WATER SCARCITY
scientific footing? In a recent paper, “Aquifer depletion exacerbates agricultural drought losses in the US High Plains,” we’ve tried to do just that (
https://rdcu.be/ dv1rT). The paper was published in Nature Water and supported by funding from USDA-Office of the Chief Economist, the Daugherty Water for Food Global Institute and Innovate UK. Taro Mieno, an associate professor at the University of Nebraska- Lincoln, is the lead author of the paper. Tim Foster, senior lecturer at the University of Manchester, and Shunkei Kakimoto, currently a doctoral candidate at the University of Minnesota, are co-authors. I’ve been fortunate to collaborate with Taro and Tim on multiple projects over the last decade.
How aquifer depletion exacerbates agricultural drought losses
In our paper, we looked at 30 years of historical crop yield and production data for a portion of the High Plains region, together with relevant hydrologic and climate data. Our statistical analysis demonstrated that over a large area, and over time, aquifer conditions
26 Irrigation TODAY | Spring 2024
fundamentally affect growers’ ability to reliably buffer crops against the impact of drought. Our results show that thick aquifers (hundreds of feet or more) can effectively and consistently mitigate the impacts of drought on crop yields. During droughts, crop yields for non-irrigated land above thick aquifers drop considerably relative to wet years, as we’d expect. Those fields have no access to water, after all. On the other hand, crop yields don’t drop at all between wet and drought years for irrigated land above thick aquifers. For thin aquifers, of around 100 feet thickness or less, yield reductions during droughts occur on irrigated land even for small crop water deficits. The available water simply can’t keep up with crop water needs.
Overall, our results show that the depletion of groundwater increases the physical and economic vulnerability of
agricultural production to drought risks, now and in the future. Moreover, the impact of thinning an aquifer on growers’ ability to mitigate drought risk is nonlinear. As aquifers thin, agricultural production becomes progressively more and more risky, leading expected crop yields to drop first gradually, and then suddenly.
What’s happening from an economic perspective? There are two effects to consider. First, as an aquifer thins, the lift required to bring water to the surface will increase. This means that energy requirements and production costs will increase and irrigation will become less profitable as aquifers deplete. This effect is roughly linear: if the lift required to bring water to surface doubles, then the energy needed to do so will also more or less double. All by itself, this effect should reduce the sale and rental values
OVERALL, OUR RESULTS SHOW THAT THE DEPLETION OF GROUNDWATER INCREASES THE PHYSICAL AND ECONOMIC VULNERABILITY OF AGRICULTURAL PRODUCTION TO DROUGHT RISKS, NOW AND IN THE FUTURE.
irrigationtoday.org
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