A Geodetic-based Estimate of Groundwater Storage Variations in Balaka, Malawi

Abstract

Ground water is the main source of water for domestic and agricultural purposes in rural areas in Malawi. Continued exploitation of the ground water for domestic, agricultural, mining and other industrial purposes results in continued temporal changes in its levels. Understanding changes in the Groundwater Storage Capacity is crucial in development and in improving the livelihoods of people. Attempts to study groundwater storage have been made in Malawi. However, the 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-FO), supported by Global Land Data Assimilation System (GLDAS), has been used to determine variations in Terrestrial Water storage capacity levels, which combine the surface moisture, groundwater, snow and canopy water conditions in Balaka district, in Malawi, over a period of ten years (2012-2022). Owing to the fact that Balaka does not register any snowfall, only the surface moisture anomaly was considered in reducing the terrestrial water storage anomaly to determine the groundwater storage level changes from 2012 to 2022. Since an increasing trend, declining to levels as low as 0.002mm/year, was determined, the GRACE-based groundwater storage anomalies revealed no significant changes in groundwater levels. Influencing factors for the increasing trend were not addressed in this paper. Nonetheless, the results of this paper can contribute positively to the effective management of groundwater resources and promote the use of geodetic gravity data in water resource management.