river rising in the Atacora massif in northwestern Benin. It is approximately 310 miles (500 km) in length and flows southward, where it is joined by its main affluent, the Okpara, on the left bank and by the Zou on the right. It then divides into two branches, the western one discharging into Lake Nokoué in the Niger Delta near Cotonou and the eastern into the Porto-Novo Lagoon. Rain forests grow along the shores; navigation, although impeded by rapids, is possible during the rainy season. The river's fish, including freshwater and processed, is exported to Nigeria and Togo. Millet, sweet potatoes, and yams are cultivated, and the Ouémé Valley development scheme has been undertaken to improve agriculture.