ABOUT THE TALK The Vaal River Basin (VRB) is a key economic zone in the interior of South Africa; it is marked by intense mining, industrial, and agricultural activities. It experiences a predominantly semi-arid climate with an average annual rainfall of 570 mm. Population increase and the recurrence of drought places water supplies under pressure. Increasing groundwater use in the VRB as an alternative water source can reduce pressure on water supplies. The successful development and use of groundwater in the basin will largely depend on improved understanding of the groundwater system.
The purpose of the study was to quantify the groundwater storage and to assess the effects of both human and natural stressors on groundwater resources. Groundwater storage was estimated by subtracting soil moisture and surface water storage from the Grace Recovery and Climate Experiment (GRACE) based terrestrial water storage. The GRACE-based groundwater storage was estimated to be 39.72 km3 from 2003 to 2014 with an increase of 3.31 km3/year. The GRACE groundwater storage captures annual variability in water storage distribution. The GRACE groundwater storage also mimics the rainfall amount with a time lag of less than six months. The findings of the study shows that the GRACE-derived data is inapplicable for smaller catchment. The GRACE groundwater storage was not validated in the current study because of the sparsity of groundwater level data in the basin. This study demonstrates that the gravimetric data derived from the GRACE satellite provide an opportunity to assess groundwater storage changes in large basins (150 000 km2). The application of integrated approaches that involve space-based observations such as gravimetric data from the GRACE satellite and ground data to study groundwater systems in complex basins is of great value in data-scarce basins. The space-based observations are not a replacement of ground monitoring and collection of hydrological data, more effort must be directed to collecting and monitoring groundwater data to help understand how the quantity of groundwater is evolving in real time for better groundwater management.
ABOUT THE SPEAKER "Khuliso is a data-driven scientist; as a result, he enjoys getting his hands dirty and collecting data in the field. He has a strong passion for solving groundwater-related problems".