Conceptualization of Rain Water Harvesting Structures in Delhi, India

Rain water harvesting has become imperative and included in States ’ byelaws to use the non-committed monsoon runoff to supplement the available water resources and increase the sustainability of aquifers. Delhi has a total demand of 4.0 MCM per day for a population of 1.5 million but the total availability from surface and ground water resources is less than 3.6 MCM per day. It is estimated that 65.6 MCM is available for artificial recharge which can be harvested by constructing different types of recharge structures like check dams and combination of pit/trench with recharge wells. On the basis of geomorphology and drainage, five distinct artificial recharge environments have been classified, they are:1-Development and recharging of 97 sq Km of Yamuna flood plain having utilizable potential of 78 MCM up to 4m depth; 2-Roof top rain water harvesting for effective recharge of 6 MCM per year;3-Ridge area, of 145 sq km has a runoff potential of 6.79 MCM for recharge each year;4-Surplus of canal water during monsoon having storage potential of 40 MCM for recharging depleted aquifers; 5-Surplus of Najafgarh drain estimated as 58 MCM for recharge of depleted aquifers in West Delhi. The cost of roof top water harvesting structures is between Rs. 1.60 to Rs. 7.0 per m3. The impact assessment of 7 roof top schemes show recharge of 5000 m3 and 8 roof top and pavement schemes show 8500-20000 m3 of recharge in a year