The U.S. Geological Survey formally started a program for monitoring ground-water quality in Utah during 1957 in cooperation with the State of Utah. Most observation wells in the monitoring network are privately owned. Initially, the network consisted of fewer than 50 wells; by 1984, however, it had expanded to include more than 200 wells. Chemical analyses are available for water from some of the wells from as early as 1927, long before those wells were formally added to the network. The monitoring program was initiated to detect any changes in chemical quality that might be associated with the withdrawal of water from wells.
Dissolved-solids concentrations in water samples collected from the observation wells through 1984 ranged from 92 to 19,000 milligrams per liter. An observation well in the Uinta Basin yielded the sample with the smallest dissolved-solids concentration, and another well in the Uinta Basin yielded the sample with the largest dissolved-solids concentration. There was a progressive increase in salinity of water produced by several of the observation wells in Pahvant Valley and in the Milford and Beryl-Enterprise areas. The increases in salinity occurred during 1950-84, coinciding with the decline of water levels due to pumping for irrigation. Water-quality changes related either to ground-water withdrawals or ground-water recharge also were detected in several other areas, including Curlew Valley, Cedar City Valley, Northern Utah Valley, the lower Bear River valley, and the Sevier Desert.
Water produced from wells in Goshen Valley and the upper Fremont River valley had short term increases in chloride, sulfate, and dissolved-solids concentrations, indicating possible local contamination of the ground water. Also, since the late 1950's, dissolved-solids concentrations have increased in water produced by a well completed in the principal aquifer in Salt Lake Valley downgradient from areas where extensive use has been made of road salt.
