Horn Judith E, Harter Thomas
Department of Land, Air, and Water Resources, University of California, Davis, CA 95616-8629, USA.
Ground Water. 2009 Mar-Apr;47(2):277-86. doi: 10.1111/j.1745-6584.2008.00521.x. Epub 2008 Nov 25.
Domestic wells in North America and elsewhere are typically constructed at relatively shallow depths and with the sand or gravel pack extending far above the intake screen of the well (shallow well seal). The source areas of these domestic wells and the effect of an extended gravel pack on the source area are typically unknown, and few resources exist for estimating these. In this article, we use detailed, high-resolution ground water modeling to estimate the capture zone (source area) of a typical domestic well located in an alluvial aquifer. Results for a wide range of aquifer and gravel pack hydraulic conductivities are compared to a simple analytical model. Correction factors for the analytical model are computed based on statistical regression of the numerical results against the analytical model. This tool can be applied to estimate the source area of a domestic well for a wide range of conditions. We show that an extended gravel pack above the well screen may contribute significantly to the overall inflow to a domestic well, especially in less permeable aquifers, where that contribution may range from 20% to 50% and that an extended gravel pack may lead to a significantly elongated capture zone, in some instances, nearly doubling the length of the capture zone. Extending the gravel pack much above the intake screen therefore significantly increases the vulnerability of the water source.
北美及其他地区的家用井通常建在相对较浅的深度，并且砂或砾石滤层延伸至井口进水筛管上方很远的位置（浅井密封）。这些家用井的水源地以及延伸的砾石滤层对水源地的影响通常是未知的，而且几乎没有资源可用于估算这些情况。在本文中，我们使用详细的高分辨率地下水模型来估算位于冲积含水层中的典型家用井的捕获区（水源地）。将各种含水层和砾石滤层水力传导率的结果与一个简单的解析模型进行比较。基于数值结果与解析模型的统计回归计算解析模型的校正因子。该工具可用于估算各种条件下家用井的水源地。我们表明，井口筛管上方延伸的砾石滤层可能对家用井的总入流量有显著贡献，尤其是在渗透性较差的含水层中，这种贡献可能在20%至50%之间，并且延伸的砾石滤层可能导致捕获区显著拉长，在某些情况下，捕获区长度几乎翻倍。因此，将砾石滤层延伸至进水筛管上方很远的位置会显著增加水源的脆弱性。
