Climate Change Impacts of Irrigation on the Central High Plains

Abstract:

Since the 1940s, the High Plains Aquifer (HPA) has been pivotal for irrigation over the Central High Plains (CHP), a region spanning parts of five states in the central U.S.. Today after decades of over-pumping, many areas of the CHP are no longer able to irrigate due to localized depletion of the HPA. With a range of global climate models predicting an increase in temperature and decrease in growing-season precipitation for the CHP, demand for irrigation is likely to increase and exacerbate drawdown and depletion of the aquifer. Here we apply the Landscape Hydrology Model (LHM) coupled with the crop simulation model SALUS to simulate irrigation water use in response to historical climate and land use. This model is validated using historical groundwater levels. We then simulate future climate scenarios to predict how irrigation demand and water availability will alter the hydrology of the CHP. This study provides a predictive relationship of future irrigation demand linked to both climate change and agricultural management, and presents a modeling approach to answer two questions: How will future climate change affect irrigation demand? How will climate change and irrigation demand affect groundwater availability for the future? Different climate scenarios based on the representative concentration pathways (RCPs) are used to simulate the impact of different projected future climate conditions through the year 2100. By examining predicted groundwater levels along with saturated thickness we analyze where irrigation is likely to be viable in the future and compare this to current irrigation extent.