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Grays Lake Ecosystem

Gray's Lake, Bonneville & Caribou Counties, Idaho

Notes from a survey conducted June 10, 1929
by Charles C. Sperry and A. C. Martin, U.S. Biological Survey

Shores: Sedge and grass meadows varying in width from a few rods to a half mile or more. Hay is cut from some of these bottoms but their chief use is as grazing land for stock especially sheep.

Bottom: Compact tule or sedge sod except in the open ponds where the firm mud bottom is covered with from 12 to 18 inches of black ooze.

Inlets: Springs and local drainage from the nearby mountains. Principal inlets are Willow Creek and Bridge Creek on the east and Gravel Creek on the south.

Outlets: Gray's Lake Outlet (or Bear Creek) leads from the northwest corner of the lake and is the only natural outlet. However, this natural outlet is now controlled by gates while a ditch (opened in 1924-25) at the southwest corner conducts surplus water into Meadow Creek and finally into the Blackfoot River Reservoir through Pelican Slough. Thus Gray's Lake becomes an auxiliary to the Blackfoot River Reservoir.

Water: The water is clear with a pH value of 7.3 to 7.6 and varies in depth from a few inches (marsh) to 3 feet in the open ponds.



Submerged vegetation is of minor importance except in the 500-ac patch of open water at the south end. There, however, a fine stand of leafy pondweed, Myriophyllum, and coontail as well as floating and submerged duckweeds provides an abundance of succulent green foods to complement the vast quantities of grain produced in the marsh.


Gray's Lake is not a lake at all but a great marsh, covered with from few inches to 2-3 feet of water, in the center of which rises the mountain, Bear Island ¼ to ½ mile wide and 1½ miles long. At the south end of the lake a 500-ac expanse of water is dotted with little marsh islands. While small ponds and open channels are frequent long either shore. The interior of the lake is a broad and almost unbroken expanse of the big bulrush.

Wildfowl: Gray's Lake no doubt is frequented by all species of marsh birds that nest or migrate through the Rocky Mountain region of the United States. Mallards and teals are reported to nest in abundance in the marsh. In addition to broods of these ducks, other species seen during this survey were: gadwall, widgeon, pintail, mud hen, American bittern, jacksnipe, black tern, and yellow-headed blackbird. Gray's Lake produces an enormous surplus of wild duck foods.

Muskrats: Gray's Lake is a fine muskrat territory and probably the only serious opposition to making it a bird refuge will come from those people who have been accustomed to reap the annual fur harvest.

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