One of the primary means of addressing the depletion of aquifers supporting irrigated agriculture is to reduce pumping. In this work, we address the key question of how much data is needed to reliably predict the impact of pumping reductions. Previous studies have demonstrated the effectiveness of a simple water balance‐based approach for predicting the near‐term impact of changes in total pumping on changes in average water levels for areas ranging in size from 256 to 21,600 km2in the High Plains aquifer (HPA) in the state of Kansas in the central U.S. This method shows considerable promise as a management tool in the Kansas HPA and potentially other highly stressed aquifers. However, one characteristic that sets the Kansas HPA apart from many other aquifers is an abundance of data on both water levels, from a decades‐old annual water level measurement program, and annual pumping volumes, due to reporting requirements and regulatory oversight. Most regions will have considerably less information. This study investigates the impact of more limited data availability through random subsampling of the water level and water use data sets from Groundwater Management District 4 (GMD4) in northwest Kansas and GMD5 in south‐central Kansas. The results indicate that accurate estimates of net inflow and specific yield, the key parameters needed to predict near‐term aquifer responses to proposed pumping reductions, can be obtained with much sparser water level and water use data than are available in the Kansas HPA, as long as the data are not systematically biased.
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 (
- Award ID(s):
- 2108196
- NSF-PAR ID:
- 10371191
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Water Resources Research
- Volume:
- 58
- Issue:
- 7
- ISSN:
- 0043-1397
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Groundwater extraction in the United States (US) is unsustainable, making it essential to understand the impacts of limited water use on irrigated agriculture. To improve this understanding, we integrated a gridded crop model with satellite observations, recharge estimates, and water survey data to assess the effects of sustainable groundwater withdrawals on US irrigated agricultural production. The gridded crop model agrees with satellite‐based estimates of evapotranspiration (
R 2 = 0.68), as well as survey data from the United States Department of Agriculture (R 2 = 0.82–0.94 for county‐level production and 0.37–0.54 for county‐level yield). Using the optimistic assumption that groundwater extraction equals effective aquifer recharge rate, we find that sustainable groundwater use decreases US irrigated production of maize, soybean, and winter wheat by 20%, 6%, and 25%, respectively. Using a more conservative assumption of groundwater availability, US irrigated production of maize, soybean, and winter wheat decreases by 45%, 37%, and 36%, respectively. The wide range of simulated losses is driven by considerable uncertainty in surface water and groundwater interactions, as well as accounting for the many aspects of sustainability. Our results demonstrate the vulnerability of US irrigated agriculture to unsustainable groundwater pumping, highlighting the difficulty of expanding or even maintaining irrigated food production in the face of climate change, population growth, and shifting dietary demands. These findings are based on reducing pumping by fallowing irrigated farmland; however, alternate pumping reduction strategies or technological advances in crop genetics and irrigation could produce different results. -
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