Mossyrock Dam & Reservoir

The reservoir backed up behind Mossyrock Dam forms Riffe Lake.

Riffe Lake

Riffe Lake (pronounced to rhyme with "life") at full elevation covers 11,830 acres. The lake was named after a small pioneering community that was covered when the lake was formed.

The reservoir serves multiple purposes besides power generation, It is a popular recreation destination, particularly in the summer and fall. During winter and spring the level of the reservoir is lowered to provide space to help manage down-river flooding. During the summer months water is gradually released to provide supplemental river flows for the benefit of fish habitat.

Tacoma Power operates two very popular campgrounds by Riffe Lake. Mossyrock Park is on the southwest shore near the dam. Taidnapam Park is on the east end where the Cowlitz River flows into Riffe Lake.

Tacoma Power provides three boat launches to Riffe Lake. At the southwest end of the Lake is the Mossyrock Park boat launch. At the northeast end of the lake, near Glenoma and State Highway 12, is the Kosmos boat launch. And at the southeast end of the lake is the Taidnapam Park boat launch.The boat ramp at Mossyrock Park is open throughout the year. The launches at Taidnapam Park and Kosmos are open during summer months when the lake is at its higher elevation.

Tacoma Power owns Riffe Lake's shoreline, most of which is designated for wildlife habitat.

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