Ground Water of the Northern High Plains

Geology

Ground water found Northern High Plains is largely supplied by the Ogallala Formation. The Ogallala Formation ranges from a few feet in thickness at its westernmost border to up to 400 feet in thickness north of Wray. The thickness of the aquifer depends on the shape of the underlying bedrock.

The Ogallala Formation is comprised of cemented and uncemented clays, silts, sands, and gravels which overlie shale and siltstone. Dune sand and alluvium, ranging in thickness from a few inches to over 100 feet, overlie the Ogallala Formation.

The water in Ogallala Formation moves eastward toward Nebraska and Kansas.

The Ogallala Formation contains an estimated 80 million acre-feet of recoverable ground water.

Well Yields and Ground Water Quality in the Northern High Plains

Well yields range from several gallons per minute up to 2000 gallons per minute. Well yields of at least 500 gallons per minute are necessary for irrigation. These well yields are found only in areas where the saturated thickness of the aquifer is greater than 50 feet.

Water quality is best in the northern regions which are overlain by sand. Water quality diminishes to the west and to the south where the aquifer is thinner and underlain by shale. In general, concentrations of dissolved solids range from 100 to 500 milligrams per liter.

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