Abstract Several activities in the PLTA Koto Panjang Reservoir in Batu Bersurat, have provided organic and inorganic matter in to the waters, that increased phosphate concentrations and have influenced phytoplankton growth and chlorophyll-a concentrations in the waters. This research aims to understand the relationship between Total-P and Chloropyll-a in the PLTA Koto Panjang Reservoir in…