Stable and steady rise in level of groundwater recorded in rainwater harvesting project sites, says CSE survey report

Rainwater harvesting can revive Delhi’s dwindling water table -- but only if the government stops paying lip service and gets serious, says CSE. Wants city government to work on water on a war footing and presents an action plan on what needs to be done. "Water will be the determinant for the future of India. Delhi must take its responsibility seriously," says CSE.

New Delhi, June 15, 2004: Rainwater harvesting can recharge the declining groundwater levels in cities. Data from 11 rainwater harvesting projects spread across Delhi shows an increase of 5 to 10 metres in the groundwater levels over two years. This is particularly important to view against the recent data of the Central Groundwater Board (CGWB), which shows an alarming decline of 2-10 metres in the water table in different parts of the city. But, even while the potential of rainwater harvesting is evident, the issue of access to water for all will require much more effort at the city level, than what is being done today.

At a meeting of the network of rainwater harvesters of Delhi, the Centre for Science and Environment (CSE) presented the results of its survey from May 2002 to May 2004 on the level of groundwater in rainwater harvesting sites; these sites have been designed by CSE. The data shows the following trends:

• The data collected before and after monsoons showed that every site recorded a sharp rise in water table -- ranging from 5 metres in Shriram School (Vasant Vihar) to roughly 10 metres in Janaki Devi College (Rajinder Nagar).

• In the Tughlakabad area, where CGWB records an alarming dip of 10 metres in groundwater table in just one year, the Jamia Hamdard University complex showed an increase from 47.5 metres in 2002 to 39.3 metres in 2004. In other words, not only has it checked the decline, it has stabilised and increased its underground water bank. This, when the university is dependent on groundwater to meet its needs. Put together, this is a remarkable gain of 20 metres in 2 years.

• The gains are evident in the second year, when a definite slowing down of the process of depletion was detected -- even in the dry season. In all the sites, the pre-monsoon water table in 2004 has remained higher than what was recorded in the same period last year.

"This vindicates our point that groundwater is like a bank account. We have to learn to live on the interest (recharge) and not on the capital of this reserve. In other words, we have to abstract only as much as we recharge. But today, the situation is so bad that we are mining this resource," says Sunita Narain, CSE director.

"This, I believe, is the greatest achievement of our project hosts. Through their rainwater harvesting efforts they have been able ensure that for at least three months in a year (July to August) the rate of recharge of groundwater is more than the rate of extraction. This process nurtures and replenishes the resource, and stabilises the annual rate of depletion," explains Narain. (View details of CSE's model projects).

This is particularly important, as the city is today very dependent on groundwater to meet its drinking water needs. But even as this effort of individuals and institutions showcases the potential of this technology, it is not enough to ensure a sustained, long-term impact on the capital’s groundwater situation, admits CSE.

This will require much more deliberate policy and action at the city level. At the meeting, CSE outlined the efforts as follows:

• Increase the harvesting of rainwater at the city level, by protecting and regenerating the tanks and ponds, which were found across the city but are lost today to land developers and to sewage and garbage. According to the Delhi government there are between 700-1,000 ponds in the city, crying for attention. These ponds are the sponges of the city – collecting its rainwater and recharging the groundwater table.

• Promote individual rainwater harvesting projects at the colony and household level, which improves the local groundwater levels. Ensure by law that all commercial users are required to harvest.

• Redistribute the water supply across the city to ensure equity. The availability of water in the city is adequate – over 200 litres per capita – but the problem is that while certain areas (New Delhi and the Cantonment) get over 400-500 litres per person, other areas do not get even 30 litres per person.

• Treat all the sewage collected in Delhi and recycle the water so that we do not pollute our rivers and destroy the water cycle.

"All this needs to be done on a war footing. We are losing time," emphasises Narain.

Not capturing the rainwater is a national waste. Delhi’s endowment of rainwater -- about 611 mm of rain per year with a total land area of 1,486 sq km – means that even with 50 per cent efficiency of the rainwater harvesting systems, Delhi still has water harvesting potential of 450 billion litres annually. This equals to about 35 per cent of the total water demand of the city.