The Umatilla Watershed (HUC 17070103) spans over 2,800 square miles in northeastern Oregon and southeastern Washington. The watershed is primarily arid and semi-arid with a temperate climate. The area receives most of its precipitation in the winter months, with snowpacks accumulating in the mountains. The Umatilla River is the primary source of surface water in the area, and supports a diverse range of fish and wildlife species. The river also feeds into several reservoirs, including the McKay Reservoir and the Cold Springs Reservoir. The watershed is also home to several interesting climatic facts, including the occasional occurrence of thunderstorms during the winter months. Trends in the area include increasing temperatures and decreasing snowpacks, which can have significant impacts on the hydrology and ecology of the watershed.