The Balch subwatershed extends from near NW Skyline Boulevard to the Willamette River. Balch Creek flows through from the crest of the West Hills down the canyon containing NW Cornell Road. It enters a large concrete box culvert at the lower end of Macleay Park and remains underground from there to the river. The upper portion of the subwatershed is mostly wooded, including parts of Forest Park, Macleay Park, and the 180-acre Audubon Society Nature Sanctuary. The lower portion of the subwatershed includes the site of historic Guilds Lake, filled in the early 1900s to create land for industrial development.