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Title: Possible Impacts on Fish Dynamics Due to Implementation of Proposed III Trishuli Hydroelectric Project
Authors: Pathak, Janak Raj
Keywords: Hydropower;Electrical energy.;Fish Sampling
Issue Date: 2007
Publisher: Department of Environmental Science
Institute Name: Central Department of Environmental Science
Level: Masters
Abstract: Hydropower is a proven renewable resource of electrical energy. It is the cheapest, the cleanest and environment friendly source of energy a country can tap, if implemented properly.Despite of all these benefits and importance, the environmental constraintsarising as a result of hydroelectric projects cannot be eliminated in this 21 century where the whole world is taking pace towards eco-friendly sustainable development.Among these various environmental effects which evolve as a result of the implementation of hydroelectric project, the impacts on the life cycle of ichthy ofaunaare one of them. The construction of dams to divert water to the powerhouse causes serious effect on fisheries.The present study“Possible Impacts on Fish Dynamics due to Implementation of Proposed III Trishuli Hydroelectric Project”aims in determining the effects likely to be caused on the fish population due to the implementation of III Trishuli Hydroelectric Project. Third Trishuli Hydroelectric Project is a run-off the river type project located in Salang VDC and Benighat VDC of Dharding district in the Central Development Regions of Nepal. The river is a snow fed river from which a design discharge of 115.25 m /s will bediverted for power generation through a side intake on the right bank by constructing 8 mhigh concrete gravity dam across the river. The present research is the outcome of thestudy carried for 10 months starting from December 2005 to October 2006 and both thefield visits and desk study were done in this period of time.The present study revealed 16 species of fishes in an around the proposed project area i.e.from the confluence of Malekhu Khola and Trishuli River to the confluence of ThopalKhola and Trishuli River of about 7 km length. Among these identified fish species Neolissochilus hexagonolepis, Tor putitora and Schizothoraichthys progastus havebeenquoted vulnerable in the National Red Data Book. Similarly, among these captured species;Tor putitorais long distance migrant,Labeo dero, Schizothoraichthys progastus,Garra annandalei, Glyptothorax sps., Lepidocephalus guntea, Barilius barila,Aspidoparia jaya, Neolissochilus hexagonolepis andBarilius barnaare mid-migratoryand the rest of others Channa orientalis, Crossocheilus latius, Schistura beavani, Puntiussarana, Nemacheilus coricaandBotia almorhae are resident or local migrant fishes.Present analysis of physical, chemical and biological parameters of water from two sections i.e. intake and powerhouse indicate that water is suitable for fish development. st 3 The concept of obstruction to migration is often associated with the height of the dam.The proposed concrete hydroelectric dam which is about 8m high blocks the entire path of migratory fishes unless and until some mitigative ways or fish passes has not been installed across the dam.CPU analysis indicate that population density of fishes are higher at the confluence of the rivers than elsewhere. Construction of dam near these sitescan have substantial effect on fish community.The reduced flow of water downstream the dam decreases the spawning ground and availability of food supply.The release of 10% of the minimum mean monthly flow i.e.6.2 m 3 /s water can augment to reduce such problems in the dewater zone to some extenthowever the habitat cannot be restored to its original state. Channelization of water anddepositing gravels to create pools to increase spawning habitat can be effective in gettingoptimum result. In addition to problems relating to fish passage at obstacles, there are indirect effects of dams which may prove of major significance such as changes in flow,water quality, the increase in predation and drastic changes to the habitat upstream ordown stream.Most of the local fishermen, now take agriculture as their main occupation and they don’t have clear vision about the effects of dam on fisheries. Sahani people arethe migratory fishermen group from Terai Region. Impacts to these people can beeliminated for they can move to other regions if the fishing problems are serious. Certainun welcome situations arising during the construction and operation of the reservoir have interactive, negative influences on ecology and environment. Thus appropriate precautionary measures should be adopted during construction and operation of the project so that there is minimum impact on fish community in the existing habitat.
Appears in Collections:Environmental Science

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