Hydrology of Park County, Wyoming, Exclusive of Yellowstone National Park

Lowry, Marlin; Smalley, Myron; Others

Unconsolidated deposits are a principal source of ground water in Park County. However, the presence of water in deposits topographically higher than stream level depends on recharge from surface water used for irrigation. Terraces that are not irrigated, such as Polecat Bench, do not have saturated deposits from which water can be obtained. Water in the unconsolidated deposits, although dependent upon infiltration of applied surface water, is of poorer quality than the applied surface water because of solution of salts as the water moves through the soil. The conversion of irrigated agricultural land to urban development poses problems in some areas because yields of water-supply wells will be adversely affected by reduced recharge. Water in unconsolidated deposits is at shallow depths, thus, the trend toward urban development increases the risk of contamination from septic tanks, petroleum products, and accidental spills of toxic and hazardous wastes. Ground water suitable for domestic use is difficult to obtain in some areas where it is needed because of poor yields and poor quality in shallow aquifers. Large areas suitable for urban development are underlain by thick shales that have low well yields and poor water quality. Folding of rocks during the mountain-forming process in western Wyoming has resulted in some of the aquifers being too deeply buried to be considered as a source of water for either domestic or stock supplies. Although many of these aquifers may contain water of good quality near the surface, the quality usually becomes poorer with depth and is not suitable for domestic use. Ground water is present throughout most of the county and most ground-water flow stays within the county. A small, unquantified amount of water flows through the county in the aquifers. The aquifers are continuous from the edges of the mountains into the badlands and plains and beyond county boundaries. The climate of Park County varies from alpine tundra to desert. Altitudes range from 12,000 feet above sea level in the mountains to 4,015 feet where the Clarks Fork Yellowstone River flows into Montana. Annual precipitation averages up to 40 inches in the mountains, but only 6 inches near the eastern edge of the county. Perennial streams in the county originate in the mountains; streams originating in badlands and plains are ephemeral unless they drain an area irrigated by surface water so that return flow is sustained during the winter. The average annual runoff of streams that originate in the mountains is as large as 598 acre-feet per square mile; for streams that originate in the badlands and plains, annual runoff is as low as 14.8 acre-feet per square mile.

Hydrology of Park County, Wyoming, Exclusive of Yellowstone National Park

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