Hydro-geochemical investigation and Water Quality Mapping in the Upper Beshilo Watershed, Southern Wollo, Ethiopia

The Upper Beshilo watershed within the Upper Blue Nile Basin (UBNB) is a region experiencing escalating groundwater reliance for domestic and agricultural purposes. Yet, it lacks comprehensive hydrogeochemical and isotopic characterization. This study addresses this critical knowledge gap by investigating the hydrogeochemical characteristics and isotopic signatures of groundwater from various sources (springs, boreholes, hand-dug wells, rivers, and marsh areas) across the watershed. The objective is to elucidate groundwater flow patterns, recharge and discharge dynamics, sources of contamination (including waste from Mekdela Amba University and Ginba town), and the overall hydrogeological evolution of the system. Twenty-six water samples were collected and analyzed for major ions and stable isotopes (δ²H and δ¹⁸O). Results indicate that precipitation is the primary recharge source, with the dominant water types identified as Ca-Na-HCO₃ and Ca-HCO₃, suggestive of fresh recharge and early to intermediate stages of groundwater evolution. However, the hydrochemical data also reveals the impact of anthropogenic activities, with elevated levels of nitrate, sulfate, and chloride near discharge zones and downstream areas, particularly around Ginba town and the Mekdela Amba University waste site. Isotopic analysis confirms that the groundwater system is recharged by precipitation, with deeper boreholes showing more depleted isotope signatures indicative of past climate conditions, while shallow groundwater sources show evidence of more recent recharge. Additionally, evaporation processes were observed in surface water. A conceptual hydrogeological model was constructed depicting recharge areas in the south and southwestern highlands and discharge zones towards the lowlands and the Beshilo River, following a general northward flow pattern. This comprehensive study provides crucial insights into the hydrogeological system of the Upper Beshilo watershed, underscoring the need for sustainable groundwater management practices. These include the importance of protecting recharge zones, implementing proper waste management strategies, and emphasizing ongoing monitoring to prevent future degradation of this valuable resource, while also guiding the development of the resource in terms of drinking water provision, bottled water production, and location of boreholes. Keywords: Anthropogenic impact; Water quality; Upper Beshilo watershed; Upper Blue Nile Basin