Regional groundwater flow in structurally-complex extended terranes: An evaluation of the sources of discharge at Ash Meadows, Nevada
Regional groundwater flow in structurally-complex extended terranes: An evaluation of the sources of discharge at Ash Meadows, Nevada
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结构复杂的扩展地体中的区域地下水流：内华达州 Ash Meadows 排放源评估
DOI：
10.1016/j.jhydrol.2010.03.013
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发表时间：
2010
影响因子：
6.4
通讯作者：
D. Eggett
中科院分区：
文献类型：
--
作者：
M. Bushman;S. Nelson;D. Tingey;D. Eggett
美国内华达州阿什梅多斯 (Ash Meadows) 是干旱莫哈韦沙漠中地下水主要排放地（约 38,000 升/分钟），栖息着许多特有和受威胁的湿地物种。除了这些资源之外，阿什梅多斯还可能代表内华达试验场核武器试验中充满放射性核素的水的未来排放地点。然而，更重要的是，Ash Meadows 提供了了解通过裂隙基岩对盆地之间水输送的控制的机会。将文献中的 4000 多种溶质分析汇总到一个数据库中。对数据的空间分布、完整性、电荷平衡和升高温度（⩾20°C 和区域水流系统内）进行了筛选，除了 Ash Meadows 本身之外，还有 246 个候选上梯度水分布在六个潜在源区中。这些潜在来源包括碳酸盐、火山和可能的山谷含水层系统。通过聚类分析对这些水域进行了表征，以便以客观的方式将相似的水域分类为潜在的流动路径，并为反演地球化学模型和其他分析模式建立代表性的端元水域。同位素示踪剂，无论是保守的还是反映水-岩相互作用的，都表明灰草甸的水是由火山地体向南流动而产生的，与活跃的区域东西向延伸引起的首选渗透结构平行。溶质平衡支持这一结论。然而，这与普遍的模型背道而驰，即阿什梅多斯的水是从斯普林山脉和帕拉纳加特山谷地区通过流域间水流流经连续的裂隙碳酸盐含水层而产生的东向和东北向水流。这项工作表明，扩展地体中的碳酸盐含水层系统比以前认识的更加划分，并且裂缝渗透率的各向异性是划分和控制流动方向的关键。
Ash Meadows, Nevada, USA is a site of major groundwater discharge (∼38,000 L/min) in the arid Mojave Desert, and hosts a number of endemic and threatened wetland species. In addition to these resources, Ash Meadows may also represent the future discharge location of radionuclide-laden waters from nuclear weapons testing at the Nevada Test Site. More importantly, however, Ash Meadows provides the opportunity to understand the controls on water transfer between basins through fractured bedrock. 4000+ solute analyses were assembled from the literature into a single database. The data were screened for spatial distribution, completeness, charge balance, and elevated temperatures (⩾20°C and within regional flow systems), with 246 candidate up-gradient water remaining distributed among six potential source areas in addition to and Ash Meadows itself. These potential sources include both carbonate, volcanic and perhaps valley-fill aquifer systems. These waters were characterized by cluster analysis in order to sort similar waters in an objective fashion into potential flow paths and to establish representative endmember waters for inverse geochemical models and other modes of analysis. Isotopic tracers, both conservative and those reflecting water–rock interaction, all suggest that waters at Ash Meadows are derived by southward flow from volcanic terranes, parallel to the preferred permeability structure induced by active regional east–west extension. Solute balances support this conclusion. However, this runs counter to the prevailing model that waters at Ash Meadows are derived from easterly and northeasterly flows from the Spring Mountains and Pahranagat Valley areas by interbasin flow through a continuous fractured carbonate aquifer. This work suggests that carbonate aquifer systems in extended terranes are more compartmentalized than previously appreciated and that anisotropy in fracture permeability is key to compartmentalization and the control of flow directions.