Abstract
The Olifants River basin continues to be one of the most important river basins in South Africa. The basin is home to both small and large scale mining industries, and commercial as well as small holder agricultural farms that use a lot of water for irrigation. Most of these activities are located in the upper middle catchment (UMC) of this basin. The basin produces coal that is used as a source of energy to the 11 ESKOM (The power utility of South Africa) coal-fired power stations, eight of which are within the basin. These eight power stations produce approximately 70% of South Africa’s electricity. The Olifants River basin thus plays a key strategic role in the national economy of South Africa and is, therefore, a very important river basin in as far as the economy of South Africa is concerned. Water is at the centre of these economic developments. Unfortunately, climate change is likely to severely affect the water resources due to changes in spatio-temporal distribution of precipitation and evapotranspiration. In spite of the uncertainties about the precise magnitude of climate change, particularly at local scale, measures must be taken to anticipate, mitigate and/or adapt to its adverse effects on water resources availability. Therefore, an attempt was made in this study to assess the impact of future climate change on groundwater recharge in the UMC of the Olifants River basin. The assessment was done using the Soil and Water Assessment Tool (SWAT) model with climate and hydrological data obtained from different sources as inputs. The study was based on two representative concentration pathways scenarios, the RCP4.5 and RCP8.5 scenarios. The study itself involved building four sets of input data to the SWAT model representing each climate change projections. These projections were: the recent past period (1960 -2010), current time period (2011 - 2020), mid-term period (2021 - 2050), and long-term period (2051 - 2100). The SWAT model was run for each of these climate change projections to obtain the magnitude and spatio-temporal distribution of groundwater recharge in the UMC. The results show that the UMC is receiving a total recharge of 120.6 mm per annum under the RCP4.5 scenario, and 174.3 mm of recharge under the RCP8.5 scenario. However, the average annual recharge that the UMC has been receiving in the recent past is 121.5 mm under the RCP 4.5 scenario, while under the RCP8.5 scenario, the annual recharge has been 119.1 mm...
Ph.D. (Civil Engineering)