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Final Report: Regional Hydrogeology and Contaminant Transport in a Sierra Nevada Ecosystem
EPA Grant Number: R825433C034Subproject: this is subproject number 034 , established and managed by the Center Director under grant R825433
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: EERC - Center for Ecological Health Research (Cal Davis)
Center Director: Rolston, Dennis E.
Title: Regional Hydrogeology and Contaminant Transport in a Sierra Nevada Ecosystem
Investigators: Fogg, Graham
Institution: University of California - Davis
EPA Project Officer: Levinson, Barbara
Project Period: October 1, 1996 through September 30, 2000
RFA: Exploratory Environmental Research Centers (1992)
Research Category: Center for Ecological Health Research , Targeted Research
Description:
Objective:Characterization and analysis of hydrogeology and contaminant transport in any subsurface system is challenging and often requires the development of new modeling tools. The objective of this research project was to develop new methods and apply those methods to the analysis of groundwater flow and contaminant transport in the Lake Tahoe Basin and other basins.
Summary/Accomplishments (Outputs/Outcomes):We developed a new, geostatistical method for characterizing and modeling subsurface heterogeneity, which is key to many contamination problems. The method, which is contained in a package of computer codes known as transition probability geostatistics (TPROGS), has been distributed freely to many groundwater investigators and researchers since 1999. In addition, we developed a highly efficient and accurate transport modeling scheme and computer code, known as random-walk particle method (RWHET), based on a new, random-walk particle technique. RWHET makes it possible, for the first time, to realistically model full, three-dimensional, heterogeneous groundwater transport processes. We used these two research developments to create and test a new method for determining groundwater’s susceptibility to contamination.
This research project also involved regional sampling of precipitation and shallow groundwater for methyl tertiarybutyl ether (MTBE) analysis, and collecting and documenting information relating to MTBE occurrence in the vicinity of leaking underground fuel tank (LUFT) sites. We found that gasoline LUFT sites that have MTBE-contaminated groundwater essentially are ubiquitous in the Lake Tahoe Basin. The presence of low levels of MTBE in Pope Marsh groundwater strongly indicates that pollutants from the lake can be transported into the marsh via groundwater.
Modeling analysis of the long-term persistence of MTBE in South Tahoe Basin groundwater, owing to past releases, showed that even if the sources are short lived (e.g., 1-5 years), the long-term consequences are considerable. This is because of the very high solubility of MTBE, its tendency not to biodegrade appreciably below the water table, and migration of water containing MTBE into fine-grained deposits (e.g., silts and clays) from which it can bleed back out slowly, serving as a long-term source for decades.
An important component of characterizing groundwater quality is getting an accurate groundwater temperature profile. In the final portion of our research project, we measured temperature profiles in numerous wells in the Tahoe Basin region. Many wells exhibit subsurface temperature inversions. Such temperature inversions can result from decadal and longer scale surface temperature warming trends. We demonstrated that such temperature inversions also can result from rapid lateral groundwater flow that has recharged at higher elevations where temperatures are cooler. The shape of these temperature profiles constrains the history of surface warming and/or the profile of groundwater flow velocity. Temperature profiles within unsaturated zones, especially deep unsaturated zones (extending greater than 50' below ground surface), often are measurably perturbed by recharge water moving downward through the unsaturated zone. We have succeeded in using this approach to estimate groundwater recharge rates (below the root zone) in several areas using temperature profile data.
The following activities were accomplished:
• We developed a new, quantitative geologic method for characterizing subsurface heterogeneity that is important for contaminant transport investigations. Contained in a package of computer codes called TPROGS, this method is increasingly in demand by groundwater investigators in government agencies, research laboratories, academia, and environmental consulting. Much of TPROGS has been incorporated into a popular groundwater modeling package (groundwater modeling system).
• We developed a new, highly efficient transport modeling algorithm and code for realistically simulating three-dimensional fate and transport of groundwater contaminants, including the effects of matrix diffusion on groundwater remediation and long-term sustainability of groundwater quality. Like TPROGS, this code is in demand from a variety of users and is being adopted by the U.S. Geological Survey for their popular MODFLOW-2000 modeling codes.
• We developed a much improved set of methods for estimating the susceptibility of groundwater systems to contamination. These methods are of integral importance to the U.S. Environmental Protection Agency's and several states' ongoing efforts to perform well head protection assessments and to set groundwater protection strategies.
• We gained important, but disturbing, insights into how basin-scale groundwater quality likely is to change over long time periods, when nonpoint and point sources of contamination persist for several decades. Results indicate that in many groundwater basins in California and the Western United States that have been subject to significant contaminant sources: (1) maximum effects of contaminant sources originating circa the 1940s have not necessarily occurred yet; (2) the rise in observed groundwater contamination that started in the last quarter of the 20th century appears to be just the beginning of a long-term, worsening trend in groundwater quality; and (3) the long lag time between "cause and effect" may preclude or significantly delay any regional, beneficial effects of source cleanup or other mitigative actions.
• Use of the tools described above, as well as the concepts for analysis of fate and transport of MTBE in the Tahoe Basin in 1998-2002, helped to identify a growing problem caused by leakage of fuels from underground storage tanks. We identified and examined possible sources of the MTBE, the potential longevity of this problem, and impacts on South Tahoe's groundwater management strategies. In 1998, the Governor of California used the conclusions of our study, which included a statewide analysis of the effects of MTBE on groundwater, to initiate a phaseout of MTBE use as a fuel additive.
• We identified low levels of groundwater MTBE contamination in Pope Marsh (south shore of Lake Tahoe). This contamination was shown to originate from the lake, which recharges the marsh when groundwater pumping depletes the marsh's water levels.
• We refined and tested thermal methods for characterizing groundwater flow systems in fractured-rock, alpine settings in the Lake Tahoe Basin. Still-emerging results include the characterization of the origin and depth of circulation of groundwater that sustains Brockway Hot Springs on the north shore of Lake Tahoe. The application of these methods also is producing the first estimates of groundwater recharge through some of the mountain blocks in the basin.
Supplemental Keywords:ecosystem, ecosystem protection, environmental exposure and risk, geographic area, international cooperation, water, terrestrial ecosystems, aquatic ecosystem, aquatic ecosystem restoration, aquatic ecosystems and estuarine research, biochemistry, ecological effects, ecological indicators, ecological monitoring, ecology and ecosystems, environmental chemistry, restoration, state, water and watershed, watershed, watershed development, watershed land use, watershed management, watershed modeling, watershed restoration, watershed sustainability, agricultural watershed, exploratory research environmental biology, California, CA, Clear Lake, Lake Tahoe, anthropogenic effects, aquatic habitat, biogeochemical cycling, ecological assessment, ecology assessment models, ecosystem monitoring, ecosystem response, ecosystem stress, environmental stress, environmental stress indicators, fish habitat, hydrologic modeling, hydrology, integrated watershed model, lake ecosystems, lakes, land use, nutrient dynamics, nutrient flux, water management options, water quality, wetlands. , Ecosystem Protection/Environmental Exposure & Risk, Water, INTERNATIONAL COOPERATION, Scientific Discipline, Waste, RFA, ECOSYSTEMS, Remediation, Water & Watershed, Restoration, Aquatic Ecosystem Restoration, Aquatic Ecosystems & Estuarine Research, Terrestrial Ecosystems, Aquatic Ecosystem, Biochemistry, Environmental Microbiology, Fate & Transport, Watersheds, Ecology and Ecosystems, ecological impact, contaminant transport models, fate and transport, geochemistry, watershed management, watershed restoration, ecological research, ecology assessment models, MTBE, aquifer fate and treatment, aquatic habitat protection , groundwater, land use, wetland restoration, Lake Tahoe, hydrologic processes, contaminant exposure, contaminant biodegradation rates, aquatic ecosystems, environmental stress, biogeochemical study, watershed sustainablility, contaminated groundwater, hydrology, Sierra Nevada, restoration strategies, ecosystem stress, biodiversity, biogeochemical cycling, integrated watershed model
Relevant Websites:
Progress and Final Reports:
1999 Progress Report
Original Abstract
Main Center Abstract and Reports:
R825433 EERC - Center for Ecological Health Research (Cal Davis)
Subprojects under this Center:
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R825433C001 Potential for Long-Term Degradation of Wetland Water Quality Due to Natural Discharge of Polluted Groundwater
R825433C002 Sacramento River Watershed
R825433C003 Endocrine Disruption in Fish and Birds
R825433C004 Biomarkers of Exposure and Deleterious Effect: A Laboratory and Field Investigation
R825433C005 Fish Developmental Toxicity/Recruitment
R825433C006 Resolving Multiple Stressors by Biochemical Indicator Patterns and their Linkages to Adverse Effects on Benthic Invertebrate Patterns
R825433C007 Environmental Chemistry of Bioavailability in Sediments and Water Column
R825433C008 Reproduction of Birds and mammals in a terrestrial-aquatic interface
R825433C009 Modeling Ecosystems Under Combined Stress
R825433C010 Mercury Uptake by Fish
R825433C011 Clear Lake Watershed
R825433C012 The Role of Fishes as Transporters of Mercury
R825433C013 Wetlands Restoration
R825433C014 Wildlife Bioaccumulation and Effects
R825433C015 Microbiology of Mercury Methylation in Sediments
R825433C016 Hg and Fe Biogeochemistry
R825433C017 Water Motions and Material Transport
R825433C018 Economic Impacts of Multiple Stresses
R825433C019 The History of Anthropogenic Effects
R825433C020 Wetland Restoration
R825433C021 Sierra Nevada Watershed Project
R825433C022 Regional Transport of Air Pollutants and Exposure of Sierra Nevada Forests to Ozone
R825433C023 Biomarkers of Ozone Damage to Sierra Nevada Vegetation
R825433C024 Effects of Air Pollution on Water Quality: Emission of MTBE and Other Pollutants From Motorized Watercraft
R825433C025 Regional Movement of Toxics
R825433C026 Effect of Photochemical Reactions in Fog Drops and Aerosol Particles on the Fate of Atmospheric Chemicals in the Central Valley
R825433C027 Source Load Modeling for Sediment in Mountainous Watersheds
R825433C028 Stress of Increased Sediment Loading on Lake and Stream Function
R825433C029 Watershed Response to Natural and Anthropogenic Stress: Lake Tahoe Nutrient Budget
R825433C030 Mercury Distribution and Cycling in Sierra Nevada Waterbodies
R825433C031 Pre-contact Forest Structure
R825433C032 Identification and distribution of pest complexes in relation to late seral/old growth forest structure in the Lake Tahoe watershed
R825433C033 Subalpine Marsh Plant Communities as Early Indicators of Ecosystem Stress
R825433C034 Regional Hydrogeology and Contaminant Transport in a Sierra Nevada Ecosystem
R825433C035 Border Rivers Watershed
R825433C036 Toxicity Studies
R825433C037 Watershed Assessment
R825433C038 Microbiological Processes in Sediments
R825433C039 Analytical and Biomarkers Core
R825433C040 Organic Analysis
R825433C041 Inorganic Analysis
R825433C042 Immunoassay and Serum Markers
R825433C043 Sensitive Biomarkers to Detect Biochemical Changes Indicating Multiple Stresses Including Chemically Induced Stresses
R825433C044 Molecular, Cellular and Animal Biomarkers of Exposure and Effect
R825433C045 Microbial Community Assays
R825433C046 Cumulative and Integrative Biochemical Indicators
R825433C047 Mercury and Iron Biogeochemistry
R825433C048 Transport and Fate Core
R825433C049 Role of Hydrogeologic Processes in Alpine Ecosystem Health
R825433C050 Regional Hydrologic Modeling With Emphasis on Watershed-Scale Environmental Stresses
R825433C051 Development of Pollutant Fate and Transport Models for Use in Terrestrial Ecosystem Exposure Assessment
R825433C052 Pesticide Transport in Subsurface and Surface Water Systems
R825433C053 Currents in Clear Lake
R825433C054 Data Integration and Decision Support Core
R825433C055 Spatial Patterns and Biodiversity
R825433C056 Modeling Transport in Aquatic Systems
R825433C057 Spatial and Temporal Trends in Water Quality
R825433C058 Time Series Analysis and Modeling Ecological Risk
R825433C059 WWW/Outreach
R825433C060 Economic Effects of Multiple Stresses
R825433C061 Effects of Nutrients on Algal Growth
R825433C062 Nutrient Loading
R825433C063 Subalpine Wetlands as Early Indicators of Ecosystem Stress
R825433C064 Chlorinated Hydrocarbons
R825433C065 Sierra Ozone Studies
R825433C066 Assessment of Multiple Stresses on Soil Microbial Communities
R825433C067 Terrestrial - Agriculture
R825433C069 Molecular Epidemiology Core
R825433C070 Serum Markers of Environmental Stress
R825433C071 Development of Sensitive Biomarkers Based on Chemically Induced Changes in Expressions of Oncogenes
R825433C072 Molecular Monitoring of Microbial Populations
R825433C073 Aquatic - Rivers and Estuaries
R825433C074 Border Rivers - Toxicity Studies