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STATE OF UTAH DEPARTMENT OF NATURAL RESOURCES Technical Publication No. 113 HYDROLOGY OF SANPETE VALLEY, SANPETE AND JUAB COUNTIES, UTAH, AND SIMULATION OF GROUND-WATER FLOW IN THE VALLEY-FILL AQUIFER By D.E. Wilberg and V.M. Heilweil U.S. Geological Survey Prepared by the United States Geological Survey, in cooperation with the Utah Department of Natural Resources, Division of Water Rights 1995 CONTENTS Abstract 1 Introduction 1 Purpose and scope................................................................................................................................. 1 Methods of investigation 3 Numbering system for hydrologic-data sites in Utah 3 Acknowledgments 3 Description of the study area................................................................................................................. 5 Geology 5 Climate 7 Vegetation '" 8 Surface-water hydrology.................................................................................................................................. 8 San Pitch River...................................................................................................................................... 9 Tributary inflow.................................................. 9 Transbasin diversions and storage facilities 11 Water quality............................................................ 11 Ground-water hydrology 13 Consolidated rock 13 Valley-fill aquifer 14 Recharge 14 Seepage from tributaries and the San Pitch River 14 Infiltration of unconsumed irrigation water...................................................................... 16 Infiltration of precipitation................................................................................................ 16 Movement......................................................................................................................... 16 Discharge...................................................................................................................... 18 Evapotranspiration 18 Seepage to the San Pitch River 19 Withdrawals from wells 19 Alluvial-spring discharge 21 Hydrologic properties '" '" '" 21 Water-level fluctuations 22 Water quality 23 Simulation of the ground-water flow system in the valley-fill aquifer 29 Modeling approach 29 Discretization 30 Boundary conditions................................................................................................................... 30 No-flow boundaries........................................................................................................... 30 Head-dependent flux boundaries 30 Constant-flux boundaries 30 Distribution of hydrologic properties 35 Steady-state calibration .. 35 Recharge.. 35 Discharge..................................................................................................................................... 38 Hydrologic properties 41 Horizontal hydraulic conductivity and transmissivity................... 41 Vertical hydraulic conductivity and leakance 41 Comparison of measured and model-computed water levels...................................................... 45 Transient-state calibration 45 Recharge 52 iii CONTENTS-Continued Discharge..................................................................................................................................... 52 Hydrologic properties.................................................................................................................. 52 Comparison of measured and model-computed water-level changes 54 Sensitivity analysis 59 Limitations of the model 60 Simulation of increased ground-water withdrawals 61 Summary 65 References cited............................................................................................................................................... 68 PLATE [Plate is in pocket] 1. Map showing location of data-collection sites, Sanpete Valley, Utah FIGURES 1. Map showing location ofSanpete Valley study area, Utah................................................................ 2 2. Diagram showing numbering system for hydrologic-data sites in Utah............................................ 4 3. Graph showing relation of natural logarithm of average annual streamflow to five tributary drainage-basin areas, Sanpete Valley, Utah :.................. 10 4. Diagram showing percentage of predominant dissolved ions in water from five surface-water sites in Sanpete Valley, Utah. 12 5. Map showing potentiometric contours of water levels measured in the valley-fill aquifer, Sanpete Valley, Utah, November 1989 17 6-8. Graphs showing: 6. Annual ground-water withdrawals from pumped wells in Sanpete Valley and average annual precipitation at Meadows climatic station, Utah, calendar years 1963-89.................................. 20 7. Short-term water-level fluctuations in four wells in Sanpete Valley, Utah, 1987-90 24 8. Relation of long-term water-level fluctuations in three wells in Sanpete Valley to cumulative departure from average annual precipitation at Meadows climatic station, Utah, 1935-90........ 25 9. Diagram showing percentage of predominant dissolved ions in water from four wells and two springs in consolidated-rock aquifers, Sanpete Valley, Utah... 26 10. Diagram showing percentage of predominant dissolved ions in water from 15 wells and I spring in the valley-fill aquifer, Sanpete Valley, Utah...... 28 11-21. Maps showing: I I. Location of the ground-water flow model in relation to the study area and valley-fill boundaries, Sanpete Valley, Utah 3I 12. Location of active, inactive, ri ver, and head-dependent boundary cells in layer 1 of the ground-water flow model ofSanpete Valley, Utah 32 13. Location of active and inactive cells and cells that simulate discharge from pumped and flowing wells in layer 2 of the ground-water flow model of Sanpete Valley, Utah 33 14. Location of active and inactive cells and cells that simulate discharge from pumped wells in layer 3 of the ground-water flow model ofSanpete Valley, Utah...... 34 15. Location of cells that simulate recharge from infiltration of precipitation and unconsumed irrigation water and seepage from tributaries in layer I of the ground-water flow model of Sanpete Valley, Utah 37 16. Location of evapotranspiration cells and cells simulating alluvial-spring discharge in layer I of the ground-water flow model of Sanpete Valley, Utah............................................................ 39 iv FIGURES-Continued 11-21. Maps showing:-Continued 17. Final distribution of hydraulic-conductivity values used for layer 1 of the ground-water flow model of Sanpete Valley, Utah 42 18. Final distribution of transmissivity values used for layer 2 of the ground-water flow model of Sanpete Valley, Utah 43 19. Final distribution oftransmissivity values used for layer 3 of the ground-water flow model of Sanpete Valley, Utah.................................................................................................................... 44 20. Potentiometric contours of measured and model-computed steady-state water levels for the valley-fill aquifer, Sanpete Valley, Utah 51 21. Final distribution of specific-yield values used for layer 1 of the ground-water flow model of Sanpete Valley, Utah.................................................................................................................... 53 22. Hydrographs showing measured and model-computed water-level changes in selected wells in Sanpete Valley, Utah, for the 1968-89 transient-state calibration 55 23. Map showing model-computed water-level decline in layer 2 resulting from simulated pumping at triple the average 1963-88 rates for 20 years, Sanpete Valley, Utah........ 63 24. Map showing model-computed water-level decline in layer 2 resulting from simulated pumping at triple the average 1963-88 rates for a 5-year drought with 75 percent of simulated steady-state recharge, Sanpete Valley, Utah.................... 64 TABLES 1. Selected data for seven climatic stations in the Sanpete Valley study area, Utah.............................. 7 2. Measured or estimated components of the ground-water budget for the valley-fill aquifer in Sanpete Valley, Utah 15 3. Measured or estimated and model-computed components of the ground-water budget for the valley-fill aquifer in Sanpete Valley, Utah 36 4. Measured and model-computed water-level altitudes in selected wells, Sanpete Valley, Utah......... 46 5. Model-computed components of the ground-water budget for steady-state calibration and predictive simulations in the valley-fill aquifer in Sanpete Valley, Utah 65 6. Discharge, specific conductance, and temperature of water from selected surface-water sites and springs, Sanpete Valley, Utah...................... 70 7. Results ofchemical analyses of water from five selected surface-water sites, Sanpete Valley, Utah 74 8. Records of selected wells, Sanpete Valley, Utah................................................................................ 76 9. Water levels in selected wells, Sanpete Valley, Utah 82 10. Discharge, specific conductance, and temperature of water from selected flowing and pumped wells, Sanpete Valley, Utah. 109 11. Results ofchemical analyses of water from selected wells and springs, Sanpete Valley, Utah......... 120 v CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATED WATER-QUALITY UNITS Multiply By To obtain acre 0.4047 hectare 4,047 square meter acre-foot (acre-ft) 0.001233 cubic hectometer 1,233 cubic meter acre-foot per year (acre-ft/yr) 0.00003907 cubic meter per second cubic foot per second