Sensitivity of Irrigation Water Balance to Climate Change in the Great Plains of Colorado

Abstract

The possible effects of regional climatic changes on irrigation water supply and demand in Colorado's Arkansas River basin are investigated using a composite model. Two models are developed and applied to the region to estimate the effects of climate change on irrigation water balance. The first model is an artificial neural network developed to estimate the effects of climatic changes on water supplies for irrigation in the region. The second model is a consumptive use model developed to estimate the effects of climate change on irrigation water demand. Both models were applied to baseline and two transient climatic scenarios generated at 0.5 resolution from the following General Circulation Models: the HAD from the Hadley Centre for Climate Prediction and Research, and the CCC from the Canadian Climate Centre. Surface water supply and evapotranspiration were estimated for five subareas at 0.5 resolution and then spatially integrated to calculate a basin-wide irrigation water balance. Projections by the two models were used to evaluate the responses of the irrigation balance to climatic changes. Under the CCC scenario, water supplies are not expected to be sufficient to satisfy the demand for irrigation water in each month during the growing season, except for April. Under the HAD scenario, which is wetter and cooler than the CCC scenario, water supplies increase to meet demand or do not differ from present conditions. However, the positive results of the HAD scenario rely on the availability of water storage facilities.