Water available for irrigation will be affected by climate and increasing demand from other sectors, with consequences for energy-water-land interactions.
Climate change poses a threat to global food production, with some regions under heightened risk to droughts, flooding and other disruption. One powerful countermeasure is irrigation: globally production on a hectare of irrigated land is 2.7 times that on dry land. The future of irrigation, however, depends on the continued availability of significant volumes of fresh water. Food production now accounts for 70% of global freshwater use, and many areas are already water stressed. Climate change, together with increased demand from other sectors, could exert further pressure on irrigation capabilities by altering the volume and geographical distribution of available water resources. Warmer temperatures would also increase evapotranspiration, and water demands of irrigated crops.
Model simulations under a business-as-usual scenario of greenhouse gas emissions indicate that climate change and economic development increase water shortages and reduce irrigated yields in some regions of the US (particularly the Southwest) where irrigation is not sustainable, and for specific crops including cotton and forage. These developments would require adaptive measures that range from growing less irrigation-intensive crops to relocating croplands, with implications for land use elsewhere, indicating the need for comprehensive integrated assessment of human-earth system interactions.
A critical component of water-energy-land interactions is irrigation for crop production. A changing climate and demand from other sectors for water, including for energy production, may limit water availability for irrigation, resulting in reduced crop yields. To investigate these complex, multi-sectoral interactions, researchers at the MIT Joint Program on the Science and Policy of Global Change developed a unique and comprehensive method to quantify the impact of water stress on irrigation while accounting for changes in water resources and competing uses from all US economic sectors. Incorporating a crop-yield reduction module and water-resources model (representing 99 river basins) into the MIT Integrated Global System Modeling (IGSM) framework (an integrated assessment model linking a global economic model to an Earth-system model), they assessed the effects of climate change and economic development on water availability for irrigation in the US as well as subsequent impacts on crop yields by 2050. The researchers found that under a business-as-usual scenario, climate change and economic development may increase water shortages and reduce irrigated yields in some regions (particularly the Southwest) where irrigation is not sustainable, and for specific crops (e.g., cotton and forage). Additional simulations show that greenhouse gas mitigation can alleviate the effect of water stress on irrigated crop yields. The response of crop yields to climate change and water stress suggests that some level of adaptation will be feasible, like relocating croplands to regions with sustainable irrigation or switching to less irrigation-intensive crops or more water-efficient irrigation technology.
BER PM Contact
MIT Joint Program on the Science and Policy of Global Change
This research was funded by the U.S. Environmental Protection Agency, the U.S. Department of Energy Office of Science, and other government, industry and foundation sponsors of the MIT Joint Program.
Blanc, E., J. Caron, C. Fant and E. Monier, 2017: Is Current Irrigation Sustainable in the United States? An Integrated Assessment of Climate Change Impact on Water Resources and Irrigated Crop Yields, Earth’s Future, doi:10.1002/2016EF000473.
Photo: Cotton growing at Chippokes Plantation State Park (Source: Virginia State Parks)