Seasonal variations in physico-chemical characteristics and water quality of Kosi River at Bhagalpur and Katihar District of North Bihar

The aim of this study is to assess physico-chemical characteristics, pollution studies from January 2017 to October 2017 of lower Kosi area. The range of various parameters of river water (The ambient temperature ranged between 17.2°C-32.4°C, water temperature 15°C-32°C, electrical conductivity 81–256 μS, depth 1–4 m total dissolved solids 41-130mg/l, pH 7.9–8.9, dissolved oxygen 8.8–16 mg/l, free carbon dioxide 4–60 mg/l, total alkalinity 14–26 mg/l, total hardness 32–158 mg/l, chlorides 1.9–9.9 mg/l, calcium hardness 60–140 mg/l, nitrate-nitrogen 0.017–0.117 mg/l, phosphate-phosphorus 0.11–0.2 mg/l, biochemical oxygen demand 0.4–4 mg/l, chemical oxygen demand 5.376–67.08 mg/l) exhibit seasonal fluctuations. Agricultural practices are performed both the side of river. This was due to allocthonous nutrients brought in to the river from the surrounding catchment area. The WQI at all sites III in pre-monsoon and winters at site II were in poor category. The above study indicated that the river water is slightly inclined towards eutrophication. Therefore, the conservation and management of this river water stretch is very much required.