A Geodetic Based Estimate of Groundwater Storage Variations in Balaka, Malawi

Abstract

Groundwater is the main source of water for domestic and agricultural purposes in rural areas in Malawi. Continued exploitation of the groundwater for domestic, agricultural, mining and other industrial purposes results in continued temporal changes in its levels. Understanding changes in Groundwater storage Capacity is crucial in development and improving livelihoods of peoples. Attempts to study groundwater storage have been made in Malawi. However, lack of groundwater data triggered by scarcity of ground observation facilities hampers water resource management efforts. In this paper, the Gravity Recovery and Climate Experiment (GRACE) supported by Global Land Data Assimilation System (GLDAS) has been used to determine variations in Terrestrial Water storage capacity levels, which combines surface moisture, groundwater, snow and canopy water, in Balaka district in Malawi over a period of ten years (2012-2022). Due to the fact that Balaka does not register any snowfall, only surface moisture anomaly was used to downscale terrestrial water storage anomaly to determine the groundwater storage level changes from 2012 to 2022. The GRACE-based groundwater storage anomalies revealed no significant changes in groundwater levels as an increasing trend of as low as 0.002mm/year was determined. Influencing factors for the increasing trend were not addressed in this paper. Nonetheless, the results of this paper can benefit effective management of groundwater resources and help to promote use of geodetic gravity data in water resource management.