Sustainable management scenarios for northern Africa’s fossil aquifer systems

Abstract

Achieving sustainability for the groundwater resources is more crucial and challenging in northern Africa than in any other part of the globe. We integrated temporal (April 2002–September 2019) terrestrial water storage (TWS) data derived from the Gravity Recovery and Climate Experiment (GRACE; April 2002–June 2017) and GRACE-Follow On (GRACE-FO; June 2018–present) missions with soil moisture, altimetry, and rainfall remote-sensing products to assess the sustainability of groundwater resources in northern Africa’s largest fossil aquifer systems: the Nubian Sandstone Aquifer System (NSAS) and the Northwestern Saharan Aquifer System (NWSAS). Results indicate the following: (1) in Algeria, Libya, and Tunisia, the NWSAS is currently being depleted due to excessive groundwater extraction; sustainable groundwater utilization could be achieved there if the average annual groundwater withdrawal is reduced by 2.70 km3; (2)the NSAS in Egypt (Dakhla sub-basin) is experiencing groundwater depletion, but it could achieve sustainable groundwater utilization if average annual groundwater withdrawal is reduced by 1.50 km3; and (3) the entire NSAS, in Egypt, Libya, Chad, and Sudan; the northern Sudan sub-basin in northern Sudan; and the Kufra sub-basin in Libya, northeastern Chad, and northwestern Sudan are healthy, and all three of them can be sustained at current levels of utilization. This study promises to improve our understanding of northern Africa’s aquifer dynamics and sustainability, signals an urgent need for integrated responses to develop sustainable utilization plans for groundwater resources, and promotes expanded and improved usage of GRACE and GRACE-FO products by the scientific community, end-users, and decision makers around the globe.