At the top of the Gamtoos Valley one would find the Kouga Dam, one of Port Elizabeth's three main water supply dams. The Kouga Dam was the first double arch dam to be built in South Africa. Other than for urban use, the dam is also the main supplier of irrigation water to the Gamtoos Valley. The pic was taken a little while ago when the dam last overflowed.
More information on the dam can be found here.