Hirvikoski is situated by the Nurmonjoki River, which is a tributary (side river) of the Lapua River, which in turn flows into the Gulf of Bothnia at Uusikaarlepyy. The first hydro power facilities were built in the river in 1926 when Uusikaarlepyy Power Station was built. Several power stations were subsequently constructed, and the largest is Hirvikoski.
Like Oksava, a small-scale power station also owned by Vattenfall, Hinkua is situated by the Kalajoki River. The river is 130 kilometres long and flows through the central parts of Ostrobothnia Province, past Haapajärvi and down to the Bay of Bothnia. At Hinkua Hydro Power Station the head (drop) is 19.6 metres.
The most recent improvement of Hinkua was the refurbishment of automation and electrification as well as the renewal of turbine high-pressure hydraulic system in 2009.
In the past, the Kymijoki River was a border river between Sweden and Russia, and throughout history it has acted as a dividing line and a unifying stretch of water for the Kymenlaakso Region. The Kymijoki River is the largest river in southern Finland and it is popular thanks to its wealth of opportunities for fishing.