According to the Turtle Creek Watershed Association, "The Turtle Creek watershed is situated in western Westmoreland County and eastern Allegheny County in southwestern Pennsylvania. Sixty-six percent of the watershed is situated in Westmoreland County, 34 percent in Allegheny County. Turtle Creek flows west from its source in Delmont, Westmoreland County to its mouth where it enters the Monongahela River in North Versailles Township, Allegheny County. The watershed drains a catchment area of 147.41 square miles (381.79 km2) that includes forest, farmland, industry, abandoned mined lands, urban, and suburban residential communities. 33 municipalities are located within the Turtle Creek watershed. The lower watershed lies between a heavily urbanized area between the cities of Pittsburgh and McKeesport."
Subwatersheds include the following (according to the Turtle Creek Watershed Association):
Taken directly from Turtle Tracks, Fall 2000. The Turtle Creek Watershed Association.
You can access more information about the Turtle Creek watershed at [1]