Abstract

Beaver and Cedar Valleys, in southwestern Utah, are experiencing an increase in residential development that relies on basin-fill aquifers as the primary source of drinking water. In response to local governments’ desire to protect these high quality resources, we provide ground-water quality classification maps as land-use planning tools.

Ground-water quality classification is a means for local governments in Utah to manage potential ground-water contamination sources and protect the quality of their ground-water resources. Classifying the ground-water quality of the principal aquifers formally identifies and documents the beneficial use of ground-water resources allowing defendable land-use regulations to be enacted. Utah’s ground-water quality classes are based mostly on total-dissolved-solids concentrations as follows: Class IA (Pristine), less than 500 mg/L; Class II (Drinking Water Quality), 500 to less than 3000 mg/L; Class III (Limited Use), 3000 to less than 10,000 mg/L; and Class IV (Saline), 10,000 mg/L and greater.

In Beaver Valley, we classify the ground water in 85% of the aquifer as Class IA ground water (primarily at the basin margins and northern parts of the valley) and 15% of the aquifer as Class II ground water (in the western- and southernmost parts of the valley) based on chemical analyses of water from 50 wells sampled during September 2005 and March 2007. Total-dissolved-solids concentrations range from 92 to 1280 mg/L. In Cedar Valley, we classify ground water in 80% of the aquifer as Class IA (primarily in central and western parts of valley), 19% Class II (primarily in eastern part of valley), and the remainder 1% as Class III (an area of persistent nitrate high concentration northwest of Cedar City) based on chemical analyses of water from 97 wells sampled during 1974-2000. Total-dissolved-solids concentrations range from 184 to 2190 mg/L. The ground-water quality classification maps presented here provide land-use planners in both valleys a basis for enacting regulations to protect water resources in these growing rural communities.