Moses Coulee till, up to thick in places. This glacial till, made up of clay, silt, sand, gravel, cobblestones, and erratic boulders, covers most of the upper coulee. Today Moses Coulee supports an excellent example of a shrub-steppe ecoregion. Vegetation includes sagebrush, rabbitbrush, greasewood, hopsage, bitterbrush, bunchgrass, buckwheat and other vegetation once common to most of the Columbia Plateau. The Nature Conservancy has established the Moses Coulee Preserve, which is a contiguous, intact shrub-steppe habitat. It is located south of Jameson Lake near the head of Moses Coulee. It provide habitat for a rich variety of birds (lazuli bunting, common goldeneye, sage
Grand Coulee Dam interest in irrigation projects. The Bureau of Reclamation, desirous of a major project that would bolster its reputation, was focusing on the Boulder Canyon Project that resulted in the Hoover Dam. Reclamation was authorized to conduct a study in 1923, but the project's cost made federal officials reluctant. The Washington state proposals received little support from those further east, who feared the irrigation would result in more crops, depressing prices. With President Coolidge opposed to the project, bills to appropriate money for surveys of the Grand Coulee site failed. In 1925, Congress authorized a U.S. Army Corps of Engineers study