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Final Report: Water Motions and Material Transport
EPA Grant Number: R825433C017Subproject: this is subproject number 017 , 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: Water Motions and Material Transport
Investigators: Schladow, S. G.
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:The objective of this project was to understand the physical processes of water circulation, transport, and mixing in Clear Lake, specifically in the Oaks Arm of Clear Lake near the main source of mercury—the Herman Pit. This research project was motivated by the fact that the general circulation of Clear Lake plays a key role in redistributing mercury throughout the lake. The source of mercury in the lake is the adjacent Sulphur Bank Mercury Mine, a U.S. Environmental Protection Agency Superfund site. To understand how mercury is chemically transformed and then transferred trophically through the food web, as well as to develop and assess remediation strategies, it is necessary to understand the mechanisms by which mercury is physically transported throughout the lake. This research project had two major components. The first component involved a field measurement in which we measured the physical flows that dominate the lake and described their driving forces. The second component involved the development of a three-dimensional numerical model to describe the complex flow field.
Summary/Accomplishments (Outputs/Outcomes):Through two intensive field studies, we showed that the dynamics of the Oaks Arm are characterized by a marked diurnal periodicity dictated by the wind regime. The wind acts during the afternoon and evening hours on this weakly stratified system to generate horizontal temperature gradients. During the night and early morning hours, when the wind forcing is negligible, the baroclinic pressure gradients that result from the horizontal differences in temperature become the dominant forcing mechanism in the system. These pressure gradients drive currents of up to 10-15 cm s-1 westward at the surface and eastward near the bottom. The setup and relaxation processes, modulated by the influence of the earth's rotation, create a residual cyclonic circulation, which facilitates the migration of mercury-laden particles to the other two arms of the lake.
In addition, we developed a three-dimensional model, SI3D-L, based on the continuity equation for incompressible fluids, the Reynolds-averaged form of the Navier-Stokes equations for momentum, the transport equation for temperature, and an equation of state relating temperature to fluid density. The numerical simulations confirmed the field observations, and provided many details that were not immediately evident in the data. Simulations allowed the quantification of the hydraulic exchange rates between the three basins, a result that explained the observed sediment mercury concentrations. The model also was used to quantify the effects of the very severe topography around Clear Lake on water motions and exchange rates.
The following activities were accomplished:
• We quantified mixing dynamics of a shallow, polymictic lake for the first time. Although this study has focused on a particular lake, the defining conditions of a relatively shallow water column, periodic wind forcing, and intermittent stratification that were found there are not unusual. Thus, the lake responses we describe (the absence of free oscillations, the transition from wind-driven circulation to density-driven circulation, and the mechanism of baroclinic pumping) should be observable at other locations. These responses vary greatly from those observed in deeper, seasonally stratified lakes, and they result in a more dynamic system.
• We developed a three-dimensional, public domain hydrodynamic model. We developed, calibrated, and validated the SI3D-L model using data from two extremely complex lakes (Clear Lake and Lake Tahoe). Unlike many commercial models, which receive little peer review, this model now has been the focus of several papers in leading journals. The model now can be used with great confidence by other investigators to describe motions in complex lake systems, study the fate of particulate material, and evaluate a range of restoration scenarios.
• We described and quantified the role of complex topography in wind-field modification. We showed quantitatively the extent to which topographical blocking of the wind field alters lake circulation and interbasin exchange rates. The neglect of such variations in a numerical model would add errors in excess of 20 percent.
• Using the model we developed, we showed that many important transport phenomena occur at night. Field sampling programs often are conducted during daylight hours. In the case of Clear Lake, this would have resulted in considerable bias in the results, as nighttime baroclinic relaxation is the dominant transport process. Using the information provided by the model, now it is possible to better design experiment programs in any lake.
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, Water & Watershed, Restoration, Aquatic Ecosystem Restoration, Aquatic Ecosystems & Estuarine Research, Terrestrial Ecosystems, Aquatic Ecosystem, Biochemistry, Environmental Microbiology, Fate & Transport, Watersheds, Monitoring/Modeling, Ecology and Ecosystems, Environmental Monitoring, ecological impact, fate and transport, watershed management, watershed restoration, Clear Lake, ecological research, ecology assessment models, aquatic habitat protection , wetland restoration, material transport, aquatic ecosystems, environmental stress, sediment transport, watershed sustainablility, water circulation, hydrology, watershed influences, restoration strategies, ecosystem stress, integrated watershed model
Relevant Websites:
Progress and Final Reports:
2000 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