Adult hippos monitor the presence of tourists in canoes on the Black Volta River in Bui National Park. Dense riparian forest covers the south bank of the river. The park was established as a Wildlife Refuge Area from 1971 and was home to one of West Africa's eight hippo populations. More than 300 hippos were counted in the park prior to the construction of the Bui Hydroelectric Dam which began in 2008. Two photos. Bui National Park, 12 June, 2009.