Modeling climate change impacts on blue, green, and grey water footprints and crop yields in the Texas High Plains, USA

Authors: CHEN, YONG - Texas A&M University; Marek, Gary; MAREK, THOMAS - Texas A&M Agrilife; PORTER, DANA - Texas A&M Agrilife; Brauer, David; SRINIVASAN, R - Texas A&M University

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/10/2021
Publication Date: 10/22/2021
Citation: Chen, Y., Marek, G.W., Marek, T.H., Porter, D.O., Brauer, D.K., Srinivasan, R. 2021. Modeling climate change impacts on blue, green, and grey water footprints and crop yields in the Texas High Plains, USA. Agricultural and Forest Meteorology. 310. Article 108649. https://doi.org/10.1016/j.agrformet.2021.108649.
DOI: https://doi.org/10.1016/j.agrformet.2021.108649

Interpretive Summary: Declining well capacities and potential climate change have led to concerns about the future of irrigated crop production in the Texas High Plains. Although the effects of climate change on agriculture are largely unknown, simulation modeling can be useful for comparing crop production under future climate scenarios. Scientists from ARS (Bushland, Texas) and Texas A&M AgriLife simulated irrigated production of corn, sorghum, and winter wheat using a Soil and Water Assessment Tool (SWAT) model equipped with an improved auto-irrigation algorithm using an ensemble of future climate projections for precipitation, temperature, and CO2. Overall, results indicated reductions in yield for both corn and sorghum, primarily due to reduced crop water use and concomitantly decreased plant growth due to previously reported effects increased atmospheric CO2 concentrations of stomatal opening. As such irrigation requirements were reduced for all crops including winter wheat. However, results showed increased yields for irrigated winter wheat as the effects of increased CO2 was offset by avoiding heat stress, due to overwinter and early spring growing season. Simulated surface runoff values varied greatly, having a high degree of uncertainty.

Technical Abstract: Simulating the impacts of future climate change on water footprints and crop production allows for selecting alternative crops for mitigating climate change effects. In this study, climate change impacts on irrigated grain corn, grain sorghum, winter wheat, and dryland (rainfed) winter wheat in the Palo Duro watershed of the Texas High Plains were assessed using an improved Soil and Water Assessment Tool (SWAT) model with an enhanced irrigation representation of management allowed depletion (MAD) irrigation scheduling. Climate change analyses in this study used the Coupled Model Intercomparison Project Phase 5 (CMIP5) climate projections of 11 General Circulation Models (GCMs) under four Representative Concentration Pathway (RCP) emission scenarios of RCP2.6, 4.5, 6.0, and 8.5 during two 30-year periods of the middle (2040-2069) and end (2070-2099) of the 21st century to compare to a baseline period of 1970-1999. For the irrigated summer crops of corn and sorghum, all 11 GCMs predicted the reductions of future irrigation, crop evapotranspiration (ETc), and yields compared to the baseline period. According to an ensemble of 11 GCMs, the simulated reductions in average annual irrigation, ETc, and yield for the irrigated corn were 63, 34, and 13 percent, respectively, at the end of the 21st century under the severe emission scenario of RCP8.5. Those values were 80, 34, and 34 percent under the irrigated sorghum land use. As for the irrigated winter wheat, the decreases in future irrigation and ETc were also identified in all GCMs relative to the baseline period. However, irrigated wheat yields were increased in the future climate. The changes in dryland wheat ETc were consistent with the rainfall variation under all climate change scenarios. Generally, the future climate could benefit the dryland wheat yields. A large uncertainty was found for the surface runoff simulations under both irrigated and dryland wheat according to various GCMs.