Enhancing Water Security through Water Harvesting and Groundwater Recharge in Arid and Semi-Arid Regions: A Case Study from Yechilla area, Tigray (Northern Ethiopia)

Abstract

Water scarcity in arid and semi-arid regions, aggravated by climate change and population growth, poses significant challenges to sustainable development, particularly in Sub-Saharan Africa. Groundwater depletion, driven by overexploitation and reduced recharge, threatens water security, food production, and ecosystem stability. Water harvesting (WH) and groundwater recharge (GWR) strategies offer viable solutions to enhance water availability and resilience. This study focuses on the geological, hydrogeological, and engineering geological characterization of Yechilla, Central Tigray, Northern Ethiopia, to assess its suitability for WH and artificial recharge (AR) aimed at improving water security and sustainability. The study area is situated within the Tekeze River Basin (TRB) and encompasses seven lithologic units: metavolcanic, metasediments, granite intrusions, sandstone, trap basalt, dolerite sills, and alluvial deposits. Detailed field data collection including soil sampling and description, infiltration test, discontinuity measurements and UCS (Schmidt hammer test) were done during the extended research study. Laboratory soil textural analysis, employing sieve and hydrometer methods, was used to classify soils based on hydrologic soil groups (HSG). A GIS-based multi-criteria decision-making method was employed to identify potential WH and GWR zones, utilizing eight criteria: lithology, soil texture, slope, elevation, drainage density, lineament density, rainfall, and land use/land cover (LULC). The relative importance of each factor was determined through pairwise comparisons using the Analytical Hierarchy Process (AHP). Suitability classes were assigned to all parameters, followed by weighted overlay analysis in ArcGIS 10.8 to generate integrated suitability maps, which were validated using field data and high-resolution Google Earth imagery with ROC-AUC curve analysis. Results indicate that fluvial soils, composed of over 97% sand, exhibit high infiltration rates and low runoff potential, whereas residual soils formed from in-situ weathering display varied textures—including clay, sand, and loam—that influence water retention and runoff properties. Infiltration tests revealed rates ranging from 0.2 cm/hour (slow) in clay soils to 4.7 cm/hour (medium) in sandy soils. The final suitability map classified WH zones as 14.20% (very high), 29.50% (high), 22.00% (moderate), 22.40% (low), and 11.90% (unsuitable), while GWR yielded 11.30%, 24.34%, 33.90%, 26.85%, and 3.64%, respectively. With AUC values of 80.10% (WH) and 84.30% (GWR), the study demonstrates that the AHP method, combined with field validation, effectively identifies appropriate potential zones. These findings offer decision-makers and planners a robust framework for developing effective water management strategies by pinpointing optimal sites for water harvesting and groundwater recharge, thereby promoting sustainable water sources in Yechilla and similar water-scarce regions.