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 (σ) and horizontal (X) and vertical (Z) 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 (I) for 100 stochastic realizations of a given subsurface heterogeneity increased with σ and X, but decreased with Z. 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 I on σ, X, and Z. 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.

中文翻译：

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非均质土壤剖面中的干井入渗和水力特性

干井越来越多地用于捕获雨水径流以进行地表渗透和含水层补给，但很少有研究检查无处不在的地下异质性对干井性能的水力特性的作用。因此，使用 HYDRUS (2D/3D) 软件进行了数值实验，以系统地研究地下异质性对干井渗透的影响。通过定义土壤层或透镜，或通过生成具有选定方差 (σ) 和水平 (X) 和垂直 (Z) 相关长度的土壤水力特性的随机实现，确定性地描述了地下异质性。当高渗透层/透镜位于干井底部并且具有更大的垂直特别是水平尺寸时，渗透率增加。此外，给定地下异质性的 100 次随机实现的平均累积渗透 (I) 随 σ 和 X 增加，但随 Z 减少。这表明许多高渗透性、横向延伸的透镜的存在为增强渗透提供了更大的表面积存在孤立的、高渗透性的镜片。还研究了从数值干井入渗结果反向确定土壤水力特性的能力。对于某些理想化的情况（例如，简单的分层轮廓），可以使用恒定水头测试准确地确定高渗透性镜片的液压特性和横向延伸。然而，对于表现出更现实的随机异质性的系统，无法准确确定土壤水力特性的可变性。在这种情况下，异质剖面可以用等效的均质剖面代替，有效各向同性饱和电导率 (Ks) 的值和土壤保水函数 (α) 中的形状参数可以反向确定。100 次随机实现的 Ks 平均值显示出与 I 对 σ、X 和 Z 的相似依赖性。而 α 的平均值对于土壤非均质性参数具有较大的置信区间，并且在干井入渗中起次要作用。这项研究为干井的选址、设计、安装和长期性能提供了宝贵的见解。100 次随机实现的 Ks 平均值显示出与 I 对 σ、X 和 Z 类似的依赖性。而 α 的平均值对于土壤非均质性参数具有较大的置信区间，并且在干井入渗中起次要作用。这项研究为干井的选址、设计、安装和长期性能提供了宝贵的见解。100 次随机实现的 Ks 平均值显示出与 I 对 σ、X 和 Z 的相似依赖性。而 α 的平均值对于土壤非均质性参数具有较大的置信区间，并且在干井入渗中起次要作用。这项研究为干井的选址、设计、安装和长期性能提供了宝贵的见解。