Roodeplaat Dam is a concrete arch dam situated on the Pienaars River (also known along parts of its length as the Moretele River and Moreletta Spruit), a tributary of the Crocodile River, which flows northwards into the Limpopo River

Limpopo River

The Limpopo River rises in central southern Africa, and flows generally eastwards to the Indian Ocean. It is around long, with a drainage basin in size. Its mean annual discharge is 170 m³/s at its mouth...

. The dam is a warm monomictic

Monomictic

Monomictic lakes are holomictic lakes that mix from top to bottom during one mixing period each year. Monomictic lakes may be subdivided into Cold and Warm types.-Cold monomictic lakes:...

 impoundment with stable thermal stratification during the summer.

Use

Roodeplaat Dam was originally an irrigation dam, and soon became popular for recreation. Later it became an important source for Magalies Water, a state-owned water board that supplies potable water to a large area north of Pretoria.

Water quality

Roodeplaat Dam's catchment contains a large part of the rapidly expanding City of Tshwane, which includes Pretoria

Pretoria

Pretoria is a city located in the northern part of Gauteng Province, South Africa. It is one of the country's three capital cities, serving as the executive and de facto national capital; the others are Cape Town, the legislative capital, and Bloemfontein, the judicial capital.Pretoria is...

. Two sewage treatment works feed treated effluent to the dam, resulting in highly eutrophic conditions comparable with those experienced in Hartbeespoort Dam

Hartbeespoort Dam

Hartbeespoort Dam also known as Harties is a dam situated in the North West Province of South Africa . It lies in a valley to the south of the Magaliesberg mountain range and north of the Witwatersberg mountain range, about 35 kilometres west of Pretoria...

. These conditions were already apparent in the mid 1970s and have not improved. Consequences of eutrophication include blooms of algae

Algae

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

 and cyanobacteria, and dense mats of water hyacinth

Water hyacinth

The seven species of water hyacinth comprise the genus Eichhornia. Water hyacinth are a free-floating perennial aquatic plant native to tropical and sub-tropical South America. With broad, thick, glossy, ovate leaves, water hyacinth may rise above the surface of the water as much as 1 meter in...

 (Eichhornia crassipes

Eichhornia crassipes

Eichhornia crassipes, commonly known as Common Water Hyacinth, is an aquatic plant native to the Amazon basin, and is often considered a highly problematic invasive species outside its native range.-Ecology:...

).The Department of Water Affairs' Resource Quality Services directorate is housed on the banks of Roodeplaat Dam, near the wall. This section is responsible for national monitoring of the surface water resources of South Africa.

See also

• List of reservoirs and dams in South Africa