The Upper Cooper Slough Basin is a tributary to Boxelder Creek and Lower Cooper Slough. It encompasses 26 square-miles and extends north from the Larimer and Weld Canal and west of Interstate 25. Most of the basin is currently farmland except for the Anheuser-Busch brewery site. The southern portion of the basin within the City of Fort Collins Growth Management Area is experiencing rapid urbanization, especially with housing developments.

Stormwater within this basin flows generally from north to south, with runoff ultimately being captured by the Larimer and Weld Canal. During large storm events, runoff spills into Lower Cooper Slough from the Larimer and Weld Canal. 

Located on the west side of the basin, the No. 8 Ditch runs north to south and is a primary conveyance of stormwater to the Larimer and Weld Canal. When the canal exceeds capacity, stormwater spills out of the ditch to the southeast combining with runoff from the north, often overtopping the Colorado and Southern Railroad and into the Larimer and Weld Canal.