GROUND-WATER FLOW IN THE DUCHESNE RIVER-UINTA AQUIFER, UINTA BASIN, UTAH AND COLORADO By Kent C. Glover U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 92-4161 Cheyenne, Wyoming 1996 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Gordon P. Eaton, Director The use of trade, product, industry, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. For additional information Copies of this report can be write to: purchased from: District Chief U.S. Geological Survey U.S. Geological Survey, WRD Branch of Information Services 2617 E. Lincolnway, Suite B Box 25286, Denver Federal Center Cheyenne, Wyoming 82001-5662 Denver, Colorado 80225 CONTENTS Abstract ................................................................................................................................................................................ 1 Introduction...............................................................................................^^ 1 Duchesne River-Uinta aquifer and associated geohydrologic units ..................................................................................... 3 Distribution of hydraulic head in the Duchesne River-Uinta aquifer .................................................................................. 4 Recharge and discharge in the Duchesne River-Uinta aquifer............................................................................................. 9 Aquifer properties ................................................................................................................................................................ 12 Analysis of steady-state flow in the Duchesne River-Uinta aquifer .................................................................................... 13 Development of flow model...................................................................................................................................... 13 Initial estimates of hydraulic characteristics.................................................................................................. 15 Calibration................................................................................................................................................^ 15 Results of flow simulation ........................................................................................................................................ 16 Recharge........................................................................................................................................................ 16 Discharge..........................................................................................................~^ 18 Transmissivity ............................................................................................................................................... 18 Comparison of simulation results with measured water-level data........................................................................... 20 Summary .............................................................................................................................................................................. 23 Selected references................................................................................................................................................................ 23 FIGURES 1. Map showing location of the Uinta Basin............................................................................................................... 2 2. Stratigraphic relation between early Oligocene and Eocene geologic units and geohydrologic units................... 4 3-5. Maps showing: 3. Altitude and configuration of the base of the Uinta Formation..................................................................... 5 4. Surficial geology of the Uinta Basin and adjacent areas................................................................................ 6 5. Potentiometric surface (1985) of the Duchesne River-Uinta aquifer............................................................ 7 6. Graph showing variograms of hydraulic head in the Duchesne River-Uinta aquifer............................................. 8 7. Map showing initial distribution of estimated ground-water recharge................................................................... 11 8. Graph showing variogram of hydraulic conductivity for the Duchesne River-Uinta aquifer................................. 13 9-13. Maps showing: 9. Finite-difference grid used to model ground-water flow in the Duchesne River-Uinta aquifer.................... 14 10. Model-calibrated recharge for the Duchesne River-Uinta aquifer................................................................. 17 11. Basin distribution of transmissivity for the Duchesne River-Uinta aquifer .................................................. 19 12. Simulated hydraulic-head contours for the Duchesne River-Uinta aquifer................................................... 21 13. Residuals for the Duchesne River-Uinta aquifer model................................................................................ 22 TABLES 1. Ground-water discharge from the Duchesne River-Uinta aquifer to streams in the Uinta Basin estimated from streamflow data......................................................................................................................................... 10 2. Ground-water recharge and discharge along the Green and Uinta Rivers estimated during model development....................................................................................................................................................... 18 CONTENTS III CONVERSION FACTORS AND VERTICAL DATUM Multiply By To obtain inch (in.) 25.4 millimeter foot (ft) 0.3048 meter mile (mi) 1.609 kilometer square mile (mi2) 2.590 square kilometer cubic foot per second (ft3/s) 0.02832 cubic meter per second Sea level: In this report "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)--a geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929. IV GROUND-WATER FLOW IN THE DUCHESNE RIVER-UINTA AQUIFER, UINTA BASIN, UTAH AND COLORADO GROUND-WATER FLOW IN THE DUCHESNE RIVER-UINTA AQUIFER, UINTA BASIN, UTAH AND COLORADO By Kent C. Glover ABSTRACT Large areas of the Duchesne River-Uinta aquifer are characterized by a transmissivity of about The Duchesne River and Uinta Formations 4,400 feet squared per day. In the center of the form the Duchesne River-Uinta aquifer, an impor­ model area, an aquifer test indicated a value of tant basin aquifer that is about 8,000 feet thick in 900 feet squared per day where the model yielded the north-central part of the Uinta Basin in Utah a value of 4,400 feet squared per day with an esti­ and Colorado. Ground-water recharge within the mated standard error of 1,500 feet squared per day. Duchesne River-Uinta aquifer is derived from pre­ Transmissivity within the Duchesne fault zone in cipitation and from seepage losses from canals and the western part of the study area and along the streams, while ground-water discharge is to peren­ Uinta Mountains is less. nial streams. Hydraulic conductivity of the Duch­ Simulated hydraulic head compared well esne River-Uinta aquifer is related to lithology and with measured hydraulic head as described by a the degree of fracturing. coefficient of variation of 0.97. The root-mean- squared residual was 187 feet, smaller than the Ground water in the Duchesne River-Uinta 202 feet criterion determined by variogram analy­ aquifer exists within both local and basin flow sys­ ses. This difference between calculated and mea­ tems. The difference in hydraulic head expressed sured water levels shows that basin variations in by measurements less than 5 miles apart is caused transmissivity, recharge, and discharge are ade­ by local hydrologic effects. The difference in quately described. hydraulic head expressed by measurements sepa­ rated by 5 to 40 miles is caused by both local and basin effects. The difference in hydraulic head INTRODUCTION expressed by measurements greater than 40 miles apart is caused by basin effects. The Duchesne River-Uinta aquifer is an impor­ Basin geohydrologic characteristics of the tant source of ground water for irrigation, domestic, Duchesne River-Uinta aquifer are described by a and industrial use within the Uinta Basin of Utah and steady-state flow model that simulates about Colorado (fig. 1). The Duchesne River-Uinta aquifer 4,190 square miles of area with regular node spac­ includes both the Duchesne River Formation of late ing of 2.5 miles. Simulated recharge from precip­ Eocene and early Oligocene age and the Uinta Forma­ itation is 262 cubic feet per second. Recharge in tion of late Eocene age, because these two formations the southern part of the model area is less than pre­ act as a single geohydrologic unit and interfinger at the viously calculated while recharge in areas adjacent east and west ends of the basin (Hood, 1976; L.J. to the Uinta Mountains is greater. Simulated Martin, U.S. Geological Survey, written commun., 1986). Ground water in the aquifer exists under a com­ ground-water recharge from the Green River is plex system of shallow water-table, perched, and deep about 8 cubic feet per second; ground-water dis­ artesian conditions. charge to the Uinta River is about 45 cubic feet per Hydrologic studies previously