Historic Climatic Variability and Change: The Importance of Managing Holocene and Late Pleistocene Groundwater in the Limpopo River Basin, Southern Africa

The isotopic signature in local precipitation is driven by factors that control fractionation such as temperature and season, where stable isotopes in groundwater retain the signature of the effects of physical changes at the time of recharge. High ambient temperature and decrease in rainfalls are characteristic features of the El Nino event in southern Africa that has resulted in tremendous pressure on water resource management. Based on the environmental isotope records from the Limpopo River Basin in South Africa and Botswana, this study determines ambient temperature during rainfall at the time of recharge and correlates it with the 14C Mean Residence Time to observe temperature variability in the Holocene and Late Pleistocene. Its implication for the need to manage such historic groundwater is discussed. Temporal variation in stable isotopes and ambient temperature in relation to 14C data revealed the presence of evaporation and recharge at different times due to long-term climatic variability in the areas located within the arid and semi- arid climatic settings in the basin. Evidence of variability in ambient temperature was found in geological times, with increasing trends in the Holocene and Late Pleistocene. Therefore, increasing water demand by various economic sectors requires planned intervention in groundwater resource management to achieve sustainable development.