The Hindu Business Line : `Man-made aquifers good enough to store rainwater'

MANMADE aquifers are as effective as natural ones for purposes of storage and retrieval of rainwater, according to Mr K.R. Gopinath, Chairman of Chennai-based KRG Rainwater Harvesting Foundation.

Speaking to Business Line, he said certain places do not have natural aquifers. In such cases, it is possible to construct artificial aquifers and to good effect.

The term ``aquifer'' may be scientifically defined as a formation that contains sufficiently saturated permeable material to yield significant quantities of water to feed extraction structures like open wells and bore-wells. To avoid depletion of groundwater table, aquifers need to be recharged by making more quantity of rainwater percolate into the earth through rainwater harvesting.

A rainwater harvesting system runs on the principle of seepage of water into the ground. Owing to various soil features, rainwater is often obstructed from reaching an aquifer that is several metres underground. Water is made to infiltrate into an aquifer through an artificial recharge structure. Thus, rainwater falling on the surface has a smooth passage to the aquifer, where it is stored; from there it can be retrieved for future use

According to Mr Gopinath, shortage of water, even for drinking, has become too common a cause of worry in recent times. Experts are of the view that rain, the major source of water, needs to be tapped to the fullest extent possible and be used to recharge underground aquifers.

Not all rainwater that falls on the ground seeps into the soil. Most of it flows out as a stream or as run-off. The topsoil can hold only a fraction of water that falls on it and the rest gradually percolates down, depending on the type of soil, and joins the aquifers.

Rainwater harvesting is a traditional but scientifically proved technology applied to augment the level of groundwater both quantitatively and qualitatively. It does not imply a costly process or a cumbersome constructional scheme. On the other hand, it is an economical and natural solution for drinking water problem through artificial recharge of aquifers.

Being not energy or labour-intensive, rainwater harvesting can be a cost-effective alternative to other water-accruing methods such as desalination of seawater and diversion of rivers. An added benefit is prevention of intrusion of seawater into coastal regions. Rainwater harvesting also helps build inland water tables, thus thwarting any attempt by the sea to push salty water into coastal regions and damage fresh water aquifers.

Yet another benefit from rainwater harvesting is the all-round improvement in soil moisture content. This will go to make the soil fertile and, hence, conducive for agriculture.

For an average rainfall of 1,000 mm, approximately 40 lakh litres of rainwater gets collected in a year in one acre of land, after evaporation. On the basis of this calculation, Kerala, which has an annual rainfall of 2,500 mm per year, is estimated to account for 100 lakh litres in rainwater that falls on a ground of one acre in a year. Keeping this calculation in view, the State offers tremendous scope for implementing rainwater harvesting schemes, says Mr Gopinath.