If the 81 metre high De Hoop dam is constructed on the Steelpoort River, "there is some risk of losing unknown biodiversity". The area where the dam is due to be constructed is "one of the areas in the country where the most new species are being discovered" and "probably the single area in the country where botanical conservation is the most important for preventing loss of unknown genetic resources".
It is known to contain at least 20 species of unique endemic plants. These species, including plants with medicinal properties, will be flooded if the dam is built. Some of the plant species have yet to be officially described by scientists. This is reported in the draft environmental impact assessment for the Olifants River Water Resources Development Project (ORWRDP).
In mitigation of this, the summary report suggests that "an area of Sekhukhune Mountain Bushveld, similar in size to the proposed development, be formally conserved." Plant species could also be rescued before the flooding and relocated. The EI process found that at least 20 Red Data species that are already threatened with extinction occur in the area. One of these is the barred minnow, which will become locally extinct if the dam is built.
The dam, which will be as tall as a 21-storey building, is intended to supply water for some of the poorest people in the country, as well as for future mining developments in the area. A 300km network of water pipelines and reservoirs will distribute the water. The Steelpoort is the last major tributary of the Olifants River that does not have a large dam on it.
The proposed De Hoop dam will be able to store 347 million cubic metres of water and cover an area of about 1690ha. In comparison, the Flag Boshielo Dam on the Olifants River (when the raising of the dam wall is complete) can hold 184 million m3. One innovation of the dam will be that water released from the dam will be mixed from different levels, to ensure that river life downstream is not harmed by water that is too cold or oxygendeficient.
This is a problem that older dams do not address. The dam will also be able to output more water at a time than older dams, in order to meet the ecological needs of the river. The EI report concludes that these releases may have a positive effect downstream, as the flow of the river will be more regular in drier periods.
The dam is expected to have "little influence" on flows downstream in the Olifants River, such as the Kruger National Park. If constructed, the dam will flood a section of the R555 provincial road, which will have to be re-routed. The EI report determined that the best route for the new road would be on the western side of the dam.
The De Hoop Dam is projected to be completed by 2009 if the authorities decide that the project must go ahead. Construction of the dam and related infrastructure is expected to be fast-tracked, and between 600 and 800 jobs should be created, with 60 percent going to local people.
Job creation will also come from mineral resources in the area which are projected to sustain mining for 100 years. Municipalities in the area need to be capacitated to keep up with this projected development.
The environment impact assessment concludes that water resources in the Olifants River catchments are scarce, and that they should be used sustainably. It tasks the Department of Water Affairs and Forestry with ensuring that this occurs.