Rain Water Harvesting to augment ground water resources
Rain water harvesting is the technique of collection and storage of rain water at surface or in sub-surface aquifers, before it is lost as surface run-off. 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 rate exceeding that under natural conditions of replenishment.
Rain Water Harvesting Need
To overcome the inadequacy of waters to meet our demands.
To arrest decline in ground water levels.
To enhance availability of ground water at specific place and time and utilize rain water for sustainable development.
To increase infiltration of rain water in the subsoil which has decreased drastically in urban areas due to paving of open area.
To improve ground water quality by dilution.
To increase agriculture production.
To improve ecology of the area by increase in vegetation cover, etc.
Rain Water Harvesting Advantages
Cost of recharge to sub-surface reservoir is lower than surface reservoirs.
The aquifer serves as distribution system also.
No land is wasted for storage purpose and no population displacement is involved.
Ground water is not directly exposed to evaporation and pollution.
Storing water underground is environment friendly.
It increases the productivity of aquifer.
It reduces flood hazards.
Effects rise in ground water levels.
Mitigates the effects of drought.
Reduces soil erosion.
Design Considerations:
The important aspects to be looked into for designing a rainwater harvesting system to augment ground water resources are: -
Hydrogeology of the area including nature and extent of aquifer, soil cover, topography, depth to water level and chemical quality of ground water.
The availability of source water, one of the prime requisite for ground water recharge, basically assessed in terms of non-committed surplus monsoon runoff.
Area contributing run off like area available, land use pattern, industrial,residential, green belt, paved areas, roof top area etc.
Hydrometerological characters like rainfall duration, general pattern and intensity of rainfall.
Potential Areas
Where ground water levels are declining on regular basis.
Where substantial amount of aquifer has been de-saturated.
Where availability of ground water is inadequate in lean months.
Where due to rapid urbanization, infiltration of rain water into subsoil has decreased drastically and recharging of ground water has diminished.
Methods & Techniques
The methods of ground water recharge mainly are:Urban Areas
Roof Top Rain Water /Storm run off harvesting through
i) Recharge Pit
ii) Recharge Trench
iii) Tubewell
iv) Recharge Well
Rural Areas
Rain Water Harvesting through
i) Gully Plug
ii) Contour Bund
iii) Gabion Structure
iv) Percolation tank
v) Check Dam/ Cement Plug/ Nala Bund
vi) Recharge shaft
vii) Dugwell Recharge
viii) Ground Water Dams/Subsurface Dyke
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