Two more reservoirs to store Yamuna’s rain run-off, bolster city drinking water supply

A water stressed city, Delhi has daily supply of 935MGD (millions gallons daily) and it is estimated to be 300MGD short of the city’s projected demand of 1,236MGD.

The Delhi government has approved the construction of more catchment reservoirs along the Yamuna to store the river’s excess monsoon water and thereby augment the city’s drinking water supply. Two such pilot reservoirs were approved on Friday in a review meeting chaired by chief minister Arvind Kejriwal.

A ragpicker stands on the banks of the river Yamuna in New Delhi. (AFP)

A water stressed city, Delhi has daily supply of 935MGD (millions gallons daily) and it is estimated to be 300MGD short of the city’s projected demand of 1,236MGD.

“Our plan is to store the excess water reaching the Yamuna during the monsoon in these reservoirs and purify it. Once the strategy is proved successful, more such reservoirs will be built to divert excess water from the Yamuna and augment supply in Delhi,” Kejriwal said after the meeting.

The first two pilot reservoirs will come up over an area of 479 acres and will be able to store 1,958 million gallons (MG) of water, a government official said, asking not to be named.

“First, a catchment wetland reservoir over 459 acres will be created at the upper end of the pondage area of Wazirabad reservoir on the western bank of the river. It will store floodwater up to 1,735 million gallons. A second smaller reservoir, over 20 acres, will be set up away from river. It will have a depth of 10m and will be able to store 223 million gallons,” the official said.

A second official said the new project is only taking forward a pilot project carried out in outer Delhi’s Palla. “We have successfully carried out three cycles of pilot projects by creating shallow reservoirs in Palla where groundwater increase of up to two metres has been observed after each monsoon flooding cycle. This (the two pilot projects) is an extrapolation of the same concept -- more reservoirs will be created upstream of Wazirabad where the river water is clean,” the official associated with the Palla mega reservoir project said, requesting anonymity. The irrigation and flood control department started the Palla project in 2019 — a shallow pit was dug over 45 acres to hold excess rainwater.

Kejriwal said the government is taking these steps to resolve the drinking water shortage in Delhi. “Officials have been directed to proceed with both proposals so that work on the pilot projects can be started soon. All storage structures will be developed upstream of Wazirabad reservoir, extending to Palla, and they will have minimal or no adverse impact on the river ecology,” he said.

Data over the past decade suggests that on average, 18 flooding cycles happen in the Yamuna floodplains during the monsoon, when water levels go above 208 metres.

Each cycle yields around 2,100 million gallons of water.

The government spokesperson said the strategy, after assessing these two projects, is to develop capacity to store about 32,203 million gallons of floodwaters.

“First, 20 catchment reservoirs, each spread over 200 acres, will be set up with a depth of two metres to 8,552 million gallons. A 1,000 acre expanded pondage area of the Wazirabad reservoir, with a 2m depth, will be able to store 2,138MG of water,” the spokesperson said.

Manoj Misra, an environmental activist and the head of the Yamuna Jiye Abhiyan, said the project should be carried out in an ecologically appropriate manner. “If the retention can be facilitated in an ecologically proper manner, then it will fasten aquifer recharge,” he said.