The reservoir provides a water supply to Lobatse, a town 70 kilometres (43 mi) south of Gaborone.

The Ngotwane then forms the border between Botswana and South Africa before flowing into the Gaborone Dam.

[7] Due to the hot, dry climate, about 2.3% of the stored water in Nnywane Dam is lost through evaporation in a typical year.

The reservoir was depleted in 1982 and the public water supply forced to shift to pumping groundwater.

[10] In June 2012, during an exceptionally dry winter, the dam fell to 52% capacity fill.