Delhi govt to build over 70 check dams in Asola Bhatti to conserve rainwater, prevent soil erosion
The Delhi government’s forest department is planning to build over 70 small check dams in the catchment areas of the Asola Bhatti sanctuary and the southern and central ridges to conserve rainwater and prevent soil erosion.
The project aims to retain water in the form of small ponds that will help recharge groundwater aquifers, bring up the depleting water table and also serve as a natural water resource to support wildlife and improve vegetation. These forests are considered the city’s green lungs. During monsoon, rainwater flows out of the forests into nearby colonies and drains and nutrient-rich soil is lost due to surface runoff.
According to officials in the forest department, the project has already been launched at the Asola sanctuary. Eleven check dams are already being built. These dams will help retain as much water as possible, which will gradually aid in raising the water table of nearby areas as well. It will also improve the soil quality and vegetation in the area.
The sanctuary is located on the southern ridge and is spread across 1,960 hectares. It is part of the northern Aravallis and serves as a carbon sink for the national capital and a potential shelterbelt against desert storms.
The decision to build check dams was taken by the Delhi government after the Delhi High Court told the city government last year to trap rainwater and check soil erosion in protected forest areas.
“Check dams are small dams that are built across a water channel or a drainage ditch (depression) to counteract erosion by reducing the velocity of the flow of water. It prevents the soil from erosion during rainfall and allows water to be retained in the form of small pools or waterholes where wild animals can drink and bathe. They also help natural vegetation grow by retaining moisture,” said Ishwar Singh, the principal chief conservator of forests (PCCF) and head of the forest department.
A senior forest official said that their departments has undertaken an extensive survey to identify the catchment areas at all three locations. “So far at Asola, we have identified around 30 sites where check dams of about 2-4 feet in height will come up. A survey to identify 20 more sites is going on. Also, three or four bigger dams of 6-8 feet in height will be constructed in the sanctuary area. Besides, on the southern and central ridges, 8-10 dams each will come up. These forests already have a few bigger check dams we constructed a few years ago,” the official said, not wishing to be named.
“The first batch of 11 dams has been set up in the forest area behind Sangam Vihar. At present, work is being undertaken at the Neeli Jheel and near the Shahurpur village. Work has also started at the central ridge,” the official added.
The forest department has roped in the Bombay Natural History Society (BNHS) for the project. Sohail Madan, an ecologist and manager of the BNHS Conservation Education Centre at Asola Bhatti sanctuary said that three kinds of check dams—gabion rock dams, soil embankment dams and grass dams—are being built on seasonal streams.
“Check dams are effective, low-cost and do not disturb the forest as such. They will be of immense help in retaining soil and moisture at a place like Asola, which has steep slopes where the water and the silt run down fast,” said Madan.
CR Babu, professor emeritus and head of the Centre for Environmental Management of Degraded Ecosystems (CEMDE) at Delhi University, said that check dams are a traditional method of rainwater harvesting in larger landscapes such as forests that have bigger surface drainage channels. “There are many roles that these dams play, from increasing the capacity of groundwater recharge, raising the water table and retaining moisture for plant growth to serving as grassland habitats, which enrich the overall biodiversity. It is a good technique to prevent soil erosion. Some of the deeper streams serve as a water resource even during the dry season,” said Babu.