Climate change and other disturbances significantly impact hydrogeochemical exports from mountainous headwater catchments such as the Upper Colorado River Basin. Developing a mechanistic understanding of how the physical and chemical processes interact in time and space in an integrated manner is key to quantifying the future impacts of such disturbances. The hydrogeochemical response of a mountainous catchment in the 2010–2019 period is evaluated quantitatively using a high-resolution model that simulates integrated hydrology, and transport and reactions for selected solutes and minerals. The model assumes that pyrite is present only at depth while calcite is distributed uniformly, and captures the observed C-Q reasonably well. Distinct C-Q dynamics are observed in an average (WY16), a wet (WY17), and a dry (WY18) water year. The model also quantifies the water fraction from surface, shallow and deep groundwater compartments using tracers, and suggests greater groundwater contributions to peak stream discharge in the dry WY18. Results demonstrate that calcium concentrations do not change significantly from year to year, while sulfate shows significant temporal variability. Pyrite dissolution is affected by the changing hydrological drivers where it is enhanced in the dry WY18; calcite dissolution supplements calcium dilution under high flow conditions. The model simulates the reaction hotspots controlled by hydrological conditions, and the spatially-resolved results show that higher soil saturation and less snowpack occur earlier on the south-facing side than on the north-facing side. This is a first-of-its-kind demonstration of a model that integrates hydrologic processes, including evapotranspiration, and reactive transport to enable a predictive understanding of hydrogeochemical exports.

中文翻译：

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使用综合地表-地下流动和反应输运模型了解山区流域的水文地球化学响应

气候变化和其他干扰严重影响山区源头流域（如上科罗拉多河流域）的水文地球化学出口。发展对物理和化学过程如何以综合方式在时间和空间中相互作用的机械理解是量化此类干扰的未来影响的关键。2010-2019 年山区集水区的水文地球化学响应使用高分辨率模型进行定量评估，该模型模拟选定溶质和矿物的综合水文、输运和反应。该模型假设黄铁矿仅存在于深度，而方解石均匀分布，并且相当好地捕获了观察到的 CQ。在平均 (WY16)、湿 (WY17) 和干 (WY18) 水年中观察到不同的 CQ 动态。该模型还使用示踪剂量化了地表、浅层和深层地下水隔间的水分数，并表明地下水对 2018 年旱季流量峰值的贡献更大。结果表明，钙浓度每年没有显着变化，而硫酸盐则表现出显着的时间变化。黄铁矿溶解受到不断变化的水文驱动因素的影响，在干燥的 WY18 中它会增强；方解石溶解在高流量条件下补充钙稀释。该模型模拟了受水文条件控制的反应热点，空间分辨结果表明，南侧土壤饱和度较高，积雪较少，发生时间早于北侧。