The Big Wood Watershed, HUC 17040219, covers an area of approximately 1,694 square miles in south-central Idaho. The watershed is characterized by a combination of mountainous terrain and arid valleys with a diverse ecosystem ranging from sagebrush steppe to alpine forest. The hydrology of the watershed is largely influenced by snowmelt runoff, which provides the majority of surface water during the summer months. The specific snowpack varies greatly depending on elevation and location, with the highest elevations receiving the most snow. Surface water in the watershed is largely used for irrigation and other agricultural purposes. Reservoirs in the watershed often contain high levels of sediment due to erosion from the surrounding landscape. Interesting climatic facts include the area experiencing an average of 230 sunny days per year and experiencing extreme temperature fluctuations between summer and winter. In recent years, the watershed has faced challenges from drought and decreasing snowpack levels.