What is rainwater harvesting? As the name itself suggests, it is the collection and storage of rain water (during the rainy season) for use during periods of dry water.
Rain water can be harvested in two ways:
- collection and storage of water in tanks and reservoirs.
- storage of rainwater in subsurface rocks as ground water.
It goes without saying that there is an intimate relationship between surface water and ground water. Ground water sustains and replenishes surface water bodies during the dry season.
Due to the monsoon rains during the rainy season, India does not lack water. But the geographical and monthly distribution of rainfall is uneven. Thus, there is a need for rainwater harvesting. (Especially as only seventy per cent of rural households have access to safe drinking water.) Only thirty per cent of the surface water is used; the balance flows into the sea. Thus, there is a vast potential for rainwater harvesting measures.
Ground water should be replenished by a natural recharge process. But due to over-exploitation, ground water levels have shown a decline of more than four metres in some states. As there is a steady increase in ground water irrigation, the problem is only getting worse. Given the increase in population and urbanization, it is expected that all ground water resources would be used up by 2025. Already, shallow wells are drying, and groundwater quality is deteorating.
A related problem is that (salty) sea water is making inroads in costal areas, due to a fall in groundwater levels.
As regards rain water harvesting from roof tops, its viability is limited to certain regions, as the overall rainfall pattern in this country is shifting towards short duration and high intensity rainfall.
The author says that rain water harvesting projects must be taken up on an urgent basis. Especially as they are eco-friendly and cost-effective. Not to do so would only aggravate the various water related problems that the nation is already facing.