Institute of Environmental Management and Quality Control

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    Decadal Spatiotemporal Trends in Stable Isotopes and Hydrochemistry of Surface Water and Groundwater in Guanzhong Basin, China
    (Wiley, 2026-08-27) Kallon, Hadji Dauda Smaila
    In arid regions, water scarcity poses a critical challenge to sustainable development, underscoring the need to comprehensively assess hydrological processes, hydrochemical dynamics, and their drivers under changing climatic conditions. This study aims to reveal the decadal spatiotemporal evolution of water isotopes and hydrochemical characteristics in the Guanzhong Basin, quantify long‐term variations in surface water–groundwater recharge patterns under climate change and anthropogenic water regulation, and clarify the natural and anthropogenic mechanisms governing water geochemical evolution. Results show consistent hydrochemical patterns across both surface water and groundwater, with dominant cations in the order Na + > Ca 2+ > Mg 2+ > K + and dominant anions in the order HCO 3 − > SO 4 2− > Cl − . The prevalence of HCO 3 − , SO 4 2− , Na + , and Ca 2+ reflects combined controls of rock weathering and evaporation–crystallization processes, with Gibbs diagrams confirming mineral weathering as the primary mechanism governing water chemistry. Groundwater samples were predominantly of the HCO 3 –Ca Mg type, whereas surface water showed more diverse hydrochemical facies, including SO 4 Cl–Ca Mg and HCO 3 –Na types. A shift from Cl − dominance in 2014 to HCO 3 − dominance in 2024 indicates enhanced weathering processes. Stable isotope analyses (δ 18 O, δ 2 H) reveal a transition from arid conditions toward increased humidity in 2024, whereas rising d‐excess values suggest expanded recharge sources and recycled moisture contributions. Isotopic evidence indicates a marked reversal in recharge dynamics: Surface water predominantly recharged groundwater in 2014 (56.76%), whereas groundwater became the dominant contributor to surface water in 2024 (90.87%), particularly in the midstream basin. Although carbonate and silicate weathering remain the principal hydrochemical controls, increasing anthropogenic activities and climatic pressures are reshaping groundwater geochemistry. These findings highlight the necessity of integrated water resource management and provide valuable insights for semiarid basins facing similar hydrological transitions.
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    Estimating Baseflow Dynamics and Influencing Factors Using WHAT in the Wei River Basin, China
    (Wiley, 2026-09-01) Kallon, Hadji Dauda Smaila
    Baseflow is critical for sustaining streamflow and managing groundwater resources. The Wei River Basin (WRB) is a semi‐humid region with high water demand that requires robust baseflow analysis, which is essential for stream restoration. Annual baseflow in the WRB was estimated using the Web‐based Hydrograph Analysis Tool (WHAT) in this study, which utilised streamflow data from five gauged watershed stations. Groundwater‐level monitoring data from 2010 to 2015 were also utilised to understand the interaction between baseflow and groundwater levels. The two‐parameter recursive digital filter method within the WHAT programme was employed to estimate baseflow from daily streamflow records. By leveraging this standardised, peer‐validated tool, our analysis maintained consistency in baseflow and direct runoff calculations across all monitoring stations, reducing subjectivity in manual separation methods and enhancing comparability of results. Based on the results, the total annual baseflow measured between 2010 and 2019 ranged from 29574.74 to 910078.73 m 3 /s, while the baseflow index (BFI) varied from 0.56 to 0.67. During the study period, the average BFI was calculated to be 0.63, indicating that baseflow contributed approximately 64% of the long‐term runoff in the examined watersheds. The results also revealed a progressive rise in the BFI along the Wei River, increasing from 0.56 in the upstream sections to 0.67 downstream. Baseflow and BFI spatial patterns indicate groundwater abundance, driven by climate and human factors, with climate more influencing baseflow variability from west to east. Between 2010 and 2019, the basin experienced significant LULC changes. These changes serve as a critical contributing factor modulating decadal baseflow variation, while climate variability remains a dominant driver. Cropland declined, forest and water‐type areas increased, grassland and unused land decreased, and the impervious area expanded. These LULC changes led to a significant increase in annual baseflow despite the climate zone remaining the same.