WATER QUALITY IMPACTS OF HYDROPOWER PROJECT OPERATION IN BHOTEKOSHI RIVER BASIN SINDHULPALCHOWK DISTRICT IN NEPAL
|Ramesh Prasad Bhatt1, Sanjay Nath Khanal1, Ramesh Kumar Maskey2
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This study examines the impacts to Bhotekoshi River due to construction of a hydropower system in it. Bhotekoshi is a snow fed River, which originates from Himalayas in Tibet and pass through Nepal and confluences to Saptakoshi River. A range of physical, chemical and bacteriological water quality parameters around the project were studied from three different period, 1995-during EIA study, 1998- monitoring period and 2010- this study. The 1995 study showed high levels of total coliform, large volume of suspended load, high turbidity and lower BOD. During construction period in 1998, there was decrease in turbidity, suspended solids, and substantial improvement in other chemical and biological parameters because of the controlled conditions. It recorded increased temperature, reduced hardness upstream to downstream, more acidic pH, dissolved oxygen ranging between 7.50 and 8.50 mg/L as well as very poor microbial quality. The 2010 study revealed that the water was moderately hard (mean range of 5-72 mg/L CaCO3), salty and neutral with mean pH of 7.98±0.852643. Conductivity, TDS, and the major ions varied with elevated levels in the rainy season. The higher range of mean temperature, natural pH, increasing magnitude of mean conductivity downstream of powerhouse and decreasing trend in upstream powerhouse, higher turbidity at dam and downstream powerhouse site and lower turbidity in other stations, reduced hardness from upstream to downstream, higher DO in dam site etc are the main attributes found out in 2010. Total coliform pollution found occurred in all sampling stations, which suggests that the river water is unsuitable for domestic use due to increasing upstream discharges, riverside settlements, and release of households waste into the river. The finding have revealed that the project operation enhanced the cumulative impacts on the river system and mitigation measures taken during construction did not helped much to maintain the river water quality.