WHAT IS RAIN WATER HARVESTING Rainwater harvesting is the accumulating and storing of rainwater for reuse before it reaches the aquifer. The principle of collecting and using precipitation from a catchments surface
WHY RAIN WATER HARVESTING Surface water is inadequate to meet our demand and we have to depend on ground water. To arrest ground water decline and augment ground water table To beneficiate water quality in aquifers To conserve surface water runoff during monsoon To reduce soil erosion Due to rapid urbanization, infiltration of rain water into the sub-soil has decreased drastically and recharging of ground water has diminished.
RAIN WATER PATTERN IN INDIA Total annual rainfall in India: 400 million hectare- meters (area x height) India’s area: 329 million hectares If evenly spread, average height: 1.28m Actual distribution: Highly skewed area-wise Thar desert receives less than 200mm annually, while Cherrapunji receives 11,400mm But almost every part of India receives at least 100mm annually Key: even 100mm annual rainfall sufficient if harvested properly and where it falls
RAIN WATER HARVESTINGTECHNIQUES : Roof top rainwater harvesting. Surface runoff harvesting .
ELEMENTS OF ROOFTOP RWH CATCHMENT COUNDITS FILTERS STORAGE FACILITY
METHODS OF ROOFTOP RWH Storage of direct use Recharging ground water aquifer - Recharging dug wells - Recharging pits - Recharging tube well
SURFACE RUNOFF HARVESTING Harvesting of surface runoff and storage of the same into reservoirs such as water pans makes it available for use when required. In this method of collecting rainwater for irrigation, water flowing along the ground during the rains will be collected to a tank below the surface of the ground..
TRADITIONAL RWH STRUCTUREBAWODI:Traditional step wells are calledvavadi in Gujarat, or baoris orbavadis in Rajasthan andnorthern India.They were secular structures fromwhich everyone could draw water.Most of them are defunct today.
JOHADSA johad is a crescent-shaped bund which isbuilt across a slopingcatchment to capturethe surface water beforeit runs off.Water accumulating inthe johad percolates inthe soil to augment thegroundwater. Thegroundwater then canbe used when there is norainfall.
POTENTIAL OF RWH Impacts on downstream flows. Reduce soil erosion. Increase the crop production. Increase infiltration and groundwater recharge. Improve food & economic security.
ADVANTAGE It uses local construction materials and labor. Sources of energy are not needed to operate the systems. The owner/user can easily maintain the systems. The water is convenient and accessible; valuable time and effort are saved in collecting and/or hauling water. It provides a supply of water to meet future agricultural needs.