Theewaterskloof Dam. Dead trees on the banks of the Theewaterskloof Dam, Western Cape, South Africa. Seen here at approximately 30 percent capacity after a sustained drought in 2016. This earth-fill type dam lies on the Sonderend River. It was established in 1978 and forms a major component of the Western Cape Water Supply System. It mainly serves municipal and industrial use and irrigation purposes in the area.