The future of irrigation on the U.S. Great Plains

Authors: Evett, Steven - Steve; Colaizzi, Paul; Oshaughnessy, Susan; LAMM, FREDDIE - Kansas State University; Trout, Thomas; KRANZ, WILLIAM - University Of Nebraska

Submitted to: Proceedings of the Central Plains Irrigation Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/12/2014
Publication Date: 2/25/2014
Citation: Evett, S.R., Colaizzi, P.D., Oshaughnessy, S.A., Lamm, F.R., Trout, T.J., Kranz, W.L. 2014. The future of irrigation on the U.S. Great Plains. Proceedings of the Central Plains Irrigation Conference [abstract].

Interpretive Summary: The future of irrigation on the United States Great Plains was examined through the lens of past changes in water supply and innovations in irrigation technology, management and agronomy. The innovations have greatly increased the efficiency of water application and use, and the agricultural productivity of the Great Plains. Scientists at the USDA-ARS Conservation & Production Research Laboratory, Bushland, Texas, teamed with agricultural scientists and engineers from Colorado, Kansas and Nebraska to analyze the history of irrigation agriculture through the 1900s to the present day. The team also examined the changes in water stored in the High Plains Aquifer, which is the region’s principle supply for irrigation water. The aquifer has hardly been impacted in Nebraska, despite large increases in irrigated area. Greatly increased irrigation efficiency has played a role in this, but so also has the recharge to the aquifer from the Nebraska Sand Hills and from rivers crossing the state. The outlook for irrigation is less positive in SW Arkansas, SE Colorado and the Panhandles of Oklahoma and Texas. The aquifer in these regions is recharged at rates much less than current pumping, and the aquifer is declining as a result. Improvements in irrigation technology and management plus changes in crops grown have made irrigation ever more efficient. There is good reason to expect that future research and development on the part of federal and state researchers and private companies, often in concert, will continue to improve the efficiency of irrigated agriculture. Public policy changes will also play a role in regulating consumption and motivating on-farm efficiency improvements. Water supplies, while finite, will be stretched much further than projected by some who look only at past rates of consumption. Thus, irrigation will continue to be important economically for an extended period. Sustaining irrigation is crucial to sustained productivity of the Great Plains “bread basket” because irrigation doubles the efficiency with which water is turned into crop yields compared with what can be attained with precipitation alone.

Technical Abstract: In the Great Plains, soil and water conservation is being achieved in both dryland and irrigated agricultural systems, and increasingly in combinations of these systems. Limiting tillage has increased the retention of crop residues on the surface and has reduced the evaporative loss of water, making more water available for plant growth and yield formation in both dryland and irrigated systems. Irrigation application efficiencies have steadily improved with the move from gravity to pressurized systems and with the ongoing improvements in reduction of evaporative losses in pressurized systems. Efficiency increases also resulted from the introduction of alternative furrow irrigation, and LEPA and drip irrigation technologies. Improved irrigation scheduling methods and technologies, including automation, have reduced losses of water to runoff and deep percolation, and have also reduced yield loss due to under irrigation, leading to overall improvement in water use efficiency. The future of the Great Plains has often been viewed as tied to only one moving target: the steady decline of the aquifer. Recently, the moving target of climate change has been added to the perspective, reducing expectations for precipitation and increasing the expectations for evaporative demand due to warming, particularly in the southern half of the Great Plains. Two other moving targets have been largely ignored in predictions of the future, however, and they are key to understanding what is to come. One is the moving target of improving irrigation technologies coupled with improving cultivars to steadily improve crop water productivity, making irrigated agriculture economically sustainable with decreasing water supply. However, improvements in irrigation management, methods and technologies can only improve the efficiency with which water is used for crop production; they cannot reduce pumping of the mostly non-renewable water resource in the southern part of the High Plains aquifer. Thus, the fourth key moving target is water policy. In the end, either the aquifer will be pumped until supplies economically obtainable for irrigation are exhausted, or the people of the Plains will decide to institute policies and regulations that limit pumping to sustainable levels. Fortunately, the sustainability of irrigated agriculture with reduced water supplies has been greatly increased due to advances in irrigation application and management methods resulting from combined state, federal and private research and development efforts. This should allow for a longer and smoother transition to a less irrigated agriculture in the U.S. Great Plains.