dry season clear debris from catchments, check gutter, supports and pipeline connections. Repair if required. • Gutters, screening etc. should be cleaned at the end of dry season and periodically during rainy season. • Filters should be cleaned periodically. • The recharge structures should be declogged and cleaned to maintain infiltration rate.
BENEFITS FROM RAIN WATER HARVESTING • Mitigates water scarcity • Balances natural water cycle • Improvement in quality of ground water • Saving in energy bill • Arresting ingress of saline water in coastal areas • Reduced runoff avoids chocking of storm water drains and water-logging • Reduced soil erosion
NEED OF THE DAY : A HOLISTIC APPROACH • Afforestation • Rain Water Harvesting • Efficient Means of Irrigation • Crop Diversification • Conservation of Water • Recycling of Water
SOCIO LEGAL ISSUES • Awareness • Individual Benefit v/s Social Benefit • Why would individual/developer spend for RWH if no direct benefit ? • Hence needs for incentive and/or prohibitive measures • Water Policy • Principal of treating water as free commodity to be abandoned • Realistic Pricing (Incentive for saving, progressive tariff) • Legislation to make RWH arrangement a must for buildings, with incentive in water charge structure • Charge for diverting runoff to community drainage ?
LEGISLATION ON RAIN WATER HARVESTING • New Delhi • MOUA has made RWH mandatory since June 2001 if roof area≥100sqm or plot area≥1000sqm • CGWA has made RWH mandatory in all institutions and residential colonies in notified areas. • Mumbai: RWH mandatory since Oct 2002 for new buildings with area≥1000 sqm • Chennai:RWH has been made mandatory in all new buildings of three or more storeys.
LEGISLATION ON RAIN WATER HARVESTING • Hyderabad: RWH made mandatory since June 2001 if area ≥300 sqm • Kanpur: RWH made mandatory for new buildings with area ≥1000 sqm • Indore: • RWH made mandatory for new buildings if area≥250 sqm • Rebate of 6% in property tax as incentive for RWH
LEGISLATION ON RAIN WATER HARVESTING • Rajasthan: RWH made mandatory for new buildings in urban areas if plot area≥500 sqm • Haryana: • HUDA has made RWH mandatory for new buildings in urban areas irrespective of area • CGWA has asked all institutions and residential buildings in notified areas of Gurgaon and adjacent industrial areas to go for RWH
LET US CONTRIBUTE OUR MITE AND ATTEMPT TO RESTORE WATER CYCLE THANK YOU