Trophic Status of Lake Phewa and Kulekhani Reservoir, Nepal

Abstract

Eutrophication is one of the growing environmental concerns and is affecting and compromising freshwater bodies across the world making the trophic status assessment of water bodies crucial for their restoration and sustainable use. This paper describes the trophic status of Lake Phewa and Kulekhani Reservoir from Nepal. Sampling was conducted during October 2017 (post-monsoon), April 2018 (Pre-monsoon), July 2018 (Monsoon) and February 2019 (Winter). Trophic State Index (TSI) as given by Carlson (1977) and Trophic State Index Deviation given by Carlson (1991) were estimated to assess trophic status and deviations between the Trophic State Indices. One-way analysis of variance showed significant seasonal variation (p < 0.05) in Secchi depth, total phosphorus (TP), TSI in both the water bodies. Both the water bodies were classified as eutrophic during pre-monsoon and post-monsoon, and hypereutrophic during the monsoon indicating the increased flow of allochthonous inputs from their respective catchments. Non-algal turbidity was found to be the limiting factor for productivity. There is a need for sustainable watershed management in order to reduce the nutrients runoff and accumulation in the water bodies.