Water–Isotope Capacity Building and Demonstration in a Developing World Context: Isotopic Baseline and Conceptualization of a Lake Malawi Catchment

Abstract

Developing countries such as Malawi require improved access to isotope tracer tools to better characterize and manage water resources threatened by land development, deforestation and climate change. This is the first published study to use an isotope facility developed in Malawi for this purpose, instead of relying upon sample analyses from abroad. Results from this new facility are used to evaluate an important Lake Malawi catchment in the Rift Valley. This work successfully established a stable-isotope baseline, hydrochemical signatures, and system conceptualization against which future policy change and management strategies may be measured. Precipitation isotopic composition was consistent with the Global Meteoric Water Line, but varied, confirming different precipitation systems nationally. Groundwater largely followed a Local Meteoric Water Line, with limited isotopic variation indicating predominant areal groundwater recharge, but with dry-season evaporative enrichment of groundwater near Lake Malawi. Surface-water isotopes widely varied with local precipitation, suggesting the latter accounted for wet-season river flows, but upstream dambo (complex wetlands occupying a shallow, seasonal waterlogged depression) helped sustain dry-season flows. Isotope capacity reinforced water-resource conceptualization and provenance in a hydrologically complex, but not atypical, Rift Valley system, exhibiting a noted complexity of groundwater–surface-water interactions. The latter, critical to integrated water resource management, requires more focused study, to which an expanded array of isotopes will contribute to tracking Sustainable Development Goal 6 targets. This study and future catchment studies should help underpin Malawian water-resource policy implementation on several identified fronts.

True 2-D Resistivity Imaging from Vertical Electrical Soundings to Support More Sustainable Rural Water Supply Borehole Siting in Malawi

“…This study contributes to the Climate Justice Fund (CJF) Water Futures Programme of research, funded by the Scottish Government, that aims to assist the Government of Malawi in achieving SDG 6 (www.cjfwaterfuturesprogramme.com). CJF is led by the University of Strathclyde and provides local-to-national scale coverage across a broad range of water resource issues [5,6,[60][61][62]. The field demonstration phase of this study was implemented within a CJF geographic focus area that covers most of the Traditional Authority (TA) of Mazengera located the Lilongwe District of Central Malawi (Figure 1).…”

“…Streamflow experiences marked seasonal variations, with many smaller rivers and streams dry during winter. Possible changes in some reaches may occur across the plateau from gaining to losing conditions where river flows become influent to groundwater [14,15,60]. Biological contamination (e.g., by faecal bacterium, Escherichia coli) of surface water is common.…”

“…The Basement hosts aquifers that correspond to the classical concept of f tured/weathered basement aquifers in tropical environments [60,73]. This concept developed by, inter alia, Wright [12], Chilton and Foster [13], Carter and Bennett [ Acworth [74], and Chilton and Smith-Carington [75].…”

“…These aquifers are defined by t association of an igneous or metamorphic fractured basement and a mantle of weather products resulting from the prolonged, progressive, in situ chemical degradation of basement rock into soil under tropical conditions. Detail of the typical vertical profil fractured/weathered basement aquifers in tropical environments, assembling the ab The Basement hosts aquifers that correspond to the classical concept of fractured/ weathered basement aquifers in tropical environments [60,73]. This concept was developed by, inter alia, Wright [12], Chilton and Foster [13], Carter and Bennett [67], Acworth [74], and Chilton and Smith-Carington [75].…”

Paleo-Geohydrology of Lake Chilwa, Malawi is the Source of Localised Groundwater Salinity and Rural Water Supply Challenges

“…Samples were collected in dedicated amber bottles for analysis of deuterium and oxygen-18 ratios at IAEA and CJF supported Malawi Government's Isotope Hydrology Laboratory (IHL). Analytical methods used have been recently reported by Banda et al [46,47].…”