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

不能充分表征水导率(K)的空间分布是建立可靠的地下水流量和污染物运移预测模型、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，低钾相（如土壤层或湖相粘土）与高钾相（如沙和砾石冲洗液）并存是很常见的。在北美西部和中部平原的隐谷含水层中，渗透性冲蚀相组合形成了大型高产的区域性含水层系统。虽然高钾和低钾相的确切几何形状只能通过大量的地下信息来确定，但条件指示模拟提供了一种计算相分布的方法，这些相分布具有相同的空间协方差结构，并且符合现有数据。使用大量这些实现运行传输模拟，并检查模拟污染物移动时间的集中趋势和方差，或模拟污染物路径，可以深入了解污染物如何在真实系统中移动。然而，有条件指标模拟要求可以从现场数据中定义相组合空间协方差的适当指标变异函数模型，而实际上现场数据往往不足以达到这一目的。在本科院校研究计划下提出的研究目标是根据埋谷含水层系统中许多地点的实地数据确定变异函数模型。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。一名硕士学生将参与数据的地质统计学分析。将特定相组合的概念模型与变异函数模型相结合，形成定量的水相模型。当我们开始编目定量相模型时，我们将比较它们的相似性，并开始测试一个或多个原型定量水相的假设，可以为埋谷含水层系统中一般类型的相组合开发。

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.