The Rio Grande is a vital water source for the southwestern States of Colorado, New Mexico, and Texas and for northern Mexico. The river serves as the primary source of water for irrigation in the region, has many environmental and recreational uses, and is used by more than 13 million people including those in the Cities of Albuquerque and Las Cruces, New Mexico; El Paso, Texas; and Ciudad Juárez, Chihuahua, Mexico. However, concern is growing over the increasing gap between water supply and demand in the Upper Rio Grande Basin. As populations increase and agricultural crop patterns change, demands for water are increasing, at the same time the region is undergoing a decrease in supply due to drought and climate change.
Quantifying the impact of projected climate change on Rio Grande streamflow is difficult because of numerous anthropogenic influences on the hydrologic system. The conveyance and use of surface water in the Upper Rio Grande Basin are achieved through an engineered system of reservoirs, diversions, and irrigation canals designed to deliver water to agricultural, municipal, and industrial users, who greatly reduce the cumulative volume of water in the river. For example, streamflow at Fort Quitman, Tex., the southernmost point of the Upper Rio Grande Basin, has undergone a 95-percent reduction in flow relative to the river’s native state, and some stretches of the river can intermittently go dry. Because streamflow in the basin is highly altered, disentangling the impacts of climate change and changes in streamflow due to anthropogenic influences such as dams, diversions, and other forms of water use is difficult. Therefore, a model of naturalized flow was developed to determine to what degree changes in streamflow can be attributed to potential changes in future temperature and precipitation without quantifying future changes in anthropogenic influences. This study, conducted by the U.S. Geological Survey in cooperation with the South Central Climate Adaptation Science Center and the U.S. Army Corps of Engineers, included the development and calibration of a watershed model of the Upper Rio Grande Basin using the Precipitation-Runoff Modeling System to simulate naturalized streamflow conditions for historical and future time periods.
