The objective of this study was to comprehensively evaluate and interpret hydrogeochemically the extensive legacy surface-water data for the expansive Republican River watershed in southcentral Nebraska. Historical (1968–1991) hydrochemistry data [major cations and anions, total salinity [specific conductance (SC)] and pH supplied by the Nebraska Department of Environmental Quality and the US Geological Survey were hydrogeochemically and statistically analyzed. Interpretation of this large legacy dataset (315 sample analyses at 12 Republican River sampling stations) revealed that the Republican River’s range in SC is relatively low (200–1020 µS/cm), with a river-wide median of 587 µS/cm (~ 380 mg/L). The range in SC for 10 tributaries (204 sample analyses) is 190–2910 µS/cm with a median value of 550 µS/cm (~ 360 mg/L). The Ca–HCO₃ hydrochemical facies dominates throughout the watershed followed by the Na–HCO₃ facies. Hydrochemical equilibrium modeling reveals that most samples occurred in an aqueous environment characterized by gypsum undersaturation but slight calcite and dolomite supersaturation; low supersaturation values comprise a line of evidence for the thermodynamic equilibrium or near equilibrium of the studied surface waters. Scatter plots of meq/L concentrations for selected anions and cations reveal the impact of silicate mineral (e.g., feldspars) weathering on the aqueous hydrochemistry throughout the watershed. These ubiquitous feldspar minerals most likely originated along the eastern slope of the Front Range during Late Cretaceous time (Laramide Orogeny) and were subsequently transported into the study area. The relatively high concentrations of sulfate and sodium in numerous samples collected from the Arikaree River probably originate in the underlying Pierre Shale, rich in S-bearing minerals.

这项研究的目的是对内布拉斯加州中南部广阔的共和河流域的广泛的遗留地表水数据进行水文地球化学综合评价和解释。内布拉斯加州环境质量部和美国地质调查局提供的历史（1968-1991年）水化学数据[主要阳离子和阴离子，总盐度[比电导（SC）]和pH值已通过水地球化学和统计学方法得到了分析。对该大型遗留数据集的解释（在12个共和党河采样站进行了315个样本分析）表明，共和党河在南卡罗来纳州的范围相对较低（200–1020 µS / cm），河水的中位数为587 µS / cm（〜 380 mg / L）。10个支流的SC范围（204个样品分析）为190–2910 µS / cm，中位值为550 µS / cm（〜360 mg / L）。Ca–HCO流域内_3个水化学相占主导地位，其次是Na–HCO ₃相。水化学平衡模型表明，大多数样品都发生在以石膏欠饱和为特征但方解石和白云石略有过饱和的水性环境中。低的过饱和度值表明了所研究地表水的热力学平衡或接近平衡。所选阴离子和阳离子的meq / L浓度散点图揭示了硅酸盐矿物（例如长石）风化对整个流域中水化学的影响。这些无处不在的长石矿物最有可能起源于白垩纪晚期（前拉美尔造山带）沿锋山脉的东坡，随后被运入研究区。