PREDICTING GROUNDWATER FLOW AND TRANSPORT WITH NUMERICAL MODELS AND ENVIRONMENTAL TRACERS

Groundwater flow and transport processes strongly influence and are inextricably linked to the integrated hydrologic and biogeochemical dynamics within catchments. Yet, groundwater system understanding and model predictions remain uncertain owing to the unknown subsurface property distributions, errors in atmospheric forcing conditions, and limited observations to constrain groundwater fluxes. In this dissertation we investigate the use of environmental tracer observations that inform hydrological processes over broad timescales to reduce uncertainties in groundwater transport prediction uncertainties. We further develop environmental tracer data assimilation and uncertainty quantification techniques to enhance integrated hydrological and groundwater process understanding at two distinct field sites: a semi-arid region in central Wyoming with minimal topography, and a snow-dominated mountain catchment in Colorado. Environmental tracer observations are typically used to derive “apparent” groundwater ages, which require assumptions regarding the residence time distribution of a sample. We demonstrate reductions in permeability and infiltration rate parameter uncertainties when using environmental tracer concentrations, rather than apparent age, to calibrate a numerical model of a field site located near Riverton, Wyoming. We then extend the model uncertainty analysis technique to robustly quantify the full parameter joint posterior distributions with Markov-chain Monte Carlo (MCMC) sampling and Bayes’ theorem. To circumvent the intractable computational expense required by the MCMC method, we train a computationally frugal Artificial Neural Network to emulate the process-based groundwater transport model. We show that the parameter inference that assimilates 3H observations reduce the uncertainty in the permeability field and infiltration rates, relative to assimilating hydraulic head observations alone. However, CFC-12 transport predictive uncertainties do not reproduce the validation dataset, highlighting the influence of model and observation data structural errors on the parameter inference. Uncertainties in environmental tracer interpretations are further investigated using an observation dataset (3H, SF6, CFC’s, and 4He) sampled from bedrock groundwater wells in the East River Watershed near Crested Butte, Colorado. We develop MCMC techniques to quantify uncertainties in the noble gas recharge thermometry parameters and the resulting groundwater residence time distributions. The inferred residence time distributions suggest that the shallow bedrock groundwater contains a mixture of waters characterized by residence times that are modern (\u3c70 years) and pre-modern (\u3e70 years). The findings that shallow fractured bedrock hosts groundwater with residence times ranging from decades to centuries informs the integrated conceptual model of how mountain systems store and transmit essential water resources, and how these resources will respond to perturbations in the hydrologic cycle

PolySat Helmholtz Cage

The MagCal5 Helmholtz cage project is an interdisciplinary approach to provide the PolySat/CubeSat research lab with a magnetic testing environment for the calibration of magnetic components and verification of various control laws. The Cal Poly CubeSat organization is the home of the CubeSat Specification, and acts as a testing and integration facility for CubeSats built by universities across the world. The PolySat organization is a CubeSat developer that works with numerous industry partners to design, manufacture, and operate CubeSats to further scientific advancement. The addition of a magnetic test stand to the lab will allow CubeSat to extend to the range of testing it can provide to other universities and will allow PolySat to perform more extensive attitude determination and control system testing on their CubeSats before they are put into orbit

A late Wisconsin (32–10k cal a BP) history of pluvials, droughts and vegetation in the Pacific south-west United States (Lake Elsinore, CA)

Continuous, sub-centennially resolved, paleo terrestrial records are rare from arid environments such as the Pacific south-west United States. Here, we present a multi-decadal to centennial resolution sediment core (Lake Elsinore, CA) to reconstruct late Wisconsin pluvials, droughts and vegetation. In general, the late Wisconsin is characterized by a wetter and colder climate than during the Holocene. Specifically, conditions between 32.3 and 24.9k cal a BP are characterized by large-amplitude hydrologic and ecologic variability. Highlighting this period is a ∼2000-year glacial mega-drought (27.6–25.7k cal a BP) during which the lake shallowed (3.2–4.5 m depth). This period is approximately coeval with a Lake Manix regression and an increase in xeric vegetation in the San Bernardino Mountains (Baldwin Lake). The Local Last Glacial Maximum (LLGM) is bracketed between 23.3 and 19.7k cal a BP − a ∼3000-year interval characterized by reduced run-off (relative to the glacial), colder conditions and vegetative stability. Maximum sustained wetness follows the LLGM, beginning at 19.7 and peaking by 14.4k cal a BP. A two-step decrease in runoff characterizes the Lateglacial to Holocene transition; however, the vegetation change is more complex, particularly at the beginning of the Younger Dryas chronozone. By 12.6–12.4k cal a BP, the climate achieved near Holocene conditions

Investigating the Use of Environmental Chemical Tracer Concentrations to Reduce the Uncertainty of Modeled Groundwater Flow and Transport in a Fractured Rock System

Groundwater flow and transport within fractured rock systems has important implications for evaluating available subsurface water resources, the design of nuclear waste disposal systems, and identifying the role of groundwater in mountainous regions. The relative amount of water moving through a fractured zone compared to the surrounding rock matrix is often unknown. A principal uncertainty in simulating groundwater flow and solute transport within fractured rock is the characterization and explicit expression of the effective fracture parameters. Hydrogeologists have extensively utilized ‘apparent’ groundwater mean ages derived from environmental chemical tracer data to constrain subsurface flow and transport models. However, deriving a groundwater mean age from environmental tracer concentrations is ambiguous and uncertain. In this study we develop a 3D groundwater flow and solute transport simulation of the Bedrichov Tunnel in the Czech Republic to directly investigate the utility in utilizing environmental tracer concentrations, rather than inferred groundwater mean age, to constrain estimates of effective fractured rock parameters. The Bedrichov Tunnel simulation is on a portion of the tunnel that contains a single major fracture that has associated fracture discharge, stable isotope, and tritium measurements that span multiple years. Fracture and distributed tunnel discharge measurements, apparent ages of fracture discharge derived from environmental tracers, and the multiple environmental tracer concentrations are used to constrain the range of effective fracture and solid matrix parameters that control flow and transport to the Bedrichov Tunnel. We investigate the differences in estimated effective fracture parameter uncertainties when using environmental tracer concentrations and mean groundwater age to separately constrain the Bedrichov Tunnel groundwater flow and solute transport model. It is hypothesized that higher parameter uncertainties will be associated when groundwater age is utilized due to the bias and uncertainties associated with inferring a mean groundwater age from environmental tracers. This work will provide information on methods to assimilate and evaluate the information content of environmental tracer data in groundwater flow and transport models that can facilitate more accurate predictions of future subsurface hydrology conditions

Evaluation of the ground-water flow model for northern Utah Valey, Utah, updated to conditions through 2002

This report evaluates the performance of a numerical model of the ground-water system in northern Utah Valley, Utah, that originally simulated ground-water conditions during 1947-1980 and was updated to include conditions estimated for 1981-2002. Estimates of annual recharge to the groundwater system and discharge from wells in the area were added to the original ground-water flow model of the area.U. S. Department of the Interior, U. S. Geological Survey Scientific Investigations Report 2006- 5064 Prepared in cooperation with the Central Utah Water Conservancy District; Jordan Valley Water Conservancy District representing Draper City; Highland Water Company; Utah Department of Natural Resources, Division of Water Rights; and the municipalities of Alpine, American Fork, Cedar Hills, Eagle Mountain, Highland, Lehi, Lindon, Orem, Pleasant Grove, Provo, Saratoga Springs, and Vineyard Evaluation of the Ground- Water Flow Model for Northern Utah Valley, Utah, Updated to Conditions through 2002 89 15 15 89 Eagle Mountain Traverse Camp Williams Mountains Salt Lake Valley Jordan reviR Dry Creek Utah Lake Cedar Hills Lehi Vineyard Orem Provo Springville Saratoga Springs Hobble Creek Spanish Fork Spanish Fork River Provo Bay Lindon Provo River Range Wasatch Pleasant Grove River Fork American Alpine Highland American Fork Northern Utah Valley Lake Mountains Mountain West Riverton Draper Cedar Valley Mt Timpanogos 11,750 feet Cover: View looking east toward American Fork Canyon in Utah County, Utah, March 2004. Evaluation of the Ground- Water Flow Model for Northern Utah Valley, Utah, Updated to Conditions through 2002 By Susan A. Thiros Prepared in cooperation with the Central Utah Water Conservancy District; Jordan Valley Water Conservancy District representing Draper City; Highland Water Company; Utah Department of Natural Resources, Division of Water Rights; and the municipalities of Alpine, American Fork, Cedar Hills, Eagle Mountain, Highland, Lehi, Lindon, Orem, Pleasant Grove, Provo, Saratoga Springs, and Vineyard Scientific Investigations Report 2006- 5064 U. S. Department of the Interior U. S. Geological Survey U. S. Department of the Interior Gale A. Norton, Secretary U. S. Geological Survey P. Patrick Leahy, Acting Director U. S. Geological Survey, Salt Lake City, Utah: 2006 For additional information write to: U. S. Geological Survey Director, USGS Utah Water Science Center 2329 W. Orton Circle Salt Lake City, UT 84119- 2047 Email: GS- W- UTpublic- info@ usgs. gov URL: http:// ut. water. usgs. gov/ For product and ordering information: World Wide Web: http:// www. usgs. gov/ pubprod Telephone: 1- 888- ASK- USGS For more information on the USGS-- the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment: World Wide Web: http:// www. usgs. gov Telephone: 1- 888- ASK- USGS Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U. S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. iii Contents Abstract....................................................................................................................... .................................... 1 Introduction................................................................................................................... .................................. 1 Purpose and Scope ............................................................................................................................... 3 Description of the Study Area ............................................................................................................. 3 Ground- Water Hydrology ..................................................................................................................... 3 Description of the Model.......................................................................................................................... .... 5 Update of the Model to Conditions through 2002 ...................................................................................... 8 Performance of the Updated Model ........................................................................................................... 8 Potential Revisions and New Data to Improve the Updated Model .................................................... 15 Summary........................................................................................................................ ................................ 19 References Cited.......................................................................................................................... ................ 19 Figures Figure 1. Location of northern Utah Valley study area, Utah...................................................................... 2 Figure 2. Generalized block diagram showing the basin- fill deposits and ground- water system in northern Utah Valley, Utah............................................................................................................... 4 Figure 3. Grid for the model of the ground- water system in northern Utah Valley, Utah ...................... 6 Figure 4. Location of cells simulating recharge and discharge in the model of the ground- water system in northern Utah Valley, Utah............................................................................................. 7 Figure 5. Specified ground- water discharge from wells in the updated model of the ground- water system in northern Utah Valley, Utah, 1947- 2002......................................................................... 9 Figure 6. Location of cells simulating flowing and pumping wells in 1981 and 2002 in the updated model of the ground- water system in northern Utah Valley, Utah.......................................... 10 Figure 7. Annual streamflow in the American Fork and Provo Rivers and specified recharge to the ground- water system in the updated model of northern Utah Valley, Utah, 1947- 2002........................................................................................................................... .............. 11 Figure 8. Location of wells with measured and computed water- level changes in the updated model of the ground- water system in northern Utah Valley, Utah.......................................... 12 Figure 9. Measured water- level change for selected wells during 1981- 2003 and computed water- level change for the corresponding model cell and layer in the updated model of the ground- water system in northern Utah Valley, Utah...................................................... 13 Figure 10. Computed water- level decline from the end of 1980 to the end of 2001 in layer 5 of the updated model of the ground- water system and measured water- level decline from March 1981 to March 2002 at 14 wells that correspond to layer 5 in northern Utah Valley, Utah........................................................................................................................... ........... 16 Figure 11. Measured water- level altitude for selected wells during 1981- 2003 and computed water- level altitude for the corresponding cell and layer in the updated model of the ground- water system in northern Utah Valley, Utah. ................................................................ 17 Figure 12. Simulated and specified ground- water recharge and discharge in the updated model of the ground- water system in northern Utah Valley, Utah, 1947- 2002.................................. 18 iv Conversion Factors and Datums Multiply By To obtain Length foot ( ft) 0.3048 meter ( m) mile ( mi) 1.609 kilometer ( km) Area square mile ( mi2) 2.590 square kilometer ( km2) Volume acre- foot ( acre- ft) 1,233 cubic meter ( m3) Flow rate acre- foot per year ( acre- ft/ yr) 1,233 cubic meter per year ( m3/ yr) Vertical coordinate information is referenced to the North American Vertical Datum of 1929 ( NAVD 29). Horizontal coordinate information is referenced to the North American Datum of 1983 ( NAD 83). Altitude, as used in this report, refers to distance above the vertical datum. Table Table 1. Conceptual ground- water budget for the basin- fill aquifer system in northern Utah Valley, Utah........................................................................................................................... ............ 4 Evaluation of the Ground- Water Flow Model for Northern Utah Valley, Utah, Updated to Conditions through 2002 By Susan A. Thiros Abstract This report evaluates the performance of a numerical model of the ground- water system in northern Utah Valley, Utah, that originally simulated ground- water conditions during 1947- 1980 and was updated to include conditions estimated for 1981- 2002. Estimates of annual recharge to the ground-water system and discharge from wells in the area were added to the original ground- water flow model of the area. The files used in the original transient- state model of the ground- water flow system in northern Utah Valley were imported into MODFLOW- 96, an updated version of MODFLOW. The main model input files modified as part of this effort were the well and recharge files. Discharge from pumping wells in northern Utah Valley was estimated on an annual basis for 1981- 2002. Although the amount of average annual withdrawals from wells has not changed much since the previous study, there have been changes in the distribution of well discharge in the area. Discharge estimates for flowing wells during 1981- 2002 were assumed to be the same as those used in the last stress period of the original model because of a lack of new data. Variations in annual recharge were assumed to be proportional to changes in total surface- water inflow to northern Utah Valley. Recharge specified in the model during the additional stress periods varied from 255,000 acre- feet in 1986 to 137,000 acre- feet in 1992. The ability of the updated transient- state model to match hydrologic conditions determined for 1981- 2002 was evalu-ated by comparing water- level changes measured in wells to those computed by the model. Water- level measurements made in February, March, or April were available for 39 wells in the modeled area during all or part of 1981- 2003. In most cases, the magnitude and direction of annual water- level change from 1981 to 2002 simulated by the updated model reason-ably matched the measured change. The greater- than- normal precipitation that occurred during 1982- 84 resulted in period-of- record high water levels measured in many of the observa-tion wells in March 1984. The model- computed water levels at the end of 1982- 84 also are among the highest for the period. Both measured and computed water levels decreased during the period representing ground- water conditions from 1999 to 2002. Precipitation was less than normal during 1999- 2002. The ability of the model to adequately simulate cli-matic extremes such as the wetter- than- normal conditions of 1982- 84 and the drier- than- normal conditions of 1999- 2002 indicates that the annual variation of recharge to the ground-water system based on streamflow entering the valley, which in turn is primarily dependent upon precipitation, is appropri-ate but can be improved. The updated transient- state model of the ground- water system in northern Utah Valley can be improved by making revisions on the basis of currently avail-able data and information. Introduction Ground water is the primary source of drinking water in northern Utah Valley, Utah, and withdrawals for public supply have increased because of rapid population growth. Increased withdrawals coupled with drought conditions during 1999- 2004 caused water levels in many wells in the area to decline to their lowest recorded levels ( Burden and others, 2004, p. 40- 41). Water- level declines may affect the ability of water managers to withdraw water from public- supply wells or may affect the discharge to springs, drains, streams, Utah Lake, and flowing wells in lower parts of the valley. The effects of with-drawals and modifications to the current hydrologic system are not known, but need to be understood in order to manage and protect the ground- water resource. The U. S. Geological Survey began a 4- year study of the ground- water system in northern Utah Valley, Utah ( fig. 1), in 2003 in cooperation with the Central Utah Water Conservancy District; Jordan Valley Water Conservancy District represent-ing Draper City; Highland Water Company; Utah Depart-ment of Natural Resources, Division of Water Rights; and the municipalities of Alpine, American Fork, Cedar Hills, Eagle Mountain, Highland, Lehi, Lindon, Orem, Pleasant Grove, Provo, Saratoga Springs, and Vineyard. The objectives of this study are to develop a better understanding of the ground-water system and to provide information to help determine potential effects of withdrawals on water levels, water quality, and natural ground- water discharge in northern Utah Valley. A new aerially expanded model of the ground- water system in northern Utah Valley is currently ( 2006) being constructed. 89 15 15 89 Eagle Mountain Traverse Camp Williams Mountains Salt Lake Valley Jordan River Dry Creek Utah Lake Cedar Hills Lehi Vineyard Orem Provo Springville Saratoga Springs Hobble Creek Spanish Fork Spanish Fork River Provo Bay Lindon EXPLANATION Boundary of active cells in the model ( Clark, 1984) of the ground- water system in northern Utah Valley Approximate boundary of basin- fill deposits Provo River Range Wasatch Pleasant Grove River Fork American Alpine Highland American Fork Northern Utah Valley Lake Mountains Mountain West Riverton Draper Cedar Valley Mt Timpanogos 11,750 feet 112 degrees 0' 111 degrees 35' 0 2 4 6 8 10 Miles 0 2 4 6 8 10 Kilometers 40 degrees 30' 40 degrees 5' Colorado River UTAH Study area Great Salt Lake Figure 1. Location of northern Utah Valley study area, Utah. 2 Evaluation of the Ground- Water Flow Model for Northern Utah Valley, Utah, Updated to Conditions through 2002 The original model ( Clark, 1984) was updated and evalu-ated as part of this study in order to determine how well it simulated ground- water conditions during periods of climatic extremes and to use this information in the construction of the new model. Ground- water flow models can be used by water managers to help understand impacts to the ground- water system from increased development, changing water use, and changes in recharge. Purpose and Scope This report evaluates the performance of a numerical model of the ground- water system in northern Utah Valley, Utah, that originally simulated conditions during 1947- 1980 ( Clark, 1984) and was updated to include ground- water condi-tions estimated for 1981- 2002. Estimates of annual recharge to the ground- water system and discharge from wells in the area were added to the original ground- water flow model of the area. The ability of the updated transient- state model to match hydrologic conditions determined for 1981- 2002 was evaluated by comparing water- level changes measured in wells to those computed by the model. This period includes both a wet and a dry sequence of years that resulted in the highest and lowest water levels measured in most wells with long peri-ods of record in northern Utah Valley. Numerical models of ground- water systems are constructed on the basis of available information and data, and if new data or information become available, testing the performance of a model against those data will result in a better understanding of the model and the ground- water system ( Konikow and Bredehoeft, 1992). The performance of the updated model provides information that can be used to guide the study for updating and improving the model and for additional data collection. This assessment also provides valuable information to users of the original model while the new model is being developed. Description of the Study Area The study area covers the northern part of Utah Valley in the north- central part of Utah and corresponds to the extent of basin- fill deposits ( fig. 1). It includes the northern part of Utah Lake, a natural, large ( about 150 mi2), shallow ( 9.5 ft average depth) lake in the lowest part of the valley. Northern Utah Valley is bounded on the north by the Traverse Moun-tains, on the east by the Wasatch Range, and on the west by the Lake Mountains. The boundary between the northern and southern parts of Utah Valley is arbitrarily located near Provo Bay. Ground water occurring north of this boundary generally discharges in northern Utah Valley and ground water occurring south of this boundary generally discharges in southern Utah Valley. The boundary is poorly defined through Utah Lake because of lack of data. The land- surface altitude of the basin- fill deposits in the area ranges from 4,489 ft, the level of Utah Lake set by court decree as the maximum legal storage level, above which control gates for diversions are required to be fully opened ( compromise level), to about 5,160 ft at the highest level of prehistoric Lake Bonneville deposits along the mountain sides. Mount Timpanogos in the adjacent Wasatch Range reaches an altitude of 11,750 ft and provides runoff to two major streams that enter northern Utah Valley, the American Fork and Provo Rivers. The population in northern Utah Valley increased from 170,000 in 1980 to 282,000 in 2000, a 66 percent change, and land is rapidly being converted from agricultural to urban uses to accommodate this growth. Prior to these recent changes in land use, the area had water- use patterns associated with agricultural diversions from streams and withdrawals from wells. Changing water- use patterns have the potential to affect ground- water quantity and quality because the location of withdrawals may change and mountain- front streamflow previously used for irrigation will likely be used for munici-pal supply. Recharge to the ground- water system will likely be reduced because of less seepage from irrigated fields and canals as agricultural areas are converted to residential areas. Mountain- front streams could become piped and diverted upstream from the valley for public supply, also resulting in less recharge to the ground- water system. Ground- Water Hydrology The ground- water system in northern Utah Valley con-sists of aquifers contained in unconsolidated sediments of Tertiary and Quaternary age that have filled the basin between the surrounding mountains and in consolidated rock in the mountains. The Wasatch Range and the Traverse and Lake Mountains, which are composed primarily of fractured quartz-ite, limestone, and shale, receive varying amounts of recharge from precipitation. Almost all of the wells in the valley are completed in the basin- fill deposits; therefore, it is considered the principal ground- water aquifer in the study area. Several wells have been recently completed in the consolidated rock along the margins of the valley to provide water for public supply. Clark and Appel ( 1985) described the principal ground-water system in northern Utah Valley as consisting of three generally distinct aquifers consisting of predominantly coarser- grained sediment separated by confining layers of clay ( fig. 2). The first major aquifer is the shallow artesian aquifer in deposits of Pleistocene age and is typically overlain by blue clay about 50- 100 ft below the valley surface that thins and pinches out near the valley margins. Another fine- grained sequence separates the shallow from the deep artesian aquifer of Pleistocene age at about 150 ft below land surface. A few wells penetrate to depths greater than 500 ft below land sur-face in the valley and are completed in the underlying deposits of Quaternary/ Tertiary age. Water levels in wells generally indicate an upward gradient between the confined aquifers. The confining layers become thin or discontinuous near the mountain fronts, resulting in the basin- fill aquifers not being Introduction 3 differentiated by depth and ground water occurring under unconfined conditions. A shallow unconfined aquifer overlies the uppermost artesian aquifer and can be within a few feet of the land surface in the lower parts of the valley. Recharge to the basin- fill aquifers is from subsurface inflow from the surrounding consolidated rocks, in addition to losses from streams and canals ( table 1) in the primary recharge area ( fig. 2). Ground- water discharge is primarily to wells, drains, and springs in and around Utah Lake. The differ-ence between the totals for recharge and discharge is mainly the result of insufficient data ( Clark and Appel, 1985, p. 85) and changes in the amount of ground water in storage. The value listed for each budget component represents an average annual amount. Data were not available to calculate average values for all components for the same time period. Table 1. Conceptual ground- water budget for the basin- fill aquifer system in northern Utah Valley, Utah ( from Clark and Appel, 1985, table 18) Budget component Acre- feet per year Recharge Seepage from natural channels and irrigation canals 73,000 Seepage from irrigated fields, lawns, gardens, and direct precipitation 15,000 Subsurface inflow from mountains 112,000 Recharge total 200,000 Discharge Wells 68,000 Drains, springs, and waterways 135,000 Diffuse seepage to Utah Lake 7,000 Evapotranspiration 8,000 Subsurface outflow through Jordan Narrows 2,000 Discharge total 220,000 Figure 2. Generalized block diagram showing the basin- fill deposits and ground- water system in northern Utah Valley, Utah. Consolidated rock

Hydrogeology of shallow basin-fill deposits in areas of Salt Lake Valley, Salt Lake County, Utah

As part of the National Water-Quality Assessment (NAWQA) program, the U.S. Geological Survey (USGS) studied the effects of human activities on the quality of shallow ground water in areas with recently developed urban land use in Salt Lake Valley, Utah, an urban area within the Great Salt Lake Basins study unit (fig. 1). Pioneers first settled Salt Lake Valley in 1847, and an irrigation system was developed soon after to grow crops in the semiarid climate. Agricultural and undeveloped areas in the valley were converted to residential and commercial uses as the population increased to about 850,000 in 1999 (U.S. Census Bureau, written commun., 2000). The study was done from 1999 to 2001 in recently developed residential/commercial areas of the valley in which shallow ground water has the potential to move to a deeper aquifer that is used for public supply

Quality and sources of shallow ground water in areas of recent residential development in Salt Lake Valley, Salt Lake County, Utah

Residential and commercial development of about 80 square miles that primarily replaced undeveloped and agricultural areas occurred in Salt Lake Valley, Utah, from 1963 to 1994. This study evaluates the occurrence and distribution of natural and anthropogenic compounds in shallow ground water underlying recently developed (post 1963) residential and commercial areas. Monitoring wells from 23 to 153 feet deep were installed at 30 sites. Water-quality data for the monitoring wells consist of analyses of field parameters, major ions, trace elements, nutrients, dissolved organic carbon, pesticides, and volatile organic compounds

Quantifying Subsurface Parameter Uncertainties with Surrogate Modeling and Environmental Tracers

Identifying the uncertainty in predictions made by groundwater flow and transport numerical models is critical for effective water resource management and contaminated site remediation. In this work, we combine physics-based groundwater reactive transport modeling with data-driven machine learning techniques to quantify hydrogeologic model uncertainties for a site in Wyoming, USA. We train a deep artificial neural network (ANN) on a training dataset that consists of groundwater hydraulic head and environmental tracer concentration (3H, SF6, and CFC-12) fields generated using a high-fidelity groundwater reactive transport model. Inputs of the training dataset and reactive transport model include variable and uncertain hydrogeologic properties, recharge rates, and stream boundary conditions. Using the trained ANN as a surrogate to reproduce the input-output response of the reactive transport model, we quantify the full posterior distributions in predicted model hydrogeologic parameters and hydraulic forcing conditions using Markov-chain Monte Carlo (MCMC) calibration and field observations of groundwater hydraulic heads and environmental tracers. The coupling of the physics-based reactive transport model with the machine learning surrogate model allows us to efficiently quantify model uncertainties, which is typically computationally intractable using reactive transport models alone. This technique can be used to help improve hydrogeologists\u27 ability to assimilate field observations into subsurface numerical model calibration procedures and improve prediction uncertainty quantification

Evaluation of the ground-water flow model for northern Utah Valley, Utah, updated to conditions through 2002

This report evaluates the performance of a numerical model of the ground-water system in northern Utah Valley, Utah, that originally simulated ground-water conditions during 1947-1980 and was updated to include conditions estimated for 1981-2002. Estimates of annual recharge to the groundwater system and discharge from wells in the area were added to the original ground-water flow model of the area

Hydrogeology of shallow basin-fill deposits in areas of Salt Lake Valley, Salt Lake County, Utah /

"National Water-Quality Assessment Program."One folded colored map in pocket.Includes bibliographical references (p. 22-23).Title of map in pocket: Well logs and water-level hydrographs, Salt Lake Valley, Utah.Mode of access: Internet