Dam-Induced Alteration in Seasonal Fluvial Discharge Time Series in Kali Gandaki Hydropower Dam, Syangja, Nepal: An Application of Wavelet Analysis

Abstract

The construction of dams across rivers controls the magnitude of downstream floods and limits the suspended sediment transport into the downstream areas. We elucidated the downstream hydrological alterations compared to upstream after the construction of Kali Gandaki ‘A' hydropower dam, Sy-angja, Nepal using continuous wavelet analysis, cross wavelet analysis and wavelet coherence. The downstream fluvial flow in winter and pre-monsoon seasons showed highest water deficit condition compared to monsoon and post-monsoon seasons. The dam-induced changes in fluvial flow with decreasing amount of sediment alter the downstream flood morphological characteristics of river reach such as flood depth, wetted perimeter of river section, flow velocity, and maximum and minimum floods together with the decrease in amount of suspended sediment. The dam-induced downstream alterations directly or indirectly create stress on the aquatic as well as terrestrial ecosystems. The findings of this study will be useful for hydropower dam gates operation that fulfils the minimum ecological threshold.