The watershed extends from the town of Ruston on Commencement Bay south to DuPont, and east to Frederickson, covering about 149 square miles. Major lakes include American, Spanaway, Steilacoom, Gravelly, and Tule. Major streams are Chambers, Clover, Spanaway, Morey, Murray, Flett, Leach, Puget and Peach.
Seven municipalities, three military installations, and one drainage district, as well as Pierce County, have jurisdiction concerning water quality. The cities are: Tacoma, Lakewood, Fircrest, University Place, Steilacoom, DuPont, and Ruston. In 2018, the watershed's population was approximately 409,843 or 2,751 people per square mile.