INDIANS have always stored rain water, sometimes enough for several years in anticipation of droughts. In most parts, it rains only for three months -- during the monsoon. The country is full of indigenous water harvesting structures, known variously as eries, kulams, kuntas, cheruvus and johads. They show enormous diversity of construction and management and meet the needs of a large section of people even today.

Many systems also recharge groundwater and control salinity in deltaic regions. These systems help conserve soil, too. The number of rainy days varies from 15 days in parts of Rajasthan to 150 days on the coast. Sometimes, 50 per cent of an area's rainfall occurs in just 20 per cent of the rainy days -- causing flash floods and heavy top-soil erosion. The lakes and ponds hold flood waters and lessen flood damage.

Today, many of these systems are on the decline because of public apathy, breakdown of community and institutions and an indifferent government. Says Nirmal Sengupta, a professor at the Madras Institute of Development Studies, "The government doesn't recognise them as they are considered too minor. But if these minor systems are networked, a major system could be built."