Sasidharan Salini, Bradford Scott A, Šimůnek Jiří, Kraemer Stephen R
Department of Environmental Sciences, University of California Riverside, Riverside, CA 92521, USA.
United States Department of Agriculture, Agricultural Research Service, U. S. Salinity Laboratory, Riverside, CA 92507, USA.
J Hydrol (Amst). 2019 Mar;570:598-611. doi: 10.1016/j.jhydrol.2018.12.073.
Drywells are increasingly used to capture stormwater runoff for surface infiltration and aquifer recharge, but little research has examined the role of ubiquitous subsurface heterogeneity in hydraulic properties on drywell performance. Numerical experiments were therefore conducted using the HYDRUS (2D/3D) software to systematically study the influence of subsurface heterogeneity on drywell infiltration. Subsurface heterogeneity was described deterministically by defining soil layers or lenses, or by generating stochastic realizations of soil hydraulic properties with selected variance () and horizontal () and vertical () correlation lengths. The infiltration rate increased when a high permeability layer/lens was located at the bottom of the drywell, and had larger vertical and especially horizontal dimensions. Furthermore, the average cumulative infiltration () for 100 stochastic realizations of a given subsurface heterogeneity increased with and , but decreased with . This indicates that the presence of many highly permeable, laterally extending lenses provides a larger surface area for enhanced infiltration than the presence of isolated, highly permeable lenses. The ability to inversely determine soil hydraulic properties from numerical drywell infiltration results was also investigated. The hydraulic properties and the lateral extension of a highly permeable lens could be accurately determined for certain idealized situations (e.g., simple layered profiles) using constant head tests. However, variability in soil hydraulic properties could not be accurately determined for systems that exhibited more realistic stochastic heterogeneity. In this case, the heterogeneous profile could be replaced with an equivalent homogeneous profile and values of an effective isotropic saturated conductivity (Ks) and the shape parameter in the soil water retention function (α) could be inversely determined. The average value of Ks for 100 stochastic realizations showed a similar dependency to on , , and Whereas, the average value of α had large confidence interval for soil heterogeneity parameters and played a secondary role in drywell infiltration. This research provides valuable insight on the selection of site, design, installation, and long-term performance of a drywell.
渗水井越来越多地用于收集雨水径流，以进行地表渗透和含水层补给，但很少有研究探讨普遍存在的地下水力特性非均质性对渗水井性能的影响。因此，利用HYDRUS（2D/3D）软件进行了数值试验，以系统地研究地下非均质性对渗水井入渗的影响。地下非均质性通过定义土层或透镜体来确定性地描述，或者通过生成具有选定方差（）以及水平（）和垂直（）相关长度的土壤水力特性的随机实现来描述。当高渗透层/透镜体位于渗水井底部且具有较大的垂直尺寸，尤其是水平尺寸时，入渗率会增加。此外，对于给定地下非均质性的100次随机实现，平均累积入渗量（）随 和 增加，但随 减小。这表明，许多横向延伸的高渗透透镜体的存在比孤立的高渗透透镜体的存在提供了更大的表面积以增强入渗。还研究了根据数值渗水井入渗结果反演确定土壤水力特性的能力。对于某些理想化情况（例如简单分层剖面），使用常水头试验可以准确确定高渗透透镜体的水力特性和横向延伸。然而，对于表现出更现实的随机非均质性的系统，无法准确确定土壤水力特性的变异性。在这种情况下，可以用等效的均质剖面代替非均质剖面，并反演确定有效各向同性饱和导水率（Ks）和土壤水分保持函数（α）中的形状参数的值。100次随机实现的Ks平均值对 、 和 的依赖性与 相似。而对于土壤非均质性参数，α的平均值具有较大的置信区间，并且在渗水井入渗中起次要作用。这项研究为渗水井的选址、设计、安装和长期性能提供了有价值的见解。
