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A Study on Change in Flow Regime and Discharge Impacts on Water Quality of Hydropower Operation

Ramesh Prasad Bhatt, Sanjya Nath Khanal


The main environmental effect on the river system for hydropower operations is the alteration of flow regime which affects the water quality and cause impact on aquatic ecosystem. Quantitative assessments of the critical components of the flow regime were obtained from hydrological survey and comparison of data’s from both historical (pre-impact) and recent (post-impact) times. Altogether, 75 parameter of water quality obtained from the laboratory analysis were used as variables inputs for Principal Components Analysis (PCA). The monthly and annual discharge rate of the river was found higher in previous periods. The test result show marked increase in temperature, pH, mean conductivity, turbidity at downstream, suspend solids and substantial increment in the physical and chemical qualities of river water in compression to upstream water quality of the river. The low DO content below dam site, decreasing total nitrogen in the downstream and high level of coliform 1.98x103 cells/100ml at confluence below wire site which is probably due to the discharge of domestic sewage from upstream settlements into the river and open defecation along the river banks. Change in flow regime found effects on macroinvertebrates (e.g. aquatic insects and micro-crustaceans), reduction in fish diversity, and its abundance.


Hydropower operation, flow regime, downstream effects, water quality impact, fish diversity

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