SOIL SURVEY OF WHITMAN COUNTY, WASHINGTON

WHITMAN COUNTY is in the southeastern part of Washington (fig. 1). It has an area of 1,385,370 acres. Most of the county has a rolling to hilly topography and deep soils that formed in silty material deposited by wind. Basalt is the base rock, but there are a few promontories of quartzite, shale, and sandstone. Elevation is about 4,000 feet in Tekoa Mountain, the highest part of the county. Channeled scablands (3) in the western part of the county consist of a broad basalt plateau that was stripped of soil by glacial floodwaters. Many islandlike remnants of preglacial soils remained after the glacial floods. Channels that run in a southwest direction were cut in the basalt bedrock. Some are now occupied by potholes and lakes. Bonnie and Rock Lakes are in this area. Most of the survey area drains into the Palouse River and its tributaries. The Palouse River heads in the mountains of Idaho adjacent to the eastern boundary of the county, and the north and south forks of the river converge near the center of the county at Colfax. It flows west and south from Colfax to its junction with the Snake River at the extreme southwest corner of the survey area. Principal tributaries of the Palouse River include Rock, Pine, and Cottonwood Creeks in the northern and northwestern parts of the survey area and Union Flat, Rebel Flat, and Willow Creeks in the southern and southwestern parts. The southern part of the survey area consists of a narrow band of very steep soils along the Snake River Canyon that drain directly into the Snake River. Hangman Creek, a perennial tributary to the Spokane River, drains an area of about 20 square miles in the northeastern part of the county. Its drainage water ultimately flows into the Columbia River. Wheat is the major cultivated crop. Barley, peas, lentils, grass, and alfalfa are other important crops. Soils on the breaks of the Snake River, on the channeled scablands, and on the buttes are used mostly for range and wildlife habitat.