Butler James J, Zhan Xiaoyong, Zlotnik Vitaly A
Kansas Geological Survey, 1930 Constant Avenue, Campus West, University of Kansas, Lawrence, KS 66047, USA.
Ground Water. 2007 Mar-Apr;45(2):178-86. doi: 10.1111/j.1745-6584.2006.00272.x.
The impact of ground water pumping on nearby streams is often estimated using analytic models of the interconnected stream-aquifer system. A common assumption of these models is that the pumped aquifer is underlain by an impermeable formation. A new semianalytic solution for drawdown and stream depletion has been developed that does not require this assumption. This solution shows that pumping-induced flow (leakage) through an underlying aquitard can be an important recharge mechanism in many stream-aquifer systems. The relative importance of this source of recharge increases with the distance between the pumping well and the stream. The distance at which leakage becomes the primary component of the pumping-induced recharge depends on the specific properties of the aquifer, aquitard, and streambed. Even when the aquitard is orders of magnitude less transmissive than the aquifer, leakage can be an important recharge mechanism because of the large surface area over which it occurs. Failure to consider aquitard leakage can lead to large overestimations of both the drawdown produced by pumping and the contribution of stream depletion to the pumping-induced recharge. The ramifications for water resources management and water rights adjudication can be significant. A hypothetical example helps illustrate these points and demonstrates that more attention should be given to estimating the properties of aquitards underlying stream-aquifer systems. The solution presented here should serve as a relatively simple but versatile tool for practical assessments of pumping-induced stream-aquifer interactions. However, this solution should not be used for such assessments without site-specific data that indicate pumping has induced leakage through the aquitard.
通常使用相互连通的河流 - 含水层系统分析模型来估算地下水抽取对附近溪流的影响。这些模型的一个常见假设是，被抽水的含水层下面有一层不透水地层。现已开发出一种新的关于水位下降和溪流枯竭的半解析解，该解不需要这个假设。这个解表明，通过下层隔水层的抽水诱发水流（渗漏）在许多河流 - 含水层系统中可能是一种重要的补给机制。这种补给源的相对重要性随着抽水井与溪流之间的距离增加而增大。渗漏成为抽水诱发补给的主要组成部分时的距离取决于含水层、隔水层和河床的具体特性。即使隔水层的透水性比含水层小几个数量级，由于其发生渗漏的表面积很大，渗漏仍可能是一种重要的补给机制。不考虑隔水层渗漏可能导致对抽水产生的水位下降以及溪流枯竭对抽水诱发补给的贡献的大幅高估。这对水资源管理和水权裁决的影响可能很大。一个假设的例子有助于说明这些要点，并表明应更加重视估算河流 - 含水层系统下方隔水层的特性。这里给出的解应作为一种相对简单但通用的工具，用于实际评估抽水诱发的河流 - 含水层相互作用。然而，如果没有特定场地数据表明抽水已诱发通过隔水层的渗漏，此解不应用于此类评估。
