Retrofitting Wetlands
An image of a wetlandPhoto credit: Brittanica

Retrofitting Wetlands

There is a science behind restoring a destroyed wetland and it involves local communities too

Water has been revered in the Indian culture as 'Mother' and even as 'Goddess'. Not only does water satiate thirst and help plants grow, it is even considered a purifier of body and soul.

Apart from the natural water bodies such as seas, rivers, lakes, ponds and so on, wetlands were created in cities like Chennai to collect rainwater and help with the irrigation as well as provide drinking water to those settled around it.

These wetlands were created as networks, and not as islands - canals connecting the wetlands such that when one overflowed, the second rung got filled up and so on. This helped manage heavy rains and prevent flooding, and provide with enough water during dry months.

Unfortunately, the British, considering these bodies unproductive, classified them as 'wasteland' during their rule over India. Sadly, that classification continues to this date.

“Not only has that classification remained, but the lack of understanding of their significance in rainwater harvesting is evident in the way they are sacrificed for buildings. Wetlands are giving way to residential buildings, shops, roads and other constructions,” explains Dr RJ Ranjit Daniels, Trustee, Care Earth Trust.

Pollution and construction have been two key reasons for losing the wetlands. Due to encroachment, the wetlands are not connected anymore, because of which when one wetland fills up, it floods the whole area. Management of these bodies has become a challenge.

Indeed, a report reveals that Chennai has only 33% water bodies remaining.

Care Earth Trust’s own study in 2016, after the Chennai floods in 2015, showed that more than 150 water bodies, part of a flood mitigating system in the city and its suburbs, had been reclaimed for development.

Only 15% of the city’s wetlands remained, down from the 80% when Chennai covered a smaller area. Over the years, for the sake of development, wetlands have been reclaimed to build highways, flyovers, residential complexes, shops etc.

“The problem of water logging during rains is also because the network does not exist anymore and the water has no channel to direct it to the next wetland,” points out Jayshree Vencatesan, Trustee of Care Earth.

Therefore, any efforts at restoration are severely impeded by two factors - the enormous pollution over the years and the absence of a network of wetlands to continue to serve the purpose. Continued encroachments also pose a severe challenge.

“We are also constrained to construct cement structures to store the water as inlet and outlet functions have become redundant,” explains Ranjit. Only limited area is provided by the Public Works Department for wetland and the buffer land around it, and often, even that stretch is encroached upon.

Care Earth focuses more on retrofitting the wetlands to develop them into storage bodies and for ground water recharging.

The goals are:

  • Retention of the water systems

  • Maximising capacity

  • Preventing groundwater depletion

  • Ensuring species diversity

  • Nominating target species

The effort involves right from doing a topographical survey of the wetland to analysing the biodiversity up to five kilometres around the wetland to socio-economic survey of the community dependent on it, enumerate the species, identify the ones that need to be protected and those that need to be removed.

Each restoration/retrofitting effort needs at least a couple of years due to the number of pre, during and post steps involved.

“It is not a number based model. We undertake projects one at a time because it takes that kind of time and effort. Each wetland needs a different approach,” Jayshree emphasises.

After a sediment and soil analysis, the wetland is desilted and dredging undertaken. For this purpose, it is divided into segments for greater efficiency. The muck removed is assessed from time to time and removed to avoid eating into the designated wetland area. “We are very particular about not compromising on the wetland area,” emphasises Jayshree.

Since restoration to the original state of purity is impossible, benchmarks are set and, if required, corrected mid-course.

Then greening efforts are undertaken by planting herbs. “Many create functional spaces for activities, aesthetics and the like. We try to do that, but that is not our purpose.

Trees are planted only to demarcate and consolidate boundaries and the choice is normally limited to palms, neem, and other riparian species,” explains Jayshree.

Plant material that can stabilise the bund, that will allow flow of water, recharging, and not plants that sap all water and grow are important.

Care Earth works with a team of hydrologists, civil and environmental engineers, biodiversity experts and even army personnel, each contributing significantly in their respective areas.

“We need that kind of diversity and discipline,” says Jayshree.

Each wetland has its own requirements and therefore its own pace of restoration. Sometimes only 10-20% improvement is possible.

Though the central and state governments are also taking efforts to improve the quality of the water bodies, it requires greater awareness, coordination and cooperation to make these bodies truly benefit the society.

(This article is sponsored by Care Earth Trust as part of an awareness campaign on water conservation)

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