MOUNTAIN BLOCK AQUIFERS SURROUNDING CEDAR CITY, UTAH

Precipitation that infiltrates each year into bedrock aquifers east and west of Cedar City, within the Cedar Valley drainage basin, provides a substantial ground water resource that is not being developed. The minimum published estimate for infiltration is equal to five (5) percent of the annual precipitation, while recent publications discussing infiltration in the southwestern U.S. have demonstrated that infiltration into mountain block aquifers is more likely to equal or exceed ten (10) percent.

Records from the Desert Research Institute in Las Vegas, Nevada, show that extremes of annual precipitation through 2006 at the Cedar City Airport ranged from 5.2 inches in 1959 to 16.94 inches in 1967. However, mountain block precipitation 3,500 feet higher at the Webster Flat SNOTEL weather station ranged from 14.4 inches in 2002 to 50.6 inches in 2005.

Annual recharge into the bedrock aquifers east of Cedar City within the Cedar Valley drainage basin ranges from at least 9,500 to more than 19,000 acre-feet. Annual recharge into the bedrock aquifers west of Cedar City ranges from at least 2,200 to more than 4,400 acre-feet. Most of that ground water flows away from the Cedar Valley drainage basin in the subsurface without being utilized by the citizens of Cedar City and Iron County.

The ability to average out annual water availability is an important advantage of bedrock aquifers: infiltrating ground water provides an average amount of storage over many centuries of time. For example, if (1) the average annual recharge into the bedrock flanking Coal Creek east of Cedar City is about 10,000 acre-feet; and (2) water stored in potential aquifers is about 40,000,000 acre-feet, then all of the water in connected pore spaces would be replaced in about 4,000 years. Displaced water flows out of springs, or moves laterally and vertically in the subsurface, out of the drainage basin.