Groundwater recharge in sub-humid drylands under different agricultural systems

Mudimbu, D.; Brauns, B.; Banda, K.; Lapworth, D. ORCID:; MacDonald, A. ORCID:; Namaona, W.; Owen, R.; Sinda, M.. 2023 Groundwater recharge in sub-humid drylands under different agricultural systems. [Lecture] In: The 50th Congress of the International Association of Hydrogeologists, Cape Town, South Africa, 17-22 Sep 2023. (Unpublished)

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Groundwater is a strategic long-term water resource used by an estimated 70% of the populations in sub-Saharan Africa for drinking, irrigation and a wide range of economic activities. Understanding groundwater recharge processes is key for effectively using and managing water resources. Very few studies have used direct groundwater observations to assess the impact of different farming systems on groundwater recharge processes. This study focused on assessing basement aquifer recharge in 4 instrumented catchments in Malawi (Chitedze), Zambia (Liempe and Kabeleka) and Zimbabwe (Domboshawa) within the SADC region between 2019-2022. Employing a range of methods, including direct field observations (groundwater hydrographs, precipitation data, stable isotopes, chloride mass balance and residence time tracer data), we quantify the amount of groundwater recharge as well as the timing and nature of recharge processes under both conservation and conventional tillage systems in these four study sites. Groundwater recharge was measured in most years across the study sites. The study reveals the strong climate controls on seasonal groundwater recharge volumes, the influence of low permeability layers in the unsaturated zone, and the likely magnitude of impact from different farming practices. Groundwater residence times are high (i.e. low fractions of modern recharge, interquartile range 1-5%, n=46), even in shallow piezometers, suggesting these unpumped systems may be highly stratified. The results provide an evidence-based suite of data that reveals much about key controls on groundwater recharge in basement aquifers in sub-humid drylands and will inform the development and management of such groundwater systems. Keywords: Groundwater recharge, basement aquifers, Southern Africa Development Community (SADC)

Item Type: Publication - Conference Item (Lecture)
Additional Keywords: IGRD, GroundwaterBGS, Groundwater
Date made live: 18 Dec 2023 14:00 +0 (UTC)

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