The impounded water behind the dam forms Alder Lake, stretching about 7 miles (11 km) upstream with a capacity of 241,950 acre-feet (0.29844 km3).

With 28 miles (45 km) of shoreline, the lake is a popular recreation spot close to Mount Rainier National Park.

Most of the energy produced at the dam is sent to the city of Tacoma, about 25 miles (40 km) north.

[4] Both Alder and LaGrande dams are owned and operated by Tacoma Power.

[5] The current community of Alder is located north of the reservoir.