Many irrigated agricultural areas seek to prolong the lifetime of their groundwater resources by reducing pumping. However, it is unclear how lagged responses, such as reduced groundwater recharge caused by more efficient irrigation, may impact the long-term effectiveness of conservation initiatives. Here, we use a variably saturated, simplified surrogate groundwater model to: (a) analyze aquifer responses to pumping reductions, (b) quantify time lags between reductions and groundwater level responses, and (c) identify the physical controls on lagged responses. We explore a range of plausible model parameters for an area of the High Plains aquifer (USA) where stakeholder-driven conservation has slowed groundwater depletion. We identify two types of lagged responses that reduce the long-term effectiveness of groundwater conservation, recharge-dominated and lateral-flow-dominated, with vertical hydraulic conductivity (K_Z) the major controlling variable. When high K_Z allows percolation to reach the aquifer, more efficient irrigation reduces groundwater recharge. By contrast, when low K_Z impedes vertical flow, short term changes in recharge are negligible, but pumping reductions alter the lateral flow between the groundwater conservation area and the surrounding regions (lateral-flow-dominated response). For the modeled area, we found that a pumping reduction of 30% resulted in median usable lifetime extensions of 20 or 25 years, depending on the dominant lagged response mechanism (recharge- vs. lateral-flow-dominated). These estimates are far shorter than estimates that do not account for lagged responses. Results indicate that conservation-based pumping reductions can extend aquifer lifetimes, but lagged responses can create a sizable difference between the initially perceived and actual long-term effectiveness.

中文翻译：

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量化滞后水文响应对地下水保护有效性的影响

许多灌溉农业区寻求通过减少抽水来延长其地下水资源的寿命。然而，尚不清楚滞后反应（例如更有效的灌溉导致地下水补给减少）可能如何影响保护举措的长期有效性。在这里，我们使用可变饱和的简化替代地下水模型来：（a）分析含水层对抽水减少的响应，（b）量化减少和地下水位响应之间的时间滞后，以及（c）确定滞后响应的物理控制。我们为高平原含水层（美国）的一个地区探索了一系列合理的模型参数，在该地区，利益相关者驱动的保护减缓了地下水枯竭。我们确定了两种类型的滞后反应，它们会降低地下水保护的长期有效性，K _Z ) 主要控制变量。当高K _Z允许渗透到达含水层时，更有效的灌溉会减少地下水补给。相比之下，当低K _Z阻碍垂直流动，补给的短期变化可以忽略不计，但抽水减少会改变地下水保护区和周边地区之间的横向流动（横向流动主导的响应）。对于建模区域，我们发现抽水减少 30% 导致中位可用寿命延长 20 或 25 年，这取决于主要的滞后响应机制（再充电与侧流为主）。这些估计值比不考虑滞后响应的估计值要短得多。结果表明，基于保护的抽水减少可以延长含水层的寿命，但滞后的反应会在最初感知的和实际的长期有效性之间产生相当大的差异。