The Grand Canyon Watershed (HUC 15010002) covers an area of approximately 16,200 square miles in northern Arizona. The region is characterized by dry, arid conditions, with most precipitation occurring in winter months. Snowpack accumulation in the winter is critical to the hydrology of the watershed, with snowmelt providing the majority of surface water during the spring and summer months. The watershed includes the Colorado River, which supplies water to millions of people and irrigates agricultural fields in the Southwest. The river also provides hydroelectric power and recreation opportunities. The watershed is home to several large reservoirs, including Lake Powell and Lake Mead, which store water for use during times of drought. Climate change is expected to have a significant impact on the hydrology of the watershed, with increasing temperatures resulting in reduced snowpack and changes in precipitation patterns.