Estimation of Salt Water Upconing Using a Steady‐State Solution for Partial Completion of a Pumped Well
Estimation of Salt Water Upconing Using a Steady‐State Solution for Partial Completion of a Pumped Well
复制标题
使用稳态解对抽水井部分完井的盐水监测进行估计
作者：
S. P. Garabedian
针对含水层中的水位降深（水头）条件，开发了二维径向流方程的一种新的稳态解析解，该含水层具有恒定的透水性、顶部和底部无流条件、已知径向距离处的恒定水头条件以及部分完成的抽水井。通过与使用MODFLOW的数值模拟进行比较，对该解决方案的准确性进行了评估。然后使用该解决方案来估计在抽水井下发生的盐水-淡水界面的上升（上锥），并计算界面变得不稳定的临界抽水速率，允许盐水进入抽水井。盐水-淡水界面上升的分析假设对补给的上锥没有显著影响;使用为二维径向流条件下的补给开发的新稳态分析解的结果对该假设进行了测试和支持。在温和的抽水条件下，通过与使用SEAWAT进行的盐水-淡水界面位置数值模拟结果进行比较，对上锥分析结果的准确性进行了评估。该方程的结果还与已发表的数值锐界面模型的结果进行了比较，该模型应用于马萨诸塞州科德角的一个案例。这种比较表明，使用分析方法估计界面上升和最大允许泵送速率可能比从数值锐界面模型估计最大允许泵送速率和最大稳定界面上升保守。
A new steady‐state analytical solution to the two‐dimensional radial‐flow equation was developed for drawdown (head) conditions in an aquifer with constant transmissivity, no‐flow conditions at the top and bottom, constant head conditions at a known radial distance, and a partially completed pumping well. The solution was evaluated for accuracy by comparison to numerical simulations using MODFLOW. The solution was then used to estimate the rise of the salt water‐fresh water interface (upconing) that occurs under a pumping well, and to calculate the critical pumping rate at which the interface becomes unstable, allowing salt water to enter the pumping well. The analysis of salt water‐fresh water interface rise assumed no significant effect on upconing by recharge; this assumption was tested and supported using results from a new steady‐state analytical solution developed for recharge under two‐dimensional radial‐flow conditions. The upconing analysis results were evaluated for accuracy by comparison to those from numerical simulations using SEAWAT for salt water‐fresh water interface positions under mild pumping conditions. The results from the equation were also compared with those of a published numerical sharp‐interface model applied to a case on Cape Cod, Massachusetts. This comparison indicates that estimating the interface rise and maximum allowable pumping rate using the analytical method will likely be less conservative than the maximum allowable pumping rate and maximum stable interface rise from a numerical sharp‐interface model.