The Middle Columbia Lake Wallula watershed (HUC 17070101) covers an area of approximately 8,363 square miles in the Pacific Northwest region of the United States. It is characterized by a diverse hydrology system, ranging from snowmelt-fed streams and rivers to groundwater-fed wetlands. The watershed is home to the Walla Walla River, Yakima River, and several smaller tributaries. The snowpack in the region varies widely depending on elevation and terrain, with some areas receiving up to 500 inches of snowfall annually. Surface water quality in the watershed has been impacted by agricultural and urban runoff, leading to concerns about nutrient pollution and harmful algal blooms in reservoirs such as Lake Wallula. Climate trends in the region include increasing temperatures and changing precipitation patterns, with more winter precipitation falling as rain rather than snow. These changes have implications for water supply, agriculture, and ecosystem health in the watershed.