Impacts of hydropower on seasonal rhythms of diatoms in Indian Himalayan region

The hydrology of riverAlaknanda in the Indian Himalayan region having glacier at source varies due to magnitude of melt in different seasons. Power generation requirements cause abrupt perturbations in the discharge of serially impounded Alaknanda River. Diatom assemblages were recorded at eight stations within and outside hydroelectric project (HEP) area to study the seasonality in diatom assemblages during 2017-2018. The assemblages reflected the bare minimum of seasonality at each station viz. Achnanthidium pyrenaicum-Achnanthidium minutissimum during May and June of summer season at S3; A. pyrenaicum -Cymbella laevis during January and February of winter season at S4; late summer at S5 (A. pyrenaicum-C. placentula var. euglypta), S6 (A. minutissimum-A. pyrenaicum) and S8 (A. pyrenaicum A. minutissimum). The assemblages showcased no seasonal consistency during the study period. These were inferred as perturbations caused by discharges held and released for power generation, suggesting the unstable nature of communities in theAlaknanda River ecosystem impacted by serial impoundments.