Currents in Clear Lake

EPA Grant Number: R825433C053
Subproject: this is subproject number 053 , 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: Currents in Clear Lake
Investigators: Schladow, S. G.
Institution: University of California - Davis
EPA Project Officer: Levinson, Barbara
Project Period: June 30, 1995 through June 30, 1998
RFA: Exploratory Environmental Research Centers (1992) RFA Text |  Recipients Lists
Research Category: Center for Ecological Health Research , Targeted Research


Water motions play a fundamental role in the transport of nutrients and pollutants from sources to locations where organisms are exposed to their effects. In the case of Clear Lake, transport of Hg away from its source at Sulphur Bank Mine is of particular concern. Although bulk inorganic mercury is concentrated near the mine, body burdens of Hg tend to be much more evenly distributed. Some combination of transport or non-linear relationship of exposure to inorganic Hg concentration and physical transport of Hg must account for the lakewide levels of exposure.


Investigations of currents using doppler acoustic current meters and dye markers at Clear Lake have demonstrated a large and unexpected effect of diurnal stratification on water motions. In the investigators summer experiment, a vigorous two-layer flow existed, with a bottom current flowing from the more polluted sediments in the Oaks Arm of the lake towards the larger Upper Arm. In winter, the absence of stratification was accompanied by a much less vigorous exchange between the more and less highly polluted parts of the system.

Lake current systems are difficult to characterize because currents take on the order of 100 hours to reach equilibrium with a given wind forcing, while wind forcing varies dramatically on the 24 hr cycle and less deterministically between days. Currents are never in equilibrium, and every sampling experiment tends to be a unique snapshot that never exactly repeats itself. An important question to consider, particularly in light of this complexity, is how these basinscale exchanges impact the results of water sampling. With further study of the currents, it may be possible to better delineate the conditions under which sampling may give the most representative results.

Expected Results:

Investigators expect to combine current modeling investigations (with the help of the Decision Support Core) with a program of measurements designed to acquire enough data to verify the model's ability to mimic lake motions to an acceptable level of approximation. They will also experiment with using instruments that can be deployed in the lake for long periods (thermistor chains and water level recorders) to measure variables that respond to water motions, so that we can generalize beyond the relatively few experiments where direct measurement of currents is possible. Our ultimate objective is a well-verified model that can be forced with a wind realistic pattern and run for enough sample days to estimate average transport in the different seasons of the year.

Supplemental Keywords:

Watershed, fate and transport, modeling, ecosystem stress, pesticides, Diazinon, Sacramento River, hydrologic model, California, groundwater., RFA, Scientific Discipline, Toxics, Geographic Area, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, mercury transport, Geochemistry, Environmental Chemistry, Restoration, HAPS, Fate & Transport, Environmental Microbiology, Microbiology, Biochemistry, 33/50, Aquatic Ecosystem Restoration, West Coast, Geology, Environmental Engineering, Engineering, fate and transport, mercury loading, fluid dynamics, Clear Lake, Sulphur Bank Mercury Mine, mining, mercury & mercury compounds, currents, Mercury Compounds, microbiological aspects

Progress and Final Reports:

1996 Progress Report

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