Application of geostatistical methods and well-Specific Capacity for aquifer characterization in the volcanic terrain, upper Awash River sub-basin, Ethiopia

Abstract Groundwater is the primary source of water in Ethiopia’s upper Awash River Sub-Basin, where surface water availability is unreliable. Estimating aquifer parameters such as transmissivity (T) and hydraulic conductivity (K) is crucial for characterizing groundwater systems, but are often constrained by the cost and logistical challenges of pumping tests, particularly in fractured volcanic terrains. This study demonstrates the use of well-specific capacity (Sc) as a cost-effective proxy for T and K estimation, combined with geostatistical interpolation. A dataset of 341 wells was analyzed and grouped into seven hydrogeological zones. A strong empirical relationship was derived (T = 1.528·Sc1.082, R² = 0.94), with bootstrapping and cross-validation confirming its predictive capacity and uncertainty bounds. The spatial variability of T and K was mapped using ordinary kriging, which outperformed inverse distance weighting. The results showed higher T and K values in fractured volcanic units and lower values in massive formations, reflecting the structural and lithological control of groundwater flow. This integrated approach reduces reliance on expensive tests and provides a practical framework for evaluating aquifercharacterization in data-scarce volcanic regions, thereby supporting improved groundwater management and sustainable abstraction strategies.