Integrated analysis of surface water-groundwater interactions and enhanced hydrological forecasting of glacierized river in cold and arid regions

In cold and arid regions, climate change has altered precipitation patterns and accelerated glacierized retreat, which imposes severe risks on the stability of regional hydrological systems. Combined with the strong interactions between surface water (SW) and groundwater (GW) regulated by distinctive geological conditions, clarifying the baseline hydrological regime and predicting future hydrological changes is critical to maintaining local ecosystem stability. The headwater catchment of the Bortala River in Northwest China represents a typical glacierized watershed dominated by spring-fed discharge. Under the continuous influence of climate change, quantitative investigations into surface water-groundwater interactions in this catchment are still inadequate. In this study, a coupled SWAT-MODFLOW model embedded with a glacier module was developed to clarify the surface water-groundwater interactions relationship. Based on the Budyko framework, under CMIP6 climate scenarios, to establish an optimized decomposition and reconstruction simulation system, furthermore, to explore the changing characteristics of temperature, precipitation, and runoff. Observed hydrometeorological parameters were utilized to calibrate and validate the established model. A set of statistical indices was employed to assess the modeling performance, and the coupled model attained favorable simulation accuracy. The main results indicated that although surface water served as the dominant recharge source for groundwater from 1971 to 2020, representing a cumulative reduction of 26.7% from the initial value of the historical period, and an increased average annual decline rate of 0.45%. Future scenario projections revealed an increasing trend in total watershed runoff under both SSP2-4.5 and SSP5-8.5, with growth rates of 13.6% and 14.2%, respectively. A runoff inflection point is projected to occur around the 2070s (± 10 years), which will appear approximately 10 years earlier under the high-emission SSP5-8.5 scenario. In addition, intensified precipitation extremes may trigger severe hydrological risks, which are expected to concentrate around the 2040s and 2070s.