Water Harvesting Dams: Experience at Bunga

March 7, 2012

Morni Hills receive an average annual rainfall of 1200 mm and 80% of it is received during the 3 monsoon months. Most of the precious rainwater is lost as run-off and it drains into the Ghaggar and Tangri rivers that originate in these hills. These rivers flow torrentially during the rains causing havoc in Ambala and Patiala that lie downstream only to run dry thereafter until the next rains. The Shivaliks are low, fragile hills of mud and are prone to erosion and land slides. The sub-tropical, dry-deciduous forest cover of the hills has been facing degradation over the past century due to pressure from excessive grazing and fuel wood extraction by a community completely dependant on rainfed crops and livestock rearing for meeting their survival needs. It was realized that the forests could not be saved without reducing the dependence of the local communities and efficient water management held the key to the problem. There was a need for harvesting the rainwater for providing a year round, regulated supply of water for meeting the crop, livestock and drinking water requirements. Increased availability of water during the crop growing season would increase the productivity of agriculture and the availability of green fodder that would help reduce the dependence on the surrounding forests. As part of this effort a series of earth fill dams have been constructed in the past 3 decades across seasonal nalas all over the Shivalik region including the Morni hills, for harvesting the rain water in the monsoon months to provide a water source during the dry season.

The local village community was involved in providing labour for the earth excavation in the submergence area and also for the subsequent management of the dam. The dams provided a major boost to the crop yields and availability of fodder and the cost of construction of dams was believed to have been recovered in 3 to 4 years due to increased crop yield and increased milk production. The daily drudgery of women folk in carrying water in pots from distant watering holes was significantly reduced. The landless got employment during the constrution phase and subsequently as farm hands. The gains were, however, shortlived as most reservoirs silted up within 10-15 years. Desilting is a costly affair especially where local communities fail to pitch in with their resources and look to the State for all their solutions. The problem of siltation is compounded by damage to the protective green cover by fuel wood extraction and excessive grazing in the catchment area of the dam that makes the soil loose and susceptible to rain water erosion. Plantation of soil binding grasses and shrubs and trees together with building of stone check dams help reduce siltation. The local community has to build social pressure against over-exploitation of forest resources.

One such water harvesting dam was built across a nala at Bunga in the Morni foothills in 1984, at a cost of 40 lac rupees, thereby creating a large reservoir with 60 ha.metre storage capacity.The 115 metre long, 14 metre high dam, however, got silted over the years until 10 metres of height was lost to silt and the storage capacity of the reservoir was reduced to less than 25% of the original level. The dam wall was then raised by 2 metres in 2003 to increase the storage to 27.56 ha. metres. A 3.7 metre high coffer dam with a storage capacity of 2.42 ha.metres was built upstream on the nala to check the flow of silt into the reservoir. The Bunga villagers saved the dam in August 2004 when 3 days of continous rain breached the coffer dam and the spill way of the main rervoir could not cope with the heavy inflow. The villagers sand bagged the embankment and lowered the spill way by removing its top layers to facilitate faster spill over and to reduce pressure on the dam. Today, the openings for the pipes laid for irrigation are buried under silt and the dam does not provide water for irrigation. The lake serves the purpose of a large village pond and is used for meeting the water needs of the cattle by the villagers. The lake has led to raising of water table from 550 feet to 450 feet thereby lowering the cost of boring tubewells. Most of the smaller, natural village ponds remain full to capacity for most part of the year.

A smaller reservoir was created by a second dam built in 1986 and an extensive network of pipes was created for carrying water to the fields lying downstream. The pipes openings are, however, covered by silt.

The two lakes have developed into minor eco-systems and the wetlands today have a considerable bird population. The lakes are a source of water during the dry summer months for the wild animals. Teams of grey langurs can be frequently spotted drinking water from the lake. Leopards, jackals etc have been sited in the forest around the lakes. The dams need to be protected for their beneficial impact on ecology of the area. The benefits for wildlife conservation need to be studied and properly documented.

Bunga main reservoir (April, 2012)

Bunga small reservoir

Spillway and irrigation pipes at smaller reservoir

Grey Langur family drinking water at Bunga lake

View of plains from Bunga dam

Bunga Village

Bunga Dam

Reference:
1. The Impact of Water Harvestin Dams and Project Experience by Dr. S.S. Grewal (2008)

2. Indirect Economic Impacts of Dams: Case Studies from India, Egypt and Brazil, Editors: Ramesh Bhatia, Rita Cestti, Monica Scatasta, RPS Malik. The World Bank and Academic Foundation, 2008,

Filed in: Environment

About the Author ()

An environmental enthusiast who loves tramping through the hills in search of the picturesque.

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