RUI: Predicting Transport Through Heterogeneous Facies Assemblages: Geostatistical Anatomy of Buried-Valley Aquifers

无法充分表征水力传导率（K）的空间分布，是构建地下水流和污染物迁移的可靠预测模型、修复地下水污染以及有效管理和保护地下水资源的障碍。 在冰川衍生的含水层中，通常同​​时存在低 K 相（例如耕土或湖相粘土）和高 K 相（例如砂砾石冲刷）。 在北美西部和中部平原的潜谷含水层中，渗透性冲刷相组合形成了大型且多产的区域含水层系统。 尽管高 K 相和低 K 相的精确几何形状只能通过大量的地下信息来确定，但条件指示符模拟提供了一种方法来计算具有相同空间协方差结构并尊重可用数据的相分布的许多实现。 使用大量这些实现来运行运输模拟，并检查模拟污染物传播时间或模拟污染物路径的集中趋势和方差，可以深入了解污染物如何在真实系统中移动。 然而，条件指示符模拟要求可以根据现场数据定义相组合空间协方差的适当指示符变差函数模型，而实际上现场数据通常不足以实现此目的。 本科院校研究计划下拟议研究的目标是根据潜谷含水层系统中多个地点的现场数据确定变差函数模型。 两名本科生将参与实地工作，为他们的高级研究项目奠定基础。 一名硕士学位学生将参与数据的地统计分析。 特定相组合的概念模型将与变差函数模型相结合，以创建定量水相模型。 当我们开始对定量相模型进行编目时，我们将比较它们的相似性，并开始检验这样的假设：可以为潜谷含水层系统中的一般类型相组合开发一种或多种原型定量水相。

The inability to sufficiently characterize the spatial distribution of hydraulic conductivity (K) is an obstacle to constructing reliable predictive models of ground-water flow and pollutant transport, to remediating ground-water contamination, and to effectively managing and protecting ground-water resources. In glacially derived aquifers, it is common to have low-K facies (e.g. till or lacustrine clay) juxtaposed with high-K facies (e.g. sand and gravel outwash). In the buried-valley aquifers of the western and central plains of North America, assemblages of permeable outwash facies form large and productive regional aquifer systems. Although the exact geometry of the high-K and low-K facies can only be determined by a prohibitive amount of subsurface information, conditional indicator simulation provides a way to compute a number of realizations of facies distributions that have identical spatial covariance structure and that honor available data. Running transport simulations using a large number of these realizations, and examining the central tendency and variance of simulated contaminant travel times, or the simulated contaminant pathways, can give insight into how contaminants will move through the real system. However, conditional indicator simulations require that an adequate indicator variogram model of the spatial covariance of the facies assemblage can be defined from field data, when in fact the field data are often insufficient for this purpose. The objective of the proposed research under the Research at Undergraduate Institutions Program is to determine variogram models from field data at a number of locations in a buried-valley aquifer system. Two undergraduate students will be involved in field work that will create the basis for their senior research projects. One M.S. student will be involved in the geostatistical analysis of the data. The conceptual model of a specific facies assemblage will be combined with the variogram model to crate a quantitative hydrofacies model. As we begin to catalogue quantitative facies models, we will compare them for similarities and begin to test the hypothesis that one or more archetypal quantitative hydrofacies can be developed for general types of facies assemblages in buried-valley aquifer systems.