No new projects on the Chambal River will be taken up until its environmental flows improve, the Standing Committee of the National Board for Wildlife (SC-NBWL) has said.
The panel, under the Environment Ministry, made it clear that only drinking water projects may be considered, and that too if no alternative is available. Environmental flows refer to the water needed in a river to sustain its ecosystem.
A report by the Wildlife Institute of India (WII), placed before the committee, points to a steady drop in the river’s flow. Discharge begins to fall from November and reaches near-zero levels by June.
"Monsoon season water availability is highest (more than 500 cubic metres per second during July-September) whereas the current average flow at Dholpur during May-June is about 25-50 cubic metres per second," according to the minutes of the 90th meeting of the committee, held on March 21.
The change in flow has affected wildlife. The Ganges river dolphin has shifted downstream compared to earlier distribution, as water depth has reduced.
The WII has estimated that a minimum flow of about 369 cubic metres per second is needed in the lean season to maintain a depth of three metres for dolphins and other species.
For a depth of five metres, the optimum flow is around 849 cubic metres per second. Other species are also affected. Adult and sub-adult gharial prefer water depths of more than four metres, while mugger crocodile avoid very shallow waters.
The committee has called for a basin-wide cumulative impact assessment and asked that connectivity between deep pools be maintained.
It has suggested that water withdrawals be allowed during July to September, when discharge is higher, while ensuring minimum flow requirements for aquatic life.
The Central Water Commission agreed with the observations and recommended expanding the study with inputs from the National Institute of Hydrology, the National Hydroelectric Power Corporation and the Ministry of Jal Shakti.