Final Environmental Impact Assessment Report for the Proposed Pumped Storage Power Generation Facility in the Steelpoort area, Limpopo and Mpumalanga Provinces 5. GENERAL DESCRIPTION OF THE AFFECTED ENVIRONMENT 5.1 Location and Topography The preferred site is located in the Limpopo Province on the eastern escarpment of the Nebo Plateau, to the west of the Steelpoort River and is situated within the Elias Motsoaledi Local Municipality, on the farms of Keerom 151 JS and Luiperhoek 149 JS. In addition, the extended route alternatives traverse the Mpumalanga Province. There is a difference in elevation of approximately 600m between the upper and lower reservoir sites. 5.2 Land Use The study area is largely rural in nature with rolling hills and valleys. The main land use features in the study area include agriculture (mainly in the form of citrus, vegetables and maize), low industrial development, various mining activities, residential areas and tourism. 5.3 Climate 5.3.1 Precipitation and Evaporation Data Rainfall patterns in the area are typical of the eastern half of South Africa, with the highest rainfall occurring during the summer months (October to March). Annual rainfall for the area is approximately 878mm, with the highest 24-hour rainfall occurring in December. The study area comprises various properties, which are situated within the lower parts of the B41C Quaternary Catchment as well as within the middle to lower parts of the B41D Quaternary Catchment. The B41C Quaternary Catchment receives an annual average rainfall of 694 mm, the majority of which falls during the months of October to March, according to the Surface Water Resources of South Africa Report (Water Research Commission 1990 ). The month of January has the highest average monthly rainfall of 123.1 mm. Mean annual evaporation for the region is 1500 mm. Frost occurs yearly for an average duration of 25 days per year, normally between May and September, but frost may occur as early as March and as late as October (Soil and Irrigation Research Institute, 1987). 5.3.2 Temperature The average monthly temperatures for the region are provided in Table 5.1 below. The average maximum and minimum temperatures for the region are 20.3 degrees General Description of the Affected 5-1 22/06/2007 Environment Final Environmental Impact Assessment Report for the Proposed Pumped Storage Power Generation Facility in the Steelpoort area, Limpopo and Mpumalanga Provinces Celsius and 7.3 degrees Celsius, respectively. The area generally experiences warm summers and cold winters. Table 5.1 Average monthly temperatures for the region (in degrees Celsius). Month T max T min January 23 12 February 22 12 March 22 11 April 20 8 May 18 4 June 15 1 July 16 1 August 18 3 September 22 6 October 22 8 November 22 10 December 23 11 Reference: South African Weather Services, 2006. 5.4 Geology The rocks in the area fall within the Bushveld Igneous Complex and comprise felsic rocks of the Rashoop Granophyre Suite overlying the mafic rocks of the Upper and Main Zones of the Rustenburg Layered Suite. The high plateau is underlain by granophyre in the south of the area and by mixed granite and granophyre in the north. These felsic rocks are several hundred metres thick and form the steep scarp slopes. Below the bottom of the scarp at the base of the felsic rocks is a leptite formation approximately 250m thick, dipping approximately 10 degrees westwards into the slope. This is in turn underlain by diorite beneath the pediment slope, grading into olivine-bearing diorite and gabbro beneath the valley floor. These mafic rocks underlying the leptite formation contain bands of anorthosite and magnetite, and all of the horizons dip around 10 degrees towards the west. All of the rocks discussed above have been intruded by dolerite/lamprophyre dykes, generally trending northeast (roughly parallel to the Steelpoort fault) and west of northwest (roughly perpendicular to the fault). 5.5 Soils and Agricultural Potential The soils that occur in the study area can be divided into three broad classes. These are summarised in Table 5.2 below. General Description of the Affected 5-2 22/06/2007 Environment Final Environmental Impact Assessment Report for the Proposed Pumped Storage Power Generation Facility in the Steelpoort area, Limpopo and Mpumalanga Provinces Table 5.2 Soil types in the study area Soil Depth General Agricultural Unit (mm) Characteristics Potential Ms 50-350 Brown to reddish-brown, structureless, sandy Low loam to sandy clay loam topsoil, often stony, on hard (occasionally weathering) rock. Rock outcrops occur in many parts of the map unit. Mainly soils of the Mispah (Ms) or Hutton (Hu, shallow phase) form. Sw 400-1200 Brown to reddish-brown, structureless, sandy Low to clay loam topsoil on brown to reddish-brown, moderate moderately structured, sandy clay loam to clay loam (occasionally calcareous) subsoil on rock. Occasional rock outcrops occur. Mainly soils of the Swartland (Sw), Valsrivier (Va) or Glenrosa (Gs) form. Oa 600- Brown to reddish-brown, structureless, sandy Moderate 1200+ loam to sandy clay loam topsoil on brown to reddish-brown, structureless to weakly structured, sandy clay loam, occasionally calcareous subsoil. Occurs close to stream channels. Mainly soils of the Oakleaf (Oa) form. Most of the upper and lower reservoir sites consist of shallow soils (Ms map unit), often rocky, either on the flat terrain on top of the escarpment or on the lower slopes. Close to the streams, a zone of deeper, alluvial soils occurs (Oa map unit), but this is usually no more than 100-150 m wide, and often slopes steeply down to the stream in places. In the east of the lower reservoir site, some deeper, but more structured soils occur (Sw map unit), with varying depth and rockiness. No areas of high agricultural potential are present in the study area. 5.6 Geohydrology, Surface Water and Drainage and Groundwater The study area comprises of various properties, which is located within the B41D Quaternary Catchment. The properties involved are Portion 1 of the farm Keerom 151 JS for the upper off-channel reservoir and Portions 1, 3, 4, 5 and 7 of the farm Luipershoek 149 JS for the lower reservoir. The following characteristics have been noted for the B41D Quartenary Catchment: • The general geology of these quaternary catchments comprises Bushveld Igneous Complex rocks and basic/mafic and ultramafic intrusives. • Soils in this region vary from moderate to deep sandy loam, with steep relief. • Vegetation for this area comprises of Savannah (Simplified Acocks Veld Types). General Description of the Affected 5-3 22/06/2007 Environment Final Environmental Impact Assessment Report for the Proposed Pumped Storage Power Generation Facility in the Steelpoort area, Limpopo and Mpumalanga Provinces 5.6.1 Geohydrology From a geohydrological perspective, the main points regarding the preferred site are as follows: Groundwater occurs typically in faults and shear zones. • The aquifer type is intergranular (i.e. weathered) and fractured. • The mean annual recharge is between 27-37 mm per annum. • The contribution of groundwater to the base flow of streams and rivers in the area is considered negligible. • The average depth to groundwater is between 10 and 20 m. • The harvest potential 1 for the Steelpoort area is seen to be between 10 000 and 15 000 m 3/km 2/annum. • The factor restricting the harvest potential of the groundwater in this area is the limited effective storage. Recharge occurs regularly during most years but cannot all be absorbed into the aquifer because of the low storage. The limiting factor is how much groundwater can be stored in the wet season to bridge abstraction during the drier season. 5.6.2 Surface Water Quantity • Catchment boundaries The study area is located within the Steelpoort River Catchment and its tributaries. The Steelpoort River Catchment drains into a northerly direction and eventually flows into the Olifants River. The boundaries of the catchment are occupied by some dense rural residential related activities, some small scale farming activities, as well as some game farming areas. • Mean Annual Run-off (MAR) Water Research Commission publications (Surface Water Resources of South Africa- Volume 1) were used to obtain the Mean Annual Run-Off (MAR) for each Quaternary drainage region. The B41B Quaternary Catchment has an estimated MAR of 17.8 x10 6 m3 per annum while the B41D Quaternary Catchment has an estimated MAR of 16.6 x10 6 m3 per annum. • Flood Peaks and Volumes Flood calculations were determined in the feasibility study. Water storage reservoirs were be classified according to Chapter 12 of the National Water Act, 1 The harvest potential is defined as “the maximum volume of groundwater that may annually be abstracted per surface area of an aquifer system to preserve a sustained abstraction”. General Description of the Affected 5-4 22/06/2007 Environment Final Environmental Impact Assessment Report for the Proposed Pumped Storage Power Generation Facility in the Steelpoort area, Limpopo and Mpumalanga Provinces 1998 (Act 36 of 1998) and relevant Government Notices, as dams with a Safety Risk. Social, economic, and environmental impacts were used during the classification process. Freeboard and spillway sizes will be determined according to the relevant SANCOLD (South African National Commission on Large Dams) publications. 5.7 Wetlands Under the National Water Act (No 36 of 1998), wetlands are termed as land that is transitional between terrestrial and aquatic systems, where the water table is usually at, or near the surface. It includes the land that is periodically covered with shallow water, and which land in normal circumstances would support vegetation typically adapted to life in saturated soil. Wetlands are classified as water resources, and as such are protected and should not be subject to any pollution or damage.