Characterizing shallow groundwater in hillslope aquifers using isotopic signatures: A case study in the Upper Blue Nile basin, Ethiopia

Robit-Bata watershed, Upper Blue Nile basin, Ethiopia. Stable isotopes of water (Oxygen-18 and Deuterium) were used as tracers to estimate the contribution groundwater in shallow hillslope aquifers streamflow watershed. To assess spatiotemporal variability develop a hydrograph separation technique, we collected rainfall, groundwater, samples analyzed their δ18O δ2H isotopic compositions. The local meteoric line (LMWL) evaporative (LEL) study area determined compared with global (GMWL). A standard unweighted two-component isotope-based model was determine percentage streamflow. LMWL (δ2H = 8.63·δ18O + 18.2) mostly showed heavy enrichment relative GMWL, LEL 5.45·δ18O 6.96) indicated Ethiopian lakes. Shallow responded rapidly good spatial correlation depending on topographic positions wells. Pre-event contributed <50% peak discharge July, but >90% when watershed reached maximum storage. This finding gives insight towards predominant runoff generation process has significant implications for sustainable dry season irrigation expansion sub-surface flow drains out from October onwards reducing tables