Grays Lake lies within the Caribou Range of the Rocky Mountains in southeast Idaho, and is at the western edge of the Greater Yellowstone Ecosystem. The valley lies about 30 miles north of Soda Springs, Idaho and about 70 miles southwest of Jackson Hole, Wyoming. At the heart of the valley is a large, shallow montane marsh, composed primarily of hardstem bulrush and cattail with scattered small ponds. This wetland system provides important habitat for breeding sandhill cranes, trumpeter swans, Franklin's gulls, white-faced ibis, dabbling and diving ducks, a variety of shore- and grassland birds, as well as habitat for molting and fall-staging waterfowl and cranes. The area is significant for its high density of breeding sandhill cranes and as a reintroduction site for trumpeter swans. The richwet meadow edges of the marsh provide foraging and nesting habitat for a diversity of water birds each year. Grays Lake National Wildlife Refuge encompasses much of the richest wetland habitat within the valley. It was established in 1965 to protect and restore habitat for waterfowl production, sandhill cranes, and other wildlife. In the 1970s and 1980s the refuge served as the focus of an effort to establish a second wild population of endangered whooping cranes. Currently, the refuge's goals are to enhance natural ecosystem functions to support a diversity of water birds and other wildlife.
Average annual snowfall ; average accumulations of 40-50 inches.
Daytime high temperatures average 68-75 °F in June and July.
Hard frosts may occur in any month.
Record high of 103 °F recorded in 1919 and record low of –62 °F on January 1, 1978.
Habitat and plant communities
Transitional zone between Great Basin vegetation and Rocky Mountain vegetation.
Within approved refuge boundary, 60% palustrine emergent wetland, 20% wetland semi-wet meadow, 12% brush, grasslands, and grain fields, 5% shallow open water with submergents, and 3% aspen forest and willow thicket.
Over 170 species of grasses, sedges and forbs in wet meadows and marsh habitat, including 15 species of sedges.
3 species of exotic, invasive plants.
7 species of trees and 17 species of shrubs
No known threatened or endangered plant species.
Wildlife
128 recorded species of breeding birds present.
Over 40 bird species nesting in the wet meadow and wetland habitats of the basin.
20 species of mammals.
4 species of amphibians.
6 species of reptiles.
1 species protected as "threatened or endangered".
Highest breeding density of sandhill cranes in North America - an important breeding area for Rocky Mountain Population of sandhill cranes.
700-800 cranes present in May; 1,000 or more cranes stage in the basin in September.
Nesting colonies of Franklin's gulls and white-faced ibis.
Water
Located within Willow Watershed, 651.45 mi2 in size.
Average water depth 11.5 feet in spring; <0.5 ft in late July through September.
Water sources from snowmelt and numerous springs; main inflow via Willow, Eagle, and Gravel Creeks on the east and south, and Crane Creek on the west.
Original water outlet, Grays Lake Outlet, drains to the north into Snake River via Willow Creek.
Clark's Cut, a man-made channel completed in 1924, drains into the Blackfoot Reservoir via Meadow creek.
