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Wed23Apr2014

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Harvest from the skies

By Teresa Barat

Five model rainwater-harvesting projects in Delhi show how the city's fast-depleting groundwater table can be recharged and how the acute water scarcity could be tackled

Sometimes the Rain Gods co-operate. A group of 20 journalists were waiting to assess the merits and demerits of a rainwater-harvesting project at Shri Ram School, Vasant Vihar, Delhi. Just as the group stepped out on the grounds of the school, the skies darkened, there was a roll of thunder and big raindrops began to patter. A chance to see a working model!

The Centre for Science and Environment (CSE) in Delhi had organised a workshop for the media to review the working of five model rainwater-harvesting projects. CSE has been promoting water harvesting as a practical solution to recharge the city's fast-depleting groundwater table and meet the problem of water scarcity. Apart from the one at the Shri Ram School, CSE set up these projects at the Jamia Hamdard University, Panchsheel Park, Janaki Devi Memorial College and Mira Model School.

All these institutions were facing increasing water problems; the Delhi Jal Board (DJB) water simply did not suffice. Tubewells were drying up or had to be dug deeper and deeper for scarce, brackish water. With the Supreme Court directive against digging fresh borewells, help had to be sought from the skies. Dr Krishan Sehgal, President of the Panchsheel Park Managing Committee said, "We liked CSE's scheme because it was relatively inexpensive; it harks back to our ancient traditions and gives employment to local labour."

Water from roof run-offs can either be stored in tanks for direct use or for recharging groundwater, which is more feasible in a city like Delhi. Below a certain depth in the ground, the earth is saturated. This means that all the free spaces are filled with water. These are the groundwater aquifers that are formed by the collection of water over many years.

In Delhi, groundwater levels vary between 3 to 60 metres below the surface level. The metropolis relies heavily on groundwater because there is a huge gap between the demand and supply of water. Residents in many colonies of the city use groundwater through tubewells. Besides, several water-tanker and bottled water companies draw and sell groundwater. The heavy extraction of groundwater has led to an imbalance because the withdrawal of water is far more than the recharge.

According to CSE, rainwater harvesting can be adapted to suit different geographical and geological factors. The basic elements are: the catchment area (the surface that receives the rain) and the pipelines or drains that carry the rainwater to the harvesting system. The system can be designed for storage and use, or as a recharge facility to augment the groundwater aquifers. The latter can be done through old wells, borewells, recharge pits or trenches.

The cost of a harvesting system depends upon the size of the project -- from Rs 30,000 to Rs 100,000 or more (1US$=Rs 49). According to users in the institutions, the CSE projects have had the desired impact. The water table in these areas has risen by a metre or more. This, at a time when the water table is falling everywhere else in the city. "Earlier, drinking water would finish by 10 am. Now, there is always water in the taps. After installing the harvesting system, the school uses groundwater for gardening," says a student of Mira Model School.

Shri Ram School was the pioneer in Delhi in having the CSE harvesting system installed in May 2000. Students' clubs like the Green Brigade at Shri Ram and the Eco-Club in Mira Model do their bit by spreading the good word among friends and family. In fact, students of Shri Ram School have made presentations on the theme for residents' associations, hotels and other organisations.

In Panchsheel Park, a small harvesting system was first set up at the Panchsheel Club. When this proved successful, the Managing Committee installed rainwater harvesting for the entire colony at a cost of Rs 800,000. Rainwater is collected through a network of stormwater drains that feed 36 recharge wells. The positive impact of this initiative has encouraged many individual residents to opt for rainwater harvesting.

Certain limitations however, still exist. According to Dr Sehgal, the municipal corporation does not fulfil its civic duties -- the stormwater drains are not cleaned, so the residents' committee has to organise this. And unless householders maintain cleanliness outside their homes, the run-off water becomes polluted.

The rainwater harvesting system at Jamia Hamdard University is the largest in Delhi. Established in June 2001, the system has had a dramatic impact on the water table. Water is now available at a depth of 39-42 metres instead of 45 metres. The run-off from the neighbouring Jahanpanah forest is stopped by a check dam, fed into a sedimentation tank, and from there to a recharge borewell. Rainwater is also collected from the rooftops and paved areas. Besides, the University recycles and conserves water. One year after the system became operational, the University's dependence on water tankers was considerably reduced.

Rainwater harvesting has been, and still is, a viable option to reduce the water woes of Delhi's citizens. Its success in many parts of the world has been amply demonstrated. For instance, both Singapore and Hong Kong make extensive use of systematically harvested rainwater. Significantly, former President K R Narayanan had a rainwater harvesting system installed on the Presidential Estate.

In 2001, the Delhi division of the Ministry of Urban Development and Poverty Alleviation directed all housing societies with buildings that have a surface area of 100 square metres and above to install rainwater harvesting systems. While CSE applauds this decision, it also believes that rainwater harvesting should be a compulsory subject for students of engineering and town planning.

However, precautions against polluted water need to be taken seriously. CSE Director Sunita Narain says pesticides and herbicides should not be present in catchment areas. Although rainwater harvesting is not a panacea for Delhi's water scarcity, explains Narain, it is vital to replenish the city's heavily depleted groundwater reserves.

Since a large part of India's food production relies on groundwater, its depletion could threaten India's food security. Recharging the water table is a task that people at every level can undertake. As Mahatma Gandhi said, the task does not need 'mass production but production by the masses'.

Women's Feature Service