EFFECTS OF GROUND-WATER RECHARGE AND PUMPING AS DETERMINED FROM GROUND-WATER LEVEL ANALYSIS IN CEDAR VALLEY, UTAH COUNTY, UTAH

The Utah Geological Survey is constructing a ground-water flow model to provide a tool for the sound management of the ground-water resources of Cedar Valley, Utah County, in north-central Utah. Analysis of new and existing ground-water level and pumping data for this study reveals important information about the hydraulic connections and recharge patterns in the Cedar Valley ground-water system.

Ground-water levels in the basin-fill aquifer from year to year are affected by the volume of recharge entering the aquifer at its western margin. The effect of recharge from the west may take up to nine years to be observed in wells distant from the recharge source. Increased ground-water pumping in the past decade has had little negative effect on most of the aquifer, but may be lowering water levels near the eastern margin of the valley where pumping has increased.

Fairfield Spring, the largest spring in the valley and an important source of water for residents, issues from basin-fill sediments on the central-western margin of the valley. I show spring discharge to be controlled by the potentiometric head in the underlying confined aquifer, proving that a long-suspected hydraulic connection between the spring and the aquifer does exist. The head in the aquifer, in turn, is controlled primarily by the volume of recharge to the aquifer from precipitation infiltration. Pumping from the confined aquifer 2 miles from the spring and roughly perpendicular to ground-water flow direction has no discernable effect on spring discharge unless below normal recharge years (drought) are coincident with very heavy pumping, as has historically occurred only in the 1960s.