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April 2007

 

Water supply: are there solutions?

- Carel

“A massive artificial recharge is the best solution to counter the groundwater depletion of the area,” says Jeen Kootstra.

 

Map showing the location of Auroville south of the drainage network feeding Kaluvelly tank.


The February 2007 issue of Auroville Today carried an article on how to ensure an improved and continuous water supply for Auroville and its surrounding villages. A study made by Dutch specialist Eri Salomé, published in January, emphasized the need for a regional water management authority, responsible for the entire area – Auroville and the surrounding villages. It would handle water supply and distribution; prescribe appropriate solid waste and waste water systems to prevent ground water pollution; promote rain water harvesting and water re-use, and help install appropriate irrigation techniques to lessen water requirements for agriculture.

In February a second report was published, this time on available water resources. Dutch engineer Jeen Kootstra detailed a number of possibilities to secure the water supply for the region.

The groundwater situation: problematic

The groundwater situation in the area is problematic. As it is the only resource readily available at low cost, water is over-extracted. The yield from many wells has dropped considerably over the last few years. Auroville too suffers from less yield. As an intermediate solution, Kootstra proposes that water from the groundwater-rich Auromodèle area near the sea be pumped to Auroville's city centre. He warns however, that this source might only be reliable for a short period, probably no longer than five to ten years. “The hydrogeological formations below Auromodèle are not yet understood,” he says. “We do not know why there is no seawater intrusion in the aquifer and how long the groundwater resources will last.” The indications are not positive. Kireet, who has been building dams in the area to harvest rainwater, reports that the groundwater level has already decreased by 5 metres in the past five years due to increased pumping. The Bommaiyarpalayam panchayat has recently dug two wells in the same aquifer to provide its coastal villages with water; the village of Kuilapalayam relies on the same source, and many private individuals are also sinking wells. “It may be just a matter of time before all these wells pump saline water,” says Kootstra. “But this would be a disaster, as seawater intrusion into the groundwater is an irreversible process.”

Groundwater recharge

Can anything be done to solve the problem of excessive groundwater withdrawal in the wider region? Could the groundwater level be improved through artificial recharging? Kootstra considers this the best solution, but warns that “measures need to be substantive to have any meaningful effect.” Luckily, a significant source is within reach. Kootstra proposes to study to what extent surface water can be drawn from the drainage network feeding Kaluvelly tank north of Auroville and be injected into the groundwater through recharge wells – wells that are similar to tube wells and which are used to “pump in” treated surface water.

“This area is one of the main ‘natural recharge areas' of the region. Kaluvelly receives approximately six times more rainwater than it can store, and the excess goes to the sea. If part of this could be purified and infiltrated, it would be the best long-term solution.” Kootstra estimates that the study into the feasibility of this option shouldn't take more than 5-6 months. “If the study proves that this option is feasible, the new water organisation should propose this to the concerned authorities of Tamil Nadu. It would be the best long-term solution for the entire region, Auroville included.”

Rainwater harvesting

Apart from artificial recharge, Kootstra also stresses the need to greatly increase natural rainwater harvesting to improve the groundwater level. He proposes that a hydrogeological model be made to identify suitable infiltration areas in the region. Further he proposes that, as Auroville should be an example to the area, all houses in Auroville should have rainwater harvesting systems.

Waste water

The need for proper waste water management was also re-emphasized. In the actual and near-future conditions of Auroville, says Kootstra, decentralised waste water management is appropriate. Only at a later stage could a more centralised solution be implemented for a part of the city area. He recommends that all Auroville households have facilities for treating their waste water and re-use the effluent. Standards for safe effluents have to be set. Wastewater treatment systems have to be regularly checked for efficiency and effluent quality. The effluent needs to be safe for gardening or for recharge. “Groundwater can no longer be used for gardening,” says Kootstra. “Instead, treated waste water and harvested rain water should be used. Gardens should be laid out in accordance with water availability and not according to the unsustainable ideas of Aurovilians.” Kootstra hopes that, “with Auroville as a showcase, the surrounding villages will gradually follow suit.”

Puducherry's waste water

Puducherry's wastewater reception plant is situated near the community of Forecomers. Daily, 13,000 million cubic metres of untreated waste water are released into the ground. “We don't know the underground flow pattern of all that water,” says Kootstra. “Does it flow towards the sea? Which course does it take? Does it pollute the groundwater? Or is it possible that the polluted water and the ground water don't mix and that the groundwater flows more or less around that massive bulge of polluted water? A long-term study is required.”

Another question is if Puducherry's wastewater could be cleaned and reused for irrigation or safe groundwater recharge. Auroville's Centre for Scientific Research has a long-term project, in cooperation with the Centre for Ecological Restoration of the Smithsonian Institute, to study appropriate treatment systems for Puducherry's wastewater. The ultimate objective would be to use treated water for aquifer recharge and irrigation purposes, for the benefit of the whole area. This project, however, is still nascent. Another project aims to deal with Puducherry's solid waste dump next to the sewage farm. The French organisation ADEME (the French Agency for Environment and Energy Management) in collaboration with INTACH (the Indian National Trust for Art and Cultural Heritage) Puducherry will start work on that aspect.

Desalinated sea water

Kootstra considers desalination of sea water only a long-term solution, as at present the costs are prohibitive. However, a potential location for a sea-water desalination plant and a corridor for a transport pipeline to Auroville should be identified, for future eventualities.

Matrimandir gardens and lake

In all likelihood, a sufficient volume of excess rainwater from the Matrimandir oval – the area situated inside the Matrimandir Lake comprising the Matrimandir and its gardens – can be harvested and used to irrigate the gardens all year around. Groundwater will probably not be required.

Kootstra doesn't see a function for the Matrimandir Lake in the future city's water supply system. Instead, he considers that “the lake and its gardens complete the Matrimandir to form a pearl of serenity and beauty in the centre of Auroville.” He proposes that the lake be designed from this perspective, be built in sections and that the first filling be done with rainwater. It's still unclear where the water will come from to keep the lake at the required level to counter the effects of evaporation.

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