Lake Victoria is one source of the Nile and it provides major fisheries (which are important both to local livelihoods and the national economies), is a key transport route between three major countries of the East African community and the Lake outflow provides a major hydropower source. The lake is unusual in that it is the largest tropical lake in the world and is largely fed by on-lake rain (not rivers) and largely emptied through evaporation (not rivers). The evaporation and lake-land circulations mean the lake triggers rain over the lake at night, making it a unique coupled hydrological-meteorological system.