WILGE RIVER: Hydrology and geohydrology

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HYDROLOGY

"This sub-catchment consists of the area drained by the Wilge River and its tributary stream, down to the point where the Wilge River joins the Olifants River immediately upstream of the Loskop Dam.  The Wilge River drains a relatively small area to the east of Pretoria and, primarily due to the continual release of water from the dolomite and limestone formations, the streams and rivers are all perennial.  Minor discharges of treated domestic effluent from Bronkhorstspruit and Cullinan supplement flows in the Wilge River ."   (Ref 2)

"The sub-catchment contains one relatively large water supply dam (Bronkhorstspruit Dam), which supplies domestic and industrial water to the town of Bronkhorstspruit , as well as irrigation water to the extensive areas of irrigation downstream of the dam.  In addition, the sub-catchment has numerous small farm dams that are used to trap runoff in seasonal channels and supply this water for livestock watering." (Ref 2)

GEOHYDROLOGY

"There are also a very large number of small wetlands located along almost every stream and river in this sub-catchment (Marneweck et al., 2001).  These are formed at the uphill side of protruding dolerite formations (typically dykes and sills) that dip gently to the south.  These dolerite formations act as impermeable barriers and water collects on their uphill sides, saturating the soils.  The downstream end of each wetland is usually marked by a dolerite exposure where the water reaches the ground surface and flows over the dolerite barrier.  This system of inter-connected wetlands provides an extremely important attenuation mechanism that ensures water is released throughout the year, thereby maintaining perennial stream and river flows in this sub-catchment."    (Ref 2)

References

"Ref 2" (www.mining.wits.ac.za/FinalReport-Section5.doc)

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