The Rose Creek watershed includes Rose Canyon, Marian Bear Park, and areas downstream as far as Mission Bay. A watershed is a geographic area that drains to a common body of water through creeks, rivers and the storm drain system. Rose Creek is the main fresh water tributary of Mission Bay. It’s watershed is a 23,427-acre area. It includes San Clemente Creek, which flows through Marian Bear Park and into Rose Creek at the I-5/52 intersection. The storm water and irrigation run-off from all the highways, streets, and developed areas in this watershed end up in Rose Creek. Think about it.