The need for managing historic groundwater in the Limpopo River Basin, southern Africa: based on the δ18O, δ2H and 14C data

Abstract

Groundwater is often considered as an archive for climate change records due to its link with precipitation. The isotopic signature in precipitation is controlled by factors such as temperature and season, where stable isotopes in groundwater retain the signature of the effects of physical changes at the time of recharge. 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. Temporal variation in stable isotopes and ambient temperature in relation to 14C data revealed the presence of evaporation effect on groundwater at different times due to long-term climatic variability in the basin. Evidence of variability in ambient temperature was recorded in geological times, with increasing trends in the Holocene and Late Pleistocene. Therefore, increasing water demand by various economic sectors requires planned intervention while using historic groundwater to achieve sustainable development.