Batang Mahat River is one of the rivers which empties to PLTA Koto Panjang Dam. Batang Mahat estuary around PLTA Koto Panjang Dam is one of the fishing grounds. This study was aimed to obtain information about the water chemical and physical characteristics and biology (plankton) Batang Mahat around PLTA Koto Panjang Dam. This research was conducted in March-May 2019. The observation stations w…