RAIN WATER HARVESTING (RWH)
WHAT IS RAIN WATER HARVESTING :
Rain Water Harvesting is the accumulating and storing of precipitation. It is used to provide water for
consumptive and nonconsumptive use.
WHY IS RAIN WATER HARVESTING NECESSARY :
There are two main reasons : a) Surface water is inadequate to meet our demand and we have
to depend on ground water. b) Due to rapid urbanization, infiltration of rain water into the subsoil has decreased drastically and recharging of ground water is diminished.
AVAILABLE CATCHMENTS FOR RAIN WATER COLLECTION :
Rain should be collected from roof top, road top and some specially prepared areas of ground.
Water collection from Roof Top
RAIN WATER HARVESTING TECHNIQUES :
There are two main techniques for RWH: a) Storage of rain water on surface for future use. b) Recharge to
ground.
STORAGE OF RAIN WATER :
It is a traditional technique. Underground tanks, Ponds, Check dams, Weirs are the structures used for rain water storage. It is used in rural areas where space is available for the construction of structure for water storage and where the annual variation in rainfall is less.
RECHARGE TO GROUND :
Recharge to ground water is a new concept of RWH. This technique is frequently adopted in urban areas where space is not available for the construction of structure for rain water storage. Pits, trenches, wells, shaft etc are constructed for ground water recharge.
FERRO CEMENT TANK :
It is used as a rain water storage structure. It is made from wire reinforced mixture of sand, cement and water. Some of its salient features are : a) It is strong, versatile, long lasting, low cost. b) It is light in weight, highly tensile and flexible than ordinary concrete structure. c) Low maintenance cost.
TRENCHES AND BOREWELL FOR GROUND WATER RECHARGE :
Bore well Trench
QUALITY OF RAIN WATER :
The physical as well as chemical quality of water Is important to decide its suitability for drinking purpose, cooking purpose etc. Various standards are formulated by many National and International agencies and all the standards are recommendatory. Rain water must be collected from projected site(s). The parameters
analyzed include ph, conductivity, total dissolved solids, hardness, Ca, Na, Mg etc.
BENEFITS OF RAIN WATER HARVESTING :
‡Improvement in infiltration and reduction in runoff. ‡ Improvement in groundwater levels and yields. ‡ Reduces strain on Special Village Panchayats/ Municipal / Municipal Corporation water supply. ‡ Improvement in groundwater quality. ‡ Estimated quantity of additional recharge from 100 sq. m. roof top area is 55.000 litres.
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