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RAIN WATER HARVESTING
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RAIN WATER HARVESTING
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RAIN WATER HARVESTING
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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.
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WATER CYCLE
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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.
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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.
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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.
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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.
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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
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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.
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FROM WHERE TO HARVEST RAIN • Roof Tops • Paved and Unpaved Areas • Storm Water Drains • Water Bodies • Water Streams
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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.
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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
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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
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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.
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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.
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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
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ABANDONEDDUG WELLS • Abandoned dug wells can be used as recharge structures after de-silting and cleaning. • Run off should pass through desilting chamber.
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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
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ABANDONED HAND PUMPS • Abandoned hand pumps can be used to recharge shallow aquifers. • A filter chamber is provided to arrest impurities.
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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
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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
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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.
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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.
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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
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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.
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LAGOON DURING RAINS
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CHECK DAMS
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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.
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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
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NEED OF THE DAY : A HOLISTIC APPROACH • Afforestation • Rain Water Harvesting • Efficient Means of Irrigation • Crop Diversification • Conservation of Water • Recycling of Water
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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 ?
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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.
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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
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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
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LET US CONTRIBUTE OUR MITE AND ATTEMPT TO RESTORE WATER CYCLE THANK YOU
Source: https://www.slideserve.com/nolson/rain-water-harvesting-powerpoint-ppt-presentation
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