The Newport Bay Watershed covers an area of approximately 142 square miles and is located in Orange County, California. It is a low-lying coastal plain that is primarily composed of urban and suburban land uses. The watershed is defined by the Santa Ana River to the north and the Pacific Ocean to the south. The hydrology of the Newport Bay Watershed is heavily influenced by urbanization and stormwater runoff. The area experiences a Mediterranean climate with mild, wet winters and hot, dry summers. Snowpack is not a significant factor in this region. Surface water in the watershed includes Newport Bay, Upper Newport Bay, and several smaller tributaries. These water bodies are heavily impacted by urbanization and pollution from stormwater runoff. Reservoir constituents in the Newport Bay Watershed are primarily composed of urban runoff and pollutants such as oil, grease, and heavy metals. The watershed is home to several endangered species, including the California Least Tern and the Pacific Green Sea Turtle. Climatic trends in the Newport Bay Watershed include increasing temperatures and decreased precipitation, which may exacerbate the impacts of urbanization and pollution on surface water quality. However, ongoing efforts to manage stormwater runoff and preserve natural habitats may help to mitigate these impacts in the future.