Gulf of Bothnia
The lake is a bifurcation lake: the main part of its waters flow into the Merikarvianjoki River that mouths into the Gulf of Bothnia in Merikarvia but part of the waters flow through the Salmusoja River into lake Poosjärvi that drains through the river Poosjoki – Lampinjoki – Pohjajoki into the Gulf of Bothnia in Ahlainen, Pori.