Grassy Lake

Quick Facts

Grassy Lake

Idaho

(208) 624-3151

Map Directions

Things To Do

Overview

Grassy Lake which is formed by Grassy Lake Dam is a major feature on the Mindoka Project. This 1,477-acre reservoir is located near the Wyoming-Idaho border between Yellowstone and Grand Teton National Parks. Fish species include rainbow, cutthroat, and lake trout. Reservoir acre feet and total reservoir capacity and cubic feet/second release rates for rivers below Upper Snake River Basin reservoirs and select river locations are updated daily and graphically provided. No improvements, services, or facilities.

Grassy Lake Dam is a 118-foot-high zoned earthfill storage dam on Grassy Creek in Wyoming near the southern boundary of Yellowstone National Park. The reservoir has a total storage capacity of 15,500 acre-feet (active 15,200 acre-feet) which supplements the storage at Island Park. Storage at Grassy Lake Dam is augmented by a 0.7-mile canal from Cascade Creek which is fed from the Cascade Creek Diversion Dam, a rockfilled log crib weir that is 14 feet high.

Recent operation and maintenance modifications included the installation of a seepage blanket and drain at the toe of the dam in 1996 and 1997. Due to the poor condition of the spillway chute concrete, the reservoir has been restricted 1 foot below full capacity for the summer resulting in a storage capacity of 14,800 acre-feet. During the winter, there is a 5-foot restriction resulting in a storage capacity of 13,655 acre-feet. Corrective action work is expected to be completed in the year 2000 at which time the operating restrictions will be rescinded. Because of these restrictions, no spillway releases are allowed.

Map of Grassy Lake

Latitude, Longitude: 42.218394, -113.534762

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Activities

  • Boating

    No improvements, services, or facilities.

  • Fishing

    Fish species include rainbow, cutthroat, and lake trout. Reservoir acre feet and total reservoir capacity and cubic feet/s.

  • Hunting

    Hunting allowed in designated areas.

  • Water Sports

    Swimming, fishing and boating.

Directions

Driving

Fair access via Forest Service Road 135, east of U.S. 89/287.

Phone Numbers

Primary

(208) 624-3151

Links