Rain Water Harvesting
v Water forms the lifeline of any society. Water is essential for the environment, food security and sustainable development.
v All the known civilizations have flourished with water source as the base and it is true in the present context too.
v Availability of drinking water and provision of sanitation facilities are the basic minimum requirements for healthy living.
v Water supply and sanitation, being the two most important urban services, have wide ranging impact on human health, quality of life, environment and productivity.
v Despite the technological advancements, the global scenario still remains grim, as all the inhabitants of the world do not have access to safe water and adequate sanitation.
Rain Water Harvesting:
v Rain water harvesting is one of the most effective methods of water management and water conservation.
v It is the term used to indicate the collection and storage of rain water used for human, animals and plant needs.
v It involves collection and storage of rain water at surface or in sub-surface aquifer, before it is lost as surface run off.
v The augmented resource can be harvested in the time of need. Artificial recharge to ground water is a process by which the ground water reservoir is augmented at a rate exceeding that under natural conditions of replenishment.
v The collected water is stored and pumped in a separate pipe distribution. This is a very useful method for a developing country like India in reducing the cost and the demand of treated water and also economising the treatment plants operation, maintenance and distribution costs.
Need:
1. To overcome the inadequacy of surface water to meet our demands.
2. To arrest decline in ground water levels.
3. To enhance availability of ground water at specific place and time and utilize rain water for sustainable development.
4. To increase infiltration of rain water in the subsoil this has decreased drastically in urban areas due to paving of open area.
5. To improve ground water quality by dilution.
6. To increase agriculture production.
7. To improve ecology of the area by increase in vegetation cover etc.
Advantages:
1. The cost of recharge to sub-surface reservoir is lower than surface reservoirs.
2. The aquifer serves as a distribution system also.
3. No land is wasted for storage purpose and no population displacement is involved.
4. Ground water is not directly exposed to evaporation and pollution.
5. Storing water under ground is environment friendly.
6. It increases the productivity of aquifer.
7. It reduces flood hazards.
8. Effects rise in ground water levels.
9. Mitigates effects of drought.
10. Reduces soil erosion.
Potential Areas:
1. Where ground water levels are declining on regular basis.
2. Where substantial amount of aquifer has been de-saturated.
3. Where availability of ground water is inadequate in lean months.
4. Where due to rapid urbanization, infiltration of rain water into subsoil has decreased drastically and recharging of ground water has diminished.
Methods and Techniques:
The methods of ground water recharge mainly are:
Urban Areas:
Roof top rain water/storm runoff harvesting through
a. Recharge Pit
b. Recharge Trench
c. Tubewell
d. Recharge Well
Rural Areas:
Rain water harvesting through
a. Gully Plug
b. Contour Bund
c. Gabion Structure
d. Percolation Tank
e. Check Dam/Cement Plug/Nala Bund
f. Recharge Shaft
g. Dugwell Recharge
h. Ground Water Dams/Subsurface Dyke
h.
Rooftop rainwater harvesting (RTRWH)
v Rooftop rainwater harvesting (RTRWH) is the most common technique of rainwater harvesting (RWH) for domestic consumption.
v In rural areas, this is most often done at small-scale. It is a simple, low-cost technique that requires minimum specific expertise or knowledge and offers many benefits. Rainwater is collected on the roof and transported with gutters to a storage reservoir, where it provides water at the point of consumption or can be used for recharging a well or the aquifer.
v Rainwater harvesting can supplement water sources when they become scarce or are of low quality like brackish groundwater or polluted surface water in the rainy season. However, rainwater quality may be affected by air pollution, animal or bird droppings, insects, dirt and organic matter. Therefore regular maintenance (cleaning, repairs, etc.) as well as a treatment before water consumption (e.g. filtration or/and disinfection) are very important.
