Quantifying the Impact of Lagged Hydrological Responses on the Effectiveness of Groundwater Conservation. Issue 7 (11th July 2022)

• Record Type: Journal Article
• Authors: Glose, Thomas J.; Zipper, Sam; Hyndman, David W.; Kendall, Anthony D.; Deines, Jillian M.; Butler, James J.
• Is Part Of: Water resources research. Volume 58:Issue 7(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-07-11
• Subjects: numerical modeling -- lagged processes -- groundwater conservation -- pumping reductions -- irrigation practices; Hydrology -- Periodicals; 333.91
• DOI: 10.1029/2022WR032295
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: 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. Key Points: The long‐term effectiveness of pumping reduction‐based groundwater conservation is dependent on lagged processes Vertical hydraulic conductivity ( K Z ) controls if lagged responses are lateral‐flow dominated or recharge‐dominated Ignoring lagged processes overestimates aquifer lifetime by 32 and 133 years in lateral‐flow and recharge‐dominated settings, respectively