South Fork Tolt Reservoir is located near Carnation, WA in King County, Washington. The reservoir was created in the 1960s to provide water for the growing population of nearby cities. It is fed by surface flow from the Tolt River and snowpack providers.

The hydrology of the reservoir is influenced by the South Fork Tolt River, which flows into the reservoir from the west. The reservoir provides water to the city of Seattle, and it also supports agricultural and recreational activities in the area.

The reservoir has a capacity of 18,000 acre-feet and is approximately 80% full during the summer months. It provides water for irrigation and drinking water for the surrounding communities.

In terms of recreational activities, the reservoir is popular for fishing, boating, and hiking. The surrounding area is also home to several campgrounds and picnic areas, making it a popular destination for outdoor enthusiasts.