STATE OF UTAH DEPARTMENT OF NATURAL RESOURCES Technical Publication No. 114 HYDROLOGY AND SIMULATION OF GROUND-WATER FLOW IN JUAB VALLEY, JUAB COUNTY, UTAH By Susan A. Thiros, Bernard J. Stolp, Heidi K. Hadley, and Judy I. Steiger U.S. Geological Survey Prepared by the United States Geological Survey in cooperation with the Central Utah Water Conservancy District and the East Juab Water Conservancy District 1996 CONTENTS Abstract 1 Introduction I Purpose and scope....................... 4 Previous studies 4 Acknowledgments 4 Description of the study area 4 Geology 5 Climate g Hydrology......................................................................................................................................................... 11 Surface water 11 Streams 11 Distribution systems 16 Reservoirs......................... 18 Ground water 19 Occurrence.............................................................. 19 Recharge................................ 20 Seepage from streams...................... 20 Seepage from unconsumed irrigation water and distribution systems 20 Infiltration of precipitation 24 Subsurface inflow 24 Flow............................................................................................................................................. 25 Discharge..................................................................................................................................... 25 Wells 25 Springs and seeps.............................................................................................................. 2g Evapotranspiration 30 Subsurface outflow......... 30 Hydrologic properties.................................................................................................................. 30 Water-level fluctuations............................................................................................................... 34 Long-term fluctuations...................................................................................................... 34 Seasonal fluctuations........... 34 Chemical characteristics of water............ 41 Chemical composition 41 Isotopes........................................................................................................................................ 4g Geochemical analyses 50 Simulation of the ground-water system in the unconsolidated basin-fill deposits of Juab Valley................... 53 Model construction..................... 54 Discretization 54 Boundary conditions and data requirements 56 Recharge 57 Discharge.......................................................................................................................... 65 Hydrologic properties 72 Model calibration 73 Calibration parameters 73 Steady-state calibration g2 Transient-state calibration g5 Model sensitivity 93 Model limitations 96 iii CONTENTS-Continued Need for future study........................................................................................................................................ 97 Summary 98 References cited. 99 PLATE IPlate is in pocketI Plate 1. Map showing location of selected hydrologic-data sites and rock-sample site, Juab Valley, Utah, 1935-94 FIGURES 1. Map showing location of Juab Valley study area, Utah 2 2. Diagram showing numbering system used in Utah for hydrologic-data sites 3 3. Map showing generalized geology of the Juab Valley study area, Utah............................................ 6 4. Generalized cross section through the southern part of Juab Valley, Utah 9 5. Graphs showing annual precipitation and cumulative departure from the average annual precipitation, 1931-93, at Nephi, Utah............................................................................................... 10 6. Map showing discharge-measurement sites on Salt Creek, on selected irrigation canals and ditches, and in the West Creek area, Juab Valley, Utah 14 7. Graphs showing estimated average seepage gain or loss for reaches of Salt Creek and selected irrigation canals and ditches, Juab Valley, Utah................................................................................. 17 8. Map showing approximate potentiometric surface in unconsolidated basin-fill deposits in Juab Valley, Utah, March and April 1993 26 9. Map showing areal distribution of transmissivity estimated from specific-capacity values, slug tests, and aquifer tests for unconsolidated basin-fill deposits in Juab Valley, Utah 32 10. Hydrographs showing March or April water levels measured during 1942-94 in four wells in Juab Valley, Utah, and cumulative departure of the annual maximum water content of snow from the 1942-94 average at the Payson Ranger Station snow course 35 11. Hydrographs showing long-term water-level fluctuations during 1935-94 in eight wells in Juab Valley, Utah 36 12. Map showing approximate change in water levels in unconsolidated basin-fill deposits from March-April 1965 to March-April 1993 in Juab Valley, Utah 38 13. Hydrographs showing seasonal water-level fluctuations during 1993-94 in four wells in Juab Valley, Utah 40 14. Hydrographs showing seasonal water-level fluctuations during 1937-38, 1965-66, and (or) 1993-94 in four wells in Juab Valley, Utah........................................................................................ 42 15. Map showing dissolved-solids concentration in water from the Juab Valley study area, Utah, 1951-94 44 16. Graphs showing relation between specific conductance of water and streamflow at gaging stations on Salt Creek, Chicken Creek, and Currant Creek, Juab Valley, Utah 47 17. Graph showing relation between 0180 and oD values for water sampled from selected hydrologic-data sites in Juab Valley, Utah 49 18. Graph showing relation between log calcium and log sulfate activity for water sampled along the hypothesized Chicken Creek drainage flow path in Juab Valley, Utah 52 19. Map showing model grid and location of active cells in the ground-water flow model of Juab Valley, Utah ,.................................................... 55 20. Generalized geology and the four layers used in the ground-water flow model of Juab Valley, Utah 56 iv FIGURES-Continued 21. Graph showing depth from the estimated top of the saturated unconsolidated basin-fill deposits, the amount of 1963-93 average annual ground-water discharge to pumped wells in each depth interval, and corresponding model layers in the ground-water flow model of Juab Valley, Utah ..... 57 22-29. Maps showing: 22. Location of specified-flux boundary cells that simulate recharge from nonirrigation-season streamflow, unconsumed irrigation water and distribution-system losses, and irrigation­ season streamflow not included in the unconsumed irrigation water and distribution-system losses component in the ground-water flow model of Juab Valley, Utah.................................... 59 23. Location of specified-flux boundary cells that simulate recharge from subsurface inflow and seepage from ephemeral streams and discharge by subsurface outflow in the ground-water flow model of Juab Valley, Utah.................................................................................................. 66 24. Location of specified-flux boundary cells that simulate discharge to pumped wells in the ground-water flow model of Juab Valley, Utah 67 25. Location of head-dependent flux boundary cells that simulate discharge to flowing wells, springs, seeps, streams, and reservoirs in the ground-water flow model of Juab Valley, Utah... 69 26. Location of head-dependent flux boundary cells that simulate discharge by evapotranspiration in the ground-water flow model of Juab Valley, Utah 71 27. Final distribution of horizontal hydraulic conductivity for layers I through 3 of the ground- water flow model of Juab Valley, Utah........................................................................................ 76 28. Final distribution of transmissivity for layer 4 of the ground-water flow model of Juab Valley, Utah 78 29. Final distribution of vertical hydraulic conductivity for layers I through 4 of the ground- water flow model of Juab Valley, Utah........................................................................................ 81 30. Hydrographs showing water level in selected wells in Juab Valley, Utah 83 31. Map showing potentiometric surface for model layer 3 contoured from water levels computed from the steady-state simulation for 1949 and the difference between model-computed and measured water levels in observation wells, Juab Valley, Utah, March 1950................................... 84 32. Graph showing estimated annual ground-water discharge to pumped wells, length of stress periods, and average annual pumpage for each stress period of the multi-year transient-state simulation, Juab Valley, Utah............................................................................................................. 86 33. Hydrographs showing model-computed and measured water-level change in selected wells in Juab Valley, Utah, for the multi-year transient-state simulation 88 34. Map showing potentiometric surface for model layer 3 contoured from water levels computed from the transient-state simulation for 1964 and the difference between model-computed and measured water levels in observation wells, Juab Valley, Utah, March 1965................................... 90 35. Map showing potentiometric surface for model layer 3 contoured from water levels computed from the transient-state simulation for 1992 and the difference between model-computed and measured