The Siletz-Yaquina Watershed, located in the central Oregon Coast Range, covers an area of approximately 800 square miles. It includes the Siletz and Yaquina Rivers and associated tributaries. The area experiences abundant precipitation, with an average annual rainfall of 90 inches, primarily falling as rainfall in the winter and spring months. The watershed has a highly variable hydrology with peak flows occurring during winter storms. Snowpack is generally not a significant contributor to the watershed's hydrology due to its proximity to the Pacific Ocean. Surface water quality is monitored, and the primary constituents of concern are temperature, sediment, and bacteria. The watershed includes several reservoirs, including Siletz Bay and Big Elk Lake, which are used for recreation and water storage. Interesting climatic facts about the area include the occasional occurrence of "atmospheric rivers," which are narrow bands of concentrated moisture that can result in significant precipitation events. Trends in the area include an increase in winter precipitation and a decrease in summer streamflows, likely due to climate change.