While the impact of climate change on crop yields has been extensively studied, the quantification of water shortages on irrigated crop yields has been more challenging due to the complexity of the system to consider. By combining a water model and a crop model within the MIT Integrated Global System Model (IGSM) framework, an integrated assessment of the effects of alternative climate policy scenarios on irrigated crop yields is applied to the United States. In this analysis, we consider the effect of water shortage for irrigation on the three most important crops for the U.S.: maize, soybean and spring wheat. Projected impacts for the mid-century are estimated under two greenhouse gas emission scenarios and two climate change patterns. We find that water shortage for irrigation is expected to reduce irrigated crop yields in the Northern and Southern Plain, with the largest decrease expected for maize.