The North Fork Elkhorn Watershed (HUC 10220002) covers approximately 498 square miles in northeastern Oregon. The hydrology of the watershed is mainly influenced by the Blue Mountains and is characterized by a semi-arid climate with an average annual precipitation of 15-25 inches. The snowpack in the watershed is vital for the surface water supply for irrigation and domestic use. The surface water in the watershed is mainly from the North Fork Elkhorn River and its tributaries. The biggest reservoir in the watershed is the Mason Dam Reservoir, which provides irrigation water to the surrounding agricultural lands. Interesting climatic facts and trends include the increase in average temperatures and a decrease in snowpack in recent years, leading to decreased surface water availability. The watershed is also prone to wildfires due to the dry and warm climate.