DAMS ON RIVER BHAGIRATHI (POSITIVE AND NEGATIVE EFFECTS), UTTARKASHI, UTTARAKHAND
Dams on river Bhagirathi Blog | UCBMSH – Life Science Degree courses college in Dehradun ( Doon ) , Uttarakhand , India .
In the River Bhagirathi basin both large and small hydroelectric projects are already operational, some are in constructional phase and still others are in planning phase. There are 18 dams along the Bhāgirathi River, either in operation, under construction or planned. Presently three hydro- power project namely Maneri Bhali I, Maneri Bhali II and Tehri Dam are operational on River Bhagirathi.
In view of the concerns about its effect on the fragile ecology in the Himalayas (Uttarakhand), the government has shelved two mega hydroelectric projects on the River Bhagirathi. According to a report published, the government has decided not to initiate the process for construction of two projects – the 381MW Bhaironghati and 480MW Pala-Maneri – which were planned to built on the upper reaches of the river. The government’s decision to shelve the projects will allow the Bhagirathi to flow in all its glory all through the year – a demand also pitched for by Hindu organizations, as they wanted the Bhagiarthi to flow unchecked till it reaches the plains as River Ganga. The report also claimed that the government might even decide to shut down the ongoing 600MW project at Loharinag-Pala in the wake of an assessment by experts on the environmental costs of the mega dam.
Management of river waters has been, one of the most prime issues under consideration. The dams and reservoirs world over have been playing dual role of harnessing the river waters for accelerating socio-economic growth and mitigating the miseries of a large population of the world suffering from the vagaries of floods and droughts. Dams and reservoirs contribute significantly in fulfilling the following basic human needs viz., Water for drinking and Industrial Use, Irrigation, Flood Control, Hydro Power Generation, Inland Navigation and Recreation.
Besides the importance of dams there are also some negative effects of dams as the impoundments created by dams can greatly affect stream temperatures, and although dams create other problems as well, their temperature effects can be significant. The majority of impoundments are the result of small, surface-release dams, and they are most likely to raise downstream temperatures during summer. These impoundments act like small lakes and beaver ponds that tend to increase stream temperatures because they increase the residence time of water and the surface area exposed to solar radiation. Coldwater fish species generally were less abundant below than above dams, but overall fish diversity increased below dams due to the influx of warm water species (Lessard and Hayes, 2003).
Large, deep impoundments that release water from the bottom of the dam have a very different effect. Because the hypolimnion of reservoirs is relatively cool throughout the year, deep-release dams result in downstream temperatures that are cooler in summer and warmer in winter than the normal (Stanford and Ward, 1979). Larinier (2001) concludes that the construction of dams on rivers block or delay upstream migration and thus contribute to the decline and even the extinction of species that depend on longitudinal movements along the stream continuum. Further, he lists, habitat loss or alteration, discharge modifications, changes in water quality and temperature, increased predation pressure as well as delays in migration as significant issues, all affecting the fish resource.
Larinier, M. (2001). Environmental issues, dams and fish migration. In: Dams, fish and fisheries. Edited by G. Marmulla. FAO Fisheries. Technical Paper 419. 166.
Lessard, J.L. and Hayes, D.B. (2003). Effects of elevated water temperature on fish and macroinvertebrate communities below small dams. River Research & Applications19: 721–732.
Stanford, J.A. and Ward, J.V. (1979). Stream regulation in North America. In: Ward JV, Stanford JA (eds) The Ecology of Regulated Rivers. Plenum Press, New York. 215–236.
Dr. Dhyal Singh
Department of Zoology
Uttaranchal College of Bio-Medical Sciences and Hospital