Riva M, Guadagnini L, Guadagnini A, Ptak T, Martac E
Dipartimento Ingegneria Idraulica, Ambientale, Infrastrutture Viarie, Rilevamento (D.I.I.A.R.) Politecnico di Milano, Piazza L. Da Vinci, 32, I-20133 Milano, Italy.
J Contam Hydrol. 2006 Nov 20;88(1-2):92-118. doi: 10.1016/j.jconhyd.2006.06.005. Epub 2006 Aug 10.
The delineation of well capture zones is of utmost environmental and engineering relevance as pumping wells are commonly used both for drinking water supply needs, where protection zones have to be defined, and for investigation and remediation of contaminated aquifers. We analyze the probabilistic nature of well capture zones within the well field located at the "Lauswiesen" experimental site. The test site is part of an alluvial heterogeneous aquifer located in the Neckar river valley, close to the city of Tübingen in South-West Germany. We explore the effect of different conceptual models of the structure of aquifer heterogeneities on the delineation of three-dimensional probabilistic well catchment and time-related capture zones, in the presence of migration of conservative solutes. The aquifer is modeled as a three-dimensional, doubly stochastic composite medium, where distributions of geo-materials and hydraulic properties are uncertain. We study the relative importance of uncertain facies geometry and uncertain hydraulic conductivity and porosity on predictions of catchment and solute time of travel to the pumping well by focusing on cases in which (1) the facies distribution is random, but the hydraulic properties of each material are fixed, and (2) both facies geometry and material properties vary stochastically. The problem is tackled within a conditional numerical Monte Carlo framework. Results are provided in terms of probabilistic demarcations of the three-dimensional well catchment and time-related capture zones. Our findings suggest that the uncertainty associated with the prediction of the location of the outer boundary of well catchment at the "Lauswiesen" site is significantly affected by the conceptual model adopted to incorporate the heterogeneous nature of the aquifer domain in a predictive framework. Taking into account randomness of both lithofacies distribution and materials hydraulic conductivity allows recognizing the existence of preferential flow paths that influence the extent of the well catchment and the solute travel time distribution at the site.
由于抽水井通常用于饮用水供应需求（此时必须定义保护区）以及污染含水层的调查与修复，因此确定井的捕获区具有极其重要的环境和工程意义。我们分析了位于“Lauswiesen”试验场的井场范围内井捕获区的概率性质。该试验场是位于德国西南部图宾根市附近内卡河谷的冲积非均质含水层的一部分。在存在保守溶质迁移的情况下，我们探讨了含水层非均质性结构的不同概念模型对三维概率性井集水区和与时间相关的捕获区划定的影响。该含水层被建模为三维双随机复合介质，其中地质材料和水力特性的分布是不确定的。我们通过关注以下两种情况来研究不确定的岩相几何形状以及不确定的水力传导率和孔隙率对集水区预测和溶质到达抽水井的时间的相对重要性：（1）岩相分布是随机的，但每种材料的水力特性是固定的；（2）岩相几何形状和材料特性均随机变化。该问题在条件数值蒙特卡罗框架内解决。结果以三维井集水区和与时间相关的捕获区的概率划定形式给出。我们的研究结果表明，在“Lauswiesen”场地，与井集水区外边界位置预测相关的不确定性受到在预测框架中纳入含水层区域非均质性质所采用的概念模型的显著影响。考虑到岩相分布和材料水力传导率的随机性，能够识别出影响该场地井集水区范围和溶质运移时间分布的优先流路径的存在。
