The Songwe sub-basin forms the eastern part of the Lake Rukwa Basin and extends over an area of about 10,800 km2 covering parts of Chunya, Mbeya DC, Mbeya Urban, Songwe District, Mbozi, Mbarali, and Rungwe District. The sub-basin population is about 843,278 (2012 National Census) 40% of whom live in Mbeya City and the surrounding peri-urban areas. Other urban areas include the small towns of Mbalizi, Mlowo, Songwe and Chunya. The sub-basin has an average population growth rate of 2.9% which is comparable to the Tanzania national average. The sub basin population is projected to grow to about 1,643,629 by 2035, a 95% increase.