INTRODUCTION<br />The total amount of water on earth remains constant. The rapid growth in population together with the extension of irrigated agriculture and industrial development, are putting stress on the natural ecosystems. In the face of growing problems, society has begun to realize that it can no longer subscribe to a use and discard philosophy with any natural resource. One such resource is WATER. To deal with it, a technique called RAIN WATER HARVESTING was introduced where rain water is used to meet some of our daily needs. <br />
WHAT IS IT???<br />Rainwater harvesting is the accumulating and storing, of rainwater. It has been used to provide drinking water, water for livestock, water for irrigation or to refill aquifers in a process called ground water recharge.<br />Rainwater harvesting is a technology used for collecting and storing rainwater from rooftops, the land surface or rock catchments using simple techniques such as jars and pots as well as more complex techniques such as underground check dams. <br />
It is a method which has been used since ancient times and is increasingly being accepted as a practical method of providing potable water in development projects throughout the world. It has wide application also in urban and peri-urban areas where the reliability and quality of piped water is increasingly being questioned.<br />Rainwater can be utilized alone or together with other supply sources in residential, commercial and industrial projects where pure water is desired<br />
NEED OF <br />RAIN WATER HARVESTING<br /><ul><li> Of the total water on</li></ul> earth, only 3% constitutes<br /> freshwater. Rest is saline<br /> water in the oceans.<br /><ul><li> 11% of the total freshwater</li></ul> on earth is groundwater<br /> available upto a depth of<br /> 800m which can be<br /> extracted for use.<br />
<ul><li> Surface water is inadequate to meet our demand and we have to</li></ul> depend on ground water. So to increase the ground water table<br /> through artificial recharge and improve its quality.<br /><ul><li> Over-exploitation of ground water resource has resulted in</li></ul> decline in water levels in most parts of the country.<br /><ul><li> To increase soil moisture levels for urban greenery.
To provide supplemental water for the city's requirement.
It makes ecological and financial sense not to waste a pure</li></ul> natural resource available in large quantity on one’s roof.<br />
3 STEPS OF <br />RAIN WATER HARVESTING<br />1) Catchment: Any surface or the paved areas can be treated as catchment. Even the footpaths and roads can act as the catchment, as these areas too receive the direct rainfall. Rooftops are the best among them because of the large coefficient of run off generated from them and there are less chances of contamination of water.<br />
2) Conveyance : Conveyance system basically includes down pipes which collects the rain water from catchment to the storage tank. These down pipes are usually built during the time of construction. They need to be designed appropriately so as to avoid the loss of water during the conveyance process. <br />3) Storage : The storage system is designed according to the amount of water that is to be stored. The design and site of the storage system should be properly chosen. The areas which receives the rainfall frequently, there a simple storage system could be constructed, to meet the daily water requirements. Otherwise the areas which receive the lesser rainfall, there the storage systems are quite essential. Rain barrels, underground or open slumps are mostly used to collect rain water. The storage system should be properly sealed and should not leak. Using chlorine from time to time keeps the water clean. <br />
<ul><li>Storing of rain water on roofs of the houses: Rain water falling on the roofs of the houses can be stored in nearby wells, tanks and step wells or can be stored in houses through pipes. The rain water of roofs can also be stored in the water percolation tanks for recharging ground water.
Small bonding around the fields: Flow of rain water falling on the fields in checked by building small bounding around the fields. The water thus stored n the field percolates underneath and increases soil moisture.
Step farming: Soil moisture of step fields made along </li></ul> mountain slopes is being increased by checking rain water of <br /> these fields. <br />
<ul><li> Check dams on seasonal rivers and drains: Rain water is</li></ul> also stored behind the check dams constructed over the<br /> seasonal rivers and drains with the help of soil, stones and <br /> wood. These dams regulate the water supply and also help <br /> in controlling soil erosion to some extent. <br /><ul><li>Water percolation tanks: Rain water is stored in tanks </li></ul> constructed in lands unsuitable for agriculture. These tanks <br /> serve the purpose of recharging of ground water reserves as <br /> water stored on these. <br /><ul><li>Making of drains: Rain water is also being stored in the </li></ul> drains dug around the fields. <br />
Structures generally used in recharging of ground water are:<br />
<ul><li>Pits Recharge: Pits are constructed for recharging the shallow aquifers.
Trenches: These are constructed when the preamble strata is available at shallow depths.
Dug wells: Existing dug wells may be utilized as recharge structure and water should pass through filter media before putting into dug well.
Hand Pumps: The existing hand pumps may be used for recharging the shallow / deep aquifers, if the availability of water is limited. Water should pass through filter media before diverting it into hand pumps.</li></li></ul><li><ul><li>Recharge Shafts: With bore wells for recharging the</li></ul> upper as well as deeper aquifers, lateral shafts of 1.5 to<br /> 2m wide and 10 to 20m long depending upon<br /> availability of water with one or two bore wells is<br /> constructed. The lateral shafts are back filled with<br /> boulders, gravels and coarse sand.<br /><ul><li>Spreading Techniques: When permeable strata start</li></ul> from top then this technique is used. Spread water in<br /> streams by making check dams, cement plugs or a<br /> percolation pond may be constructed.<br />