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The Berg Catchment Groundwater Reserve

In February 2022, Umvoto was commissioned by the Department of Water and Sanitation (DWS) Chief Directorate: Water Ecosystems Management (CD: WEM) to conduct a high confidence groundwater Reserve determination study for the Berg catchment (hereafter referred to as the ‘Berg Reserve Study’).  

The Berg catchment study area, located in the southwestern corner of South Africa, falls entirely in the Western Cape Province and covers a total area of roughly 13 000 km2. It borders the Olifants/Doring Water Management Area (WMA) to the north and the Breede-Gouritz WMA to the east. The catchment experiences a Mediterranean climate and receives most of its rainfall in winter. There is a large spatial variability in mean annual temperature and precipitation across the study area due to the varying topography from low lying coastal plains (in the northwestern part of the catchment) to high mountain ranges along its eastern edge. 

The Berg River catchment (also known as the Great Berg River) forms the largest surface water catchment in the former Berg WMA, which also includes other smaller catchments such as the Diep, Kuils, Eerste, Sir Lowry’s and Steenbras River catchments. The study area contains 22 estuary systems including the Berg River Estuary Ramsar Site and Langebaan Lagoon, both of which receive contributions from groundwater. Several significant wetlands are of importance in the Berg catchment, namely the Edith Stevens Wetland Park, Zeekoevlei and Rondevlei (both of which are part of the False Bay Nature Reserve Ramsar Site), Zoarvlei and Rietvlei. 

Geologically, the majority of the Berg catchment is underlain by the Klipheuwel and Malmesbury Groups which are comprised of argillaceous rock types, typically greywackes and shales. These basement rocks have been intruded by the Cape Granite Suite which mainly occur as plutons, such as Paarl, Perdeberg and Darling. Thereafter, a long period of uplift and erosion resulted in the deposition of sandstones which form the Table Mountain Group (TMG), particularly the Peninsula and Skurweberg formations that form the escarpments due to erosion resistant quartzites. These formations form deep fractured rock aquifers (Peninsula and Nardouw Aquifers) that are often confined and high yielding with good water quality. Sediments that eroded from these formations (particularly from the softer Malmesbury Group) were deposited in the western and coastal portion of the catchment to form the Bredasdorp Group, Sandveld Group and Quaternary age deposits. These sand deposits form major primary sedimentary aquifers which can be extremely high yielding but are vulnerable to contamination due to their unconfined nature and high infiltration rates. 

Map of berg river reserve
Locality (right) and geological (top left) maps showing the extent of Berg catchment. A broader study area extent was considered to ensure that all Groundwater Resource Units (GRUs) are adequately evaluated. Infrastructure map (bottom left) showing various dams and bulk water supply infrastructure of the Western Cape Water Supply System (WCWSS).


Reserve Determination

The Reserve (i.e., the water “set aside” to provide for BHN and to sustain water ecosystems) is the only right to water in the National Water Act (NWA; No. 36 of 1998). It therefore has priority over all other water use and should be set as soon as the ‘Class’ is determined for each water resource. This is to say that the amount of water required for the Reserve must be met before water resources can be allocated to other water users. It is important to note that the NWA clearly includes ‘groundwater’ in the definition of a “water resource” but the overall characteristics of groundwater sometimes require a different or integrated management approach. 

The procedure for determination of the groundwater contribution to the Reserve follows the stepwise process outlined in the NWA and associated Resource Directed Measures (RDM) Manuals. The procedure is divided into eight steps and is inter-linked with the Water Resource Classification System (WRCS). The WRCS is a process by which water resources are categorized into Water Resource Classes (WRCs) that account for the ecological, social and economic factors that are dependent on the water resource. 

Diagram showing reserve determination
The 8-step procedure for determining the groundwater Reserve and its alignment with the 7-step Water Resource Classification procedure as defined by Regulation 2(4) of the NWA (No. 36 of 1998). 

The Groundwater Reserve  

Due to the increasing number of water use licence applications (WULAs) in the study area, the associated impacts that proposed developments may have on the availability or quality of water, the conservation status of various resources, and the complexity of geological and hydrogeological characteristics within the Berg catchment make it increasingly impossible to assess WULAs using a low confidence desktop-based determination of the groundwater contribution to the Reserve. 

The CD: WEM has therefore initiated the Berg Reserve Study which will assist the DWS in making sound management decisions regarding stressed or over-utilised water resources, while ensuring that they are afforded a level of protection that will assure a sustainable level of utilisation in the future. This ongoing study will determine groundwater contribution to the Reserve, in terms of both groundwater quantity and quality, to satisfy the basic human needs (BHN) and to protect aquatic ecosystems in priority water resources. Detailed determinations aim to produce high-confidence results (based on site-specific data collected by Umvoto specialists) that will be used for all compulsory licensing exercises, as well as for the individual licence applications that could have a large impact on any catchment, or a relatively small impact on ecologically important and sensitive catchments. 

The Progress to Date 

The Berg Reserve Study is set to be completed by February 2024. To date (December 2022), Umvoto has completed Phase I (Inception) and Phase II Water Resource Information and Data Review) of the project deliverables and are currently in Phase III (Reserve Determination). Study deliverables are readily available for the public and can be found here.  

The outcomes of this study will influence the overall management procedures of the water resources in the area and may eventually impact you or your organization as a water user. Stricter controls on groundwater may be implemented and could have bearing on future water use in the area. These controls are geared towards sustainable management of the water resource which influences all water users and aquatic ecosystems. 


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