The Lower Dan Watershed (HUC 03010104) covers an area of approximately 2,800 square miles in central and eastern Oregon. Hydrologically, the watershed is characterized by its location in the rain shadow of the Cascade Mountains, which results in a semi-arid climate. The watershed receives most of its precipitation as snow in the winter and early spring months, which contributes to a significant snowpack during those seasons. Surface water in the watershed is primarily sourced from the Lower Deschutes River, which runs through the middle of the watershed before flowing into the Columbia River. Reservoirs in the watershed include Lake Billy Chinook and Round Butte Reservoir, which are used for hydroelectric power generation and recreation. Interesting climatic facts and trends include a long-term trend of increasing temperatures and decreasing snowpack, which has implications for water availability and wildfire risk in the region.