New Delhi: Last week, the Supreme Court overrode the ban imposed by the National Green Tribunal (NGT) on desilting and dredging activities in Rajasthan’s Bisalpur Dam without environmental clearance. The ban was lifted taking into account the “acute water shortage” in the region, especially during the intense heat.
The apex court was informed that the desilting and dredging of the Bisalpur Dam in Tonk district aimed at restoring its storage capacity, which has been reduced from 1,095.8 MCum (million cubic metres) in 2004 — when it was impounded — to 1029.9 MCum.
Environmentalists and local social activists, however, are not convinced, with many saying conducting an environmental assessment is the most scientific way of going about the process of desilting the dam. ThePrint breaks down the issue.
What is the contention?
In November last year, the NGT banned desilting, dredging, mineral extraction and disposal from the Bisalpur dam without obtaining an environmental clearance, which is mandated under the Environmental Impact Assessment Notification 2006.
The Green Court also directed the Eastern Rajasthan Canal Project Corporation Limited (ERCPCL) to comply with all environmental laws and obtain the required consent, NOCs, and clearances before proceeding with desilting the dam.
The bench said that desilting or dredging activities in the guise of mineral extraction through mining operations cannot proceed without adherence to environmental laws.
This order was in response to a petition by a local resident and activist challenging that the tender issued to desilt the dam did not comply with the Sustainable Sand Mining Management Guidelines of 2016 and the Enforcement and Monitoring Guidelines for Sand Mining of 2020.
Environmentalist Himanshu Thakkar, who is a coordinator with the South Asia Network on Dams, Rivers and People (SANDRP) — an informal network of organisations working on issues related to water, and focusing on issues associated with large dams — explained that the Bisalpur Dam is relatively new and did not require desilting so urgently and frequently.
“There are bigger and older dams like the Bhakra Nangal and Hirakund Dam that have never been desilted. It is not economical to do so,” Thakkar said.
He also pointed out that the dam has reportedly been filled to capacity only three to four times since becoming operational, making it less prone to impacts from silt formation.
“Silt deposition only happens when the dam fills to capacity and excess water floods the surrounding areas. In such cases, you can claim that desilting can help increase the dam’s capacity and make it more efficient,” he added.
Bhim Singh Rawat, another environmentalist from SANDRP, said that an environmental assessment is a scientific way of proceeding with the de-siltation process. It will ensure that excessive mining is not conducted and that the dam’s structure and aquatic life are not damaged.
“How frequently a dam needs to be dredged and desilted depends on its location, geography, topography, and flooding areas,” he said.
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Dependence on Bisalpur Dam for water
The Bisalpur Dam reservoir is the primary source of irrigation water for Sawai Madhopur and Tonk districts of Rajasthan. It also supplies drinking water to Ajmer, Jaipur and Tonk.
The ERCPCL said before the Supreme Court that it had already dredged one lakh metric ton of sand from the dam. If this were not disposed of before the monsoon onset, it would harm the dam’s structure and the nearby areas. The Rajasthan government, which was also a party in the case, also informed the court that if the NGT ban was upheld, it would cause “serious water scarcity in parts of Rajasthan”.
The court was informed that sedimentation had reduced the dam’s water storage capacity and deprived around 3.5 million people of drinkable water. It was also argued that desilting was the only way to cater to the needs of the people residing in the three districts.
The Bisalpur irrigation-cum-drinking water supply project is constructed near the village of Bisalpur, about 30 km southeast of Todaraisingh and 50 km north of Tehsil Deoli in the Tonk district of Rajasthan. More villages have demanded to be included in the dam’s supply chain.
Ahead of the 2024 Lok Sabha polls, residents from the Jaikmabad village, which is only about 20 km from the dam, also demanded that they be given water from Bisalpur. The village is facing an acute water shortage.
“Water scarcity is a major problem in Rajasthan, and Bisalpur is a lifeline for residents in Tonk and Jaipur. Over the last few years, because of low rainfall, the dam did not fill much. There has been a major water crisis because of it,” Ravi Singh, a local water activist in Tonk district and the co-founder of the citizens’ group Sadbhavna, told ThePrint.
This is when the state is reeling under a severe heatwave, which will continue till the arrival of monsoon.
According to India Meteorological Department (IMD) recordings, the maximum temperature in many cities in Rajasthan is hovering over 50 degrees Celsius. On 28 May, Churu recorded a maximum temperature of 50 degrees Celsius; Ganganagar, 49.4 degrees Celsius; and Phalodi, 49 degrees Celsius.
How is it done in other countries?
In many parts of the US, South Africa and Australia, dams are desilted regularly but not with excavation machines. The most popular method is sediment bypassing, where a bypass channel is created around the reservoir area. The sediments are deposited in a designated area from where it can be removed.
Other methods practised internationally are sediment sluicing and trapping. Both these methods involve setting up natural sediment traps in the dam so that water containing sediments and gunk automatically passes into the primary reservoir area leaving the sediments behind.
A study conducted by the United States Geological Survey found that sediments can reduce the storage capacity of a dam by up to 50 percent. The study also found that sediment can clog pipes and intakes, disrupting water supply. Sediment deposits can also degrade the quality of water.
(Edited by Uttara Ramaswamy)
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