The lake south of the Temescal Creek outlet lies in an open area at the mouth of its major tributary, the San Jacinto River, distantly bounded to the east by the Tuscany Hills and south of the river by the Sedco Hills both part of the range of the Temescal Mountains. Much of lake basin has been cut off from the lake and river by a flood-control levee, which only permits the isolated section to fill after an extremely large rainfall event raises the lake over the level of the overflow spillway, north of the baseball stadium.