Hartbeespoort Dam - spectacular view with all ten sluices open.

All ten sluices open at Hartbeespoort Dam. Aerial photography as never seen before.

In 1906, the government ordered a public inquiry into the feasibility of building an irrigation dam in the Hartbeespoort of the Magaliesberg. The engineer of the Department of Irrigation that led the inquiry, submitted a favourable report to the government and the Hartebeestpoort Act. 32 of 1914 was accepted by Parliament. As early as 1909 there were test holes drilled at the bottom of the river to determine whether the rock formation was suitable for building such a huge dam. The size of the catchment area was calculated, the water flow was measured and estimates made of the potentially irrigable land. Downstream claims to the existing water stream were established. The topography of the riverbank and rock formations were examined to evaluate the viability of the port for the construction project.

The construction of the dam officially started in August 1916. Initially, work was delayed pending a court judgment with General Hendrik Schoeman and a certain Mr. Marshevin about the expropriation of their properties. The dispute was later resolved but discontent remained after a hastily passed law to facilitate the expropriation. In his book "Agter die Magalies", Bertus de Beer argues that the government acted in a heavy-handed manner to resolve a number of issues surrounding the construction of the dam. Mother Nature caused further delays due to flooding. In 1914 and again in 1918, huge amounts of construction wood washed down the river and were never recovered. During 1915, the wall of the Geldenhuysdam further up the river broke and the flooding of the site also caused a delay.

The disruption caused by the First World War, and the complications brought on by the Rebellion of a group of Afrikaners, brought further delays to the building. Then the first company was liquidated due to financial losses resulting from the floods and delays. In 1921 a second company took on the project and appointed an engineer, F. W. Scott, who tackled the project with renewed energy. In April 1923, after all the setbacks and political upheaval, the project was completed. In September of that same year the road over the wall of the Dam and through the tunnel was opened to traffic. The dam first overflowed in March 1925.

The dam was built on the farm Hartebeestpoort, once owned by the Boer General Hendrik Schoeman (1840–1901). The farm and adjacent land were acquired by the State, mainly through the facilitation of his son, Johan Schoeman (1887–1967), around 1912. The completion of the dam made the agricultural land north of the Magaliesberg much more valuable, especially land close to canals and the Krokodil River.

The dam wall is 149.5 metres long and 59.4 metres high, built across a gorge cutting through the Magaliesberg. The reservoir is fed by the waters of the Crocodile River and Magalies River and covers approximately 18.83 square kilometres, with a mean depth of 9.6 metres and maximum depth of 45.1 metres. It has a surface area of 20 square kilometres, and its normal range of annual water level fluctuation is 0.8 metres. The mixing type of the reservoir is monomictic.

A single-laned, tarmac road skirts the water's edge on the north side; along its route it passes through a 56.6 m long tunnel and also crosses the dam wall.

Hartbeespoort Dam supplies irrigation water through a 544 kilometres long network of canals to 159.76 square kilometres of farmland on which tobacco, wheat, lucerne, fruit and flowers are produced. Deteriorating water quality, most notably Microcystin toxin, is now causing much of the irrigated agriculture to fall into disuse.

Hartbeespoort has become a very popular holiday and weekend resort for the inhabitants of Johannesburg and Pretoria; it is the principal water recreation area of northern Gauteng and many types of water sports are enjoyed on the dam. The Transvaal Yacht Club has been operating at the dam since its construction in 1923.