The Rietvlei Nature Reserve developed out of the Rietvlei Water Scheme. The scheme is responsible for conserving the catchment area and accumulating and distributing water. The Rietvlei Dam, built during the Great Depression and completed in 1934, lies in the Sesmylspruit and is supported by the Marais Dam, which acts as sludge dam for the larger Rietvlei Dam.

The dam wall as well as all the other brickwork was built entirely by hand. During those difficult years of the Great Depression, manual labourers were only too happy to work for four shillings a month. All the soil was carted away by mule carts, evidence of which are the numerous horseshoes still found on the koppie across the yacht club. During a two-year programme started in 1988, the dam wall was raised and other improvements were made.

Apart from water from the Sesmylspruit, water comes into the dam from four fountains on the reserve, one fountain on an adjacent property and five boreholes on the reserve. Today, Rietvlei Dam provides in 15% of Tshwane's water requirements.

Since acquiring the dam in 1929, the City Council of Pretoria never opened the property to the public. It nevertheless planned the reserve on ecologically sound principles and introduced game to the area, a factor which contributed to the proclamation of the nature reserve. The reserve covers an area of 3 800 ha, is 1 525 m above sea level and has the capacity to support 1 500 to 2 000 head of game.

Some of the historical sites on the reserve are the old farmhouse, an entrenchment of loose stones constructed by the British forces during the first occupation of Pretoria and two groups of graves on which the epitaphs are still visible.

The Rietvlei Dam and Nature Reserve offer a variety of activities and sporting facilities. A yacht clubhouse was built on the north-western shore of the dam while an angling area is situated on the northern and western shores. Because Rietvlei Dam is such an important source of water for Tshwane and the surrounding area is a proclaimed nature reserve, no motorboats are allowed on the dam.

A trained conservationist manages the reserve on sound nature conservation principles. The roads have been well planned for use in game viewing, patrolling, maintenance and firefighting. The roads divide the reserve into 31 blocks. The veld is conserved by rotation grazing, with blocks being routinely burnt and licks put out as supplementary feeding for game.

The reserve has a typical highveld climate, receives an average of 724 mm rain during summer and has dry winters with frost. Veld on the reserve is the central variety of Bankenveld and the terrain is made up of open grassland with undulating hills.

The wetlands of the reserve are a rare asset. Indigenous trees, typical of the highveld, are clustered in small groups. In areas where trees do not grow, shale formations are conspicuous. Because of farming practices before the reserve was proclaimed, several exotic species entered the area. Infiltrators such as Acacia dealbata, or the silver wattle, cause the most problems. Imported from Australia, this wattle flourishes in the reserve because it has no natural enemies. The seed can lie in the soil for 50 years and still germinate. The wattles are taken out mechanically and the wood is used as fuel.

The main geological formation is lava, extending in a broad band from north to south in the reserve. The soil is therefore heavy red loam, which supports good grazing veld. Belts on both sides of the lava have broken down into greyish loam. The eastern part of the reserve has dolomite covered by a sill of chert and sandy loam. Altogether 147 varieties of herbs grow among the 78 species of grass. During a good year, 200 kg of grass and 1 300 kg of herbs (dry weight) are produced on one hectare. Grassland is a dynamic ecosystem continuously changing composition under the influence of grazing, fire, rain and drought.