Luangwa River ago, there was no way out and the Luangwa Rift filled with a Rift Valley Lake called the Madumabisa Lake, which rivalled Lake Malawi in size. The water of the lake overflowed in a river to the south-west, towards what is now the Kalahari, where it combined with the Okavango, Upper Zambezi, Cuando and Kafue rivers, emptying into the Limpopo River and flowing to the Indian Ocean. Several geological events combined to produce the current river systems. Faulting produced another graben just to the south of the Luangwa Rift, and running east-west: the Zambezi Rift Valley and the Chicoa Trough.
Duncan River was built the river served as the main navigation route into the valley, used by mining and logging industries. The route was navigable via Kootenay Lake as far as Bonner's Ferry, Idaho, on the Kootenai River. Duncan Dam was finished in 1967, the first of the three Canadian Columbia River Treaty dams to be built. Its purpose is to regulate flow into Kootenay Lake, in coordination with Libby Dam, to assure sufficient water flow for the Kootenay Canal and Corra Linn Dam projects. Duncan Dam does not produce any electricity. Duncan Lake, originally in length, is now long. Duncan River