Transitions from irrigated to dryland agriculture in the Ogallala Aquifer: Land use suitability and regional economic impacts

Authors: DEINES, JILLIAN - Stanford University; SCHIPANSKI, MEAGAN - Colorado State University; GOLDEN, BILL - Kansas State University; ZIPPER, SAMUEL - University Of Kansas; NOZARI, SOHEIL - Colorado State University; Rottler, Caitlin; GUERRERO, BRIDGET - West Texas A & M University; SHARDA, VAISHALI - Kansas State University

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2020
Publication Date: 2/14/2020
Citation: Deines, J.M., Schipanski, M.E., Golden, B., Zipper, S.C., Nozari, S., Rottler, C.M., Guerrero, B., Sharda, V. 2020. Transitions from irrigated to dryland agriculture in the Ogallala Aquifer: Land use suitability and regional economic impacts. Agricultural Water Management. 233:106061. https://doi.org/10.1016/j.agwat.2020.106061.
DOI: https://doi.org/10.1016/j.agwat.2020.106061

Interpretive Summary: Many agricultural communities depend on groundwater irrigation as a supplemental or primary water source. However, groundwater resources are finite, and groundwater depletion can make continued irrigation inviable. Studies often assume that irrigated cropland will transition uniformly to dryland crop production as irrigation water becomes less available. However, irrigation has allowed crops to be grown across a wider range of soil and climate conditions than can support dryland crop production. Here, we tested the agronomic and economic importance of this assumption by mapping the anticipated future irrigation depletion across the Ogallala or High Plains Aquifer (USA). We then determined whether these lands would most likely transition to dryland agriculture or pasture. We found that 24%of currently irrigated lands in the High Plains Aquifer will be unable to support irrigated agriculture by 2100 due to aquifer depletion. Additionally, 13% of these areas are not suitable for dryland crop production due to low quality soils. To quantify the farm-scale and regional-scale economic importance of soil suitability, we selected one county from each of six Ogallala states and tested farm and community-scale economic outcomes (revenue and value added, respectively) with and without consideration of soil suitability. We found that not accounting for soil suitability led to an overestimate of economic benefits in transitioned land by 10-40%. Our analyses highlight the importance of considering climate and soil in planning for future land use trajectories. Community and regional land use planners need to be aware of the possibility that irrigated cropland may transition to non-irrigated pasture production rather than dryland crop production, which can have significant economic impacts.

Technical Abstract: Many agricultural communities depend on groundwater irrigation as a supplemental or primary water source. However, groundwater resources are finite, and groundwater depletion can make continued irrigation inviable. When modeling the economic impacts of future aquifer decline, studies often assume that irrigated cropland will transition uniformly to dryland crop production. However, irrigation has allowed crops to be grown across a wider range of soil and climate conditions than can support dryland crop production. Here, we test the agronomic and economic importance of this assumption by mapping the spatiotemporal distribution of anticipated future irrigation depletion across the Ogallala or High Plains Aquifer (USA) at annual, 30 m resolution. We then develop a land use suitability model to determine whether these lands would transition to dryland agriculture or pasture predict non-irrigated land use in these areas. We find that 22,000 km2 (24%) of currently irrigated lands in the High Plains Aquifer will be unable to support irrigated agriculture by 2100, and 13% of these areas are not suitable for dryland crop production due to low quality soils and will therefore more likely transition to pasture. To quantify the farm-scale and regional-scale economic importance of soil suitability, we selected one county from each of six Ogallala states and modeled farm and community-scale economic outcomes (revenue and value added, respectively) with and without consideration of soil suitability. We find that not accounting for soil suitability leads to an overestimate of economic benefits in transitioned land by 10-40%, with variability across counties primarily driven by the distribution of soil suitability, dryland crop mix, and local economic factors. Our analyses highlight the importance of considering biophysical constraints in planning for future land use trajectories. Community and regional land use planning needs to incorporate the possibility that irrigated cropland may transition to non-irrigated pasture production rather than dryland crop production, which can have significant biophysical and economic impacts.