lake, part of the Congo River basin, northwestern Congo (Kinshasa). Lake Tumba lies 75 miles (120 km) northwest of Lake Mai-Ndombe (formerly Lake Léopold II). It covers 190 square miles (500 square km) and is 6–20 feet (2–6 m) deep. The lake empties into the Congo River by Irebu channel, just opposite its confluence with the Ubangi River. Lake Tumba is shallow, with low shores, and is navigable by river steamer.