Characterization of Major Alluvial Aquifers of Ethiopia and Determination of their Vulnerability to Climate and Land cover Changes
No Thumbnail Available
Date
2024-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
Water is an essential resource for the sustainability of life. Goals for access to clean water, the growth of the energy sector, and food security can all be met with the help of climate-resilient groundwater management. Nonetheless, not much study has been done to evaluate Ethiopia's groundwater resources. The purpose of this study was to examine the physical attributes of Ethiopia's principal alluvial aquifers and determine how sensitive they were to changes in the country's climate and land cover. Geographic information systems (GIS), remote sensing, the analytic hierarchy process (AHP) method of multicriteria decision-making (MCDM), and machine learning algorithms (MLAs) were all utilized in the first segment. The hydro-geological, climatic, and land use land cover (LULC) characteristics were explored as potential influencing variables for groundwater in the study regions. Following that, the stable isotope and geochemical analysis were employed to better understand the groundwater and the underlying geological components. Examination of aquifer vulnerability using a modified DRASTIC index was the third technique implemented. The study's other main emphasis was the effect of changing climate and land cover on groundwater. Independent research on LULC and climate change was also conducted in this part. Lastly, the study looked at how groundwater is affected by changes in climate and land cover together. According to the groundwater potential analysis, 81.93% of Fafen-Jerer, 22.35% of Gambela, and 17.38% of Shinile are classified as low and very low potential zones. The high and very high groundwater potential zone covers 4.32% of Fafen-Jerer, 55.52% of Gambela, and 64.8% of the Shinile sub-basin. The key criteria highly influencing groundwater potential in the research areas are geomorphology, rainfall, and geology. The geochemical analysis indicates that the predominant cation and anion concentrations are Ca2+ > Na+ > Mg2+ > K+ and SO4 2- > HCO3 - > Cl-> NO3 - respectively. The groundwater in the study sites is slightly alkaline and quite hard. Mixed (Na-Mg-Ca) water is the most prevalent water type kind in the research area. The primary hydrochemical process is the interaction between rocks and water. The isotope analysis revealed that groundwater samples of hydrogen and oxygen isotopic compositions were mostly concentrated close to the meteoric water line. The results demonstrate that precipitation has been found to have more enriched isotope compositions than groundwater at both locations (Dire Dawa and Jigjiga). The LULC's findings show that croplands have reduced, whereas forests have increased significantly in coverage in the western catchment (WC). The LULC shift for the eastern catchment (EC) indicates an increase in area coverage of grasslands, croplands, and urban areas, XVIII and a reduction in shrublands, and barren. Climate research reveals that climate change will be a major concern for water supplies in the studied regions. Over the reference period (1981-2010), the WC and EC had annual temperature rises of 1.5 and 0.06 oC, and annual precipitation declines of 15.73 and 3.68 mm/year respectively. These changes in these core climatic parameters continue to affect future cases. According to the UNEP aridity index (AI) and De Martone aridity index (DMI) results the aridity indices also followed a downward trend for the past periods. These changes shift the climate characters from humidity conditions to semi-arid and arid climates. According to the study, the effect of climatic change is more pronounced in the WC than in the EC. The results of the current period's climate change show that it is particularly robust in the study regions' dry corners. The effect of climate on groundwater will be pronounced in these regions by the end of 2070. The outputs of this research should provide a significant understanding of Ethiopian alluvial aquifer zones for future studies in paleoclimatology, hydrogeology, meteorology, and geomorphology. The study's findings might be useful for water resource and environmental management, as well as policy and decision-making.
Description
Keywords
Alluvial aquifers, Aridity Indices, GCM, Geospatial, Groundwater potential, IsotopeGeochemistry, MODIS