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Evaluating recharge and dynamics of flow in the Lower Virgin River Basin, USA: Interpretation of hydrochemical and stable isotopic data.

机译：评估美国下维尔京河流域的补给量和水流动力学：水化学和稳定同位素数据的解释。

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摘要

Because of the complex geologic setting of the Basin and Range province, groundwater flow systems of the Intermountain basins of the southwestern United States are complex and remain poorly understood. Understanding these flow systems is important for water budgeting on a regional and local scale, and development of robust numerical groundwater models for sustainable water use and protection of water-dependent ecosystems. Although for decades hydrochemistry and isotopes have been used to characterize and trace subsurface water and surface water, effectively interpreting these data are still challenging, which can be attributed to existing subjective grouping of these data and the lack of methodological framework for analyzing and interpreting the data.;In this dissertation, new analytic approaches to analyze hydrochemical and stable isotopic data are described and used to trace the sources and movement of groundwater, and better quantify Virgin River interactions with groundwater in the lower Virgin River Basin in Nevada, Arizona, and Utah. In the new approach, data analytical techniques and data interpretations are combined in a sequential and mutually supportive way to test the hypotheses of potential interbasin groundwater flow, and Virgin River interaction with groundwater in the lower Virgin River Basin. To achieve these goals of the dissertation, three studies were conducted.;The objective of the first study was to optimize the multivariate statistical grouping of hydrochemical data of groundwater. The results indicated that repeated stable cluster solutions (robust hydrochemical facies) are obtained when cluster analysis is combined with Discriminant Function Analysis and agreement measures to group hydrochemical data. Also, this integrative approach allows for a quantification of the effect of analytical errors, outliers, and data transformation on the clustering of hydrochemical data. Using this approach, an optimal number of six robust hydrochemical facies were delineated for groundwater in the lower Virgin Valley. The results indicate that inappropriate data transformation can significantly impact the delineation of robust hydrochemical facies (Cramer's V < 0.8). In addition, the results indicate that analytical errors ≤= 19% and outliers ≤=7% can be ignored (Cramer's V > 0.8) in clustering.;The objective of the second study was to precisely define the sources of groundwater and Virgin River interactions with groundwater in the lower Virgin River Basin through a new approach for analyzing hydrochemical data of groundwater and surface water that allows for the precise definition of sources and discharge end-members, and overlay of interpretations. The methodology developed in the first objective above was used to delineate 6 robust hydrochemical facies for all waters in the basin. Subsequently, hydrochemical end-members were identified using the Schoeller diagram and discriminant functions plot. Flowpaths were tested, based on geographic coherence and patterns of the characteristic facies. Additionally, the PHREEQC inverse modeling code was used, beyond the contemporary application for identifying processes of hydrochemical evolution, to diagnose the significance of potential recharge sources to the lower Virgin River Basin. Mineral phases and constraints selected were based on compositional plots, saturation indices calculations, and the available geologic information. PHREEQC inverse modeling indicates that at least 80% of the groundwater in the lower Virgin River Basin is derived from interbasin flow. In addition, based on the hydrochemical data, the floodplain aquifer interacts highly with the Virgin River, but both are unlikely to be hydraulically connected to the underlying Muddy Creek Formation aquifer.;Finally in the third study, linear regression, Spearman correlation tests, scatterplot, box-and-whiskers plot, and Wilcoxon Rank Sum test are unconventionally applied to glean information from deltaD and delta18O, and Na, K, SO4, and Cl data of the hydrochemical facies delineated in Chapter 3. The deltaD values of the recharge end-members from adjacent basins and within the lower Virgin River Basin are high and significantly different from the low deltaD values of the discharge end members. Box-and-whiskers plot of delta18O values, comparing to box-and-whiskers plot of deltaD values, indicate possible oxygen isotopic exchange between the discharge groundwater and the aquifer minerals. The isotopic exchange implies a long residence time of the groundwater which discharges in the basin. Correlation tests of deltaD and delta18O versus Cl, and box-and-whiskers plots of deltaD, delta18O, and solute data indicate the Virgin River and floodplain aquifer are more homogeneous and evaporated than samples of the source/recharge and discharge end-members. Regionally transported deep carbonate water is invoked as possible explanation of the low deltaD values of the discharge waters in the lower Virgin River Basin. Mixing calculations for stable isotopes indicate that at least 50% of the groundwater discharging in the lower Virgin River Basin derives from interbasin groundwater sources. Although this estimate is different from the estimates presented in Chapter 3, both results reinforce the significance of interbasin groundwater to the lower River Virgin Basin.
机译：由于盆地和山脉省的地质环境复杂，美国西南部山间盆地的地下水流系统非常复杂，人们对其了解仍然很少。了解这些流量系统对于区域和地方范围内的水预算以及开发用于可持续用水和保护依赖水的生态系统的可靠的地下水数值模型至关重要。尽管几十年来一直使用水化学和同位素来表征和追踪地下水和地表水，但是有效地解释这些数据仍然具有挑战性，这可以归因于这些数据的现有主观分组以及缺乏用于分析和解释数据的方法框架在本文中，描述了用于分析水化学和稳定同位素数据的新分析方法，并将其用于追踪地下水的来源和运动，并更好地量化内华达州，亚利桑那州和犹他州下维京河流域中维京河与地下水的相互作用。在新方法中，数据分析技术和数据解释以相继和相互支持的方式相结合，以检验潜在的盆地间地下水流动以及维京河与维珍河下游地区地下水之间相互作用的假设。为实现本文的这些目的，进行了三项研究。；第一项研究的目的是优化地下水水化学数据的多元统计分组。结果表明，将聚类分析与判别函数分析和一致性措施组合以对水化学数据进行分组时，可以获得重复稳定的聚类解决方案（鲁棒的水化学相）。同样，这种综合方法可以量化分析误差，离群值和数据转换对水化学数据聚类的影响。使用这种方法，在维京河下游地区确定了六个最佳的鲁棒水化学相。结果表明，不适当的数据转换会严重影响稳固水化学相的描述（Cramer V <0.8）。此外，结果表明在聚类中可以忽略分析误差≤= 19％和离群值≤= 7％（Cramer V> 0.8）.;第二项研究的目的是精确定义地下水与维京河相互作用的来源通过一种分析地下水和地表水的水化学数据的新方法来分析维珍河下游地区的地下水，从而可以精确定义水源和排放端成员，并覆盖各种解释。在上述第一个目标中开发的方法用于描述该盆地所有水域的6个鲁棒的水化学相。随后，使用Schoeller图和判别函数图确定水化学末端成员。根据地理连贯性和特征相的模式对流动路径进行了测试。此外，除了现代应用程序以外，还使用PHREEQC逆建模代码来识别水化学演化过程，以诊断潜在的维珍河流域补给源的重要性。选择的矿物相和约束条件基于成分图，饱和度指数计算和可用的地质信息。 PHREEQC反演模型表明，维珍河下游流域至少有80％的地下水来自盆地间流。此外，根据水化学数据，洪泛区含水层与维京河之间的相互作用极强，但两者均不可能与下伏的Muddy Creek地层含水层保持水力联系。最后，在第三项研究中，采用线性回归，Spearman相关检验，散点图，箱须图和Wilcoxon秩和检验非常规地应用于deltaD和delta18O以及第3章中描述的水化相的Na，K，SO4和Cl数据的收集信息。补给端的delDD值-相邻流域和维珍河下游地区的流域成员数量较高，并且与排放端成员的低delDD值显着不同。与deltaD值的方差图相比，delta18O值的方差图表明，排出的地下水和含水层矿物之间可能存在氧同位素交换。同位素交换意味着在盆地中排放的地下水的停留时间较长。 deltaD和delta18O与Cl的相关性测试以及deltaD，delta18O的箱形图和溶质数据表明，维珍河和洪泛区含水层比源端/补给端和排放端成员的样本更均匀和蒸发。调用区域输送的深层碳酸盐水可能解释了维珍河下游地区排放水的低ΔD值。稳定同位素的混合计算表明，维珍河下游地区至少50％的地下水排放源于盆地间的地下水源。尽管该估算值与第3章中给出的估算值不同，但这两个结果都增强了盆地间地下水对维京河下游地区的重要性。

著录项

  • 作者

    Asante, Joseph.;

  • 作者单位

    University of Nevada, Las Vegas.;

  • 授予单位 University of Nevada, Las Vegas.;
  • 学科 Hydrology.;Geology.;Environmental Sciences.
  • 学位 Ph.D.
  • 年度 2012
  • 页码 156 p.
  • 总页数 156
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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