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Final Report: Spatial and Temporal Trends in Water Quality
EPA Grant Number: R825433C057Subproject: this is subproject number 057 , 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: Spatial and Temporal Trends in Water Quality
Investigators: Jassby, Alan D.
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 research project was to investigate spatial and, especially, temporal variability in historical water quality data for the San Francisco Estuary and Lake Tahoe to understand the patterns, mechanisms, and practical implications for specific water resource problems. The research focused on the time scale of 1-100 years. This time scale is of particular interest from a practical viewpoint. It spans the period over which we must separate anthropogenic influences from natural variability to understand the effects of and modify our current use of water resources. It also spans the characteristic lengths for most instrumental time series that hold the key to this understanding.
Summary/Accomplishments (Outputs/Outcomes):A key part of our work involved collaboration with the Interagency Ecological Program (IEP) Environmental Monitoring Program for the San Francisco Bay-Delta and the Lake Tahoe Interagency Monitoring Program to refine the choice of monitoring variables, spatial and temporal monitoring frequency, and analytical methods. The data sets for both systems are unique in terms of their length and, in the case of the Bay-Delta, unique in terms of spatial coverage and comprehensiveness of water quality variables. Both databases are under pressure from financial constraints and a variety of users seeking different kinds of information. Modification of such programs must maintain continuity or interconvertibility of methods, as well as key sites and sampling times, to build on the large investments of the past while expanding services to scientists from a variety of disciplines.
A second part of the research explored the utility of and, in some cases, extended recently developed techniques for data visualization and analysis. Major emphases have been the development and application of principal component methods to time series ("modal" time series analysis), the use of generalized additive modeling in the service of model specification, and the use of bootstrap techniques to calibrate and estimate prediction error in statistical models.
Finally, these data sets and tools were used to investigate the variability in these systems. We are in the "natural history" stage of understanding ecosystem variability, in the sense that we still need to document laboriously the sources of interannual variability. Fortunately, although a variety of mechanisms potentially underlie interannual variability, few are actually important in any given data set, a phenomenon called modal dominance. Modal dominance implies that we can uncover most sources of variability in even the relatively short instrumental series (20 to 30 years) now available from long-term monitoring sites. We characterized the main sources of variability in primary production and other water quality features in the systems under investigation, leading to practical conclusions with management consequences.
The following activities were accomplished:
• We developed guidelines for optimizing sampling along the axis of an estuary. The high spatial variability of estuaries poses a challenge for characterizing estuarine water quality. We developed a rational way to choose interstation distance based on historical data and theoretical considerations, and showed that the bay was being sampled at an unnecessarily high frequency. This finding will influence the way in which other researchers carry out future sampling in the bay.
• We showed that flow is a major determinant of population abundance at all trophic levels in the San Francisco Estuary. Although the actual mechanisms are understood for only a few of these populations, the concept is now well accepted and these flow-abundance relationships have provided much of the scientific basis for restoring higher flows to protect estuarine populations.
• The position of .2 percent bottom salinity (denoted by X2) is a practical habitat indicator for the San Francisco Estuary. X2 has simple and significant statistical relationships with annual measures of many estuarine resources. X2 also satisfies other recognized requirements for a habitat indicator, and can be measured with greater accuracy and precision than alternative habitat indicators such as net freshwater inflow into the estuary. It now serves as a basis for setting water quality standards.
• A method was developed for analyzing long-term time series with a seasonal and spatial component. We developed a unique application of principal component analysis to decompose a seasonal time series for multiple stations into a simpler set of annualized and regionalized time series. This method has proved useful in uncovering long-term variability mechanisms in a variety of aquatic ecosystems.
• Phytoplankton production is the main primary food source for metazoan organisms on a delta-wide basis. This finding, established from historical data, field bioassays, and laboratory feeding experiments, was an important step in the reemergence of an estuarine paradigm in which detritus fuels ecosystem metabolism, but phytoplankton fuels the food web. A separate implication is that the removal of total organic carbon in agricultural drainage to prevent disinfection byproduct formation in drinking water is not a threat to the food supply for estuarine consumers.
• Long-term change in delta phytoplankton production is because of an exotic clam invasion and dam construction, whereas interannual variability is primarily climate related (i.e., flow related). We documented a halving of delta-wide production in the 1980s, thereby identifying a mechanism for the decline of at least some fish populations. The role of dams also is particularly interesting because it shows how planned dam removals will have large effects on estuarine production through transparency changes.
• Atmospheric deposition is a major source of nitrogen and significant source of phosphorous for Lake Tahoe. We were among the first to document clearly the role of atmospheric deposition in lake nutrient budgets and eutrophication, a concept that since has been widely verified. This finding has helped watershed managers develop appropriate nutrient control strategies.
• We determined the mechanisms underlying long-term variability in Lake Tahoe transparency. These studies clearly showed the existence of separate summer and winter modes and the reasons for them¾an essential step in the restoration program for the lake. We demonstrated that the loading of mineral suspensoids, in addition to nutrients, plays an important role in the water clarity decline. Current erosion control practices are not necessarily removing the right fraction of mineral particles; the clay-sized particles that do not settle out, but are the strongest light scatters. Our research project will potentially make erosion control practices more effective.
• Recent increases in Lake Tahoe transparency (since 1999) are the result of interannual climate variability, not an improvement in the underlying conditions of lake water. Our recent model for interannual variability finally enables managers to distinguish long-term from short-term change at the lake, and to get faster feedback on lake-wide responses to conservation programs.
• We have helped improve environmental monitoring programs for the San Francisco Bay-Delta and Lake Tahoe. Support from this grant enabled close cooperation with the agencies responsible for these monitoring programs, and for studies in the Stockton Deep Water Ship Channel, to review and improve the operation of these programs. These efforts included the 5-year review of the IEP program, as well as several reviews of ongoing total maximum daily load studies for the Ship Channel.
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, computing technology, Biochemistry, Environmental Microbiology, Fate & Transport, Watersheds, Monitoring/Modeling, Ecology and Ecosystems, water quality, ecological impact, contaminant transport models, computer simulation modeling, aquatic, fate and transport, watershed management, watershed restoration, database, computer science, data management, decision support systems, ecological research, ecology assessment models, aquatic modeling, alternative mechanistic models, hydrological transport model, analytical models, material transport, GIS, ambient particle properties, aquatic ecosystems, data analysis, ecosystem assessment, environmental stress, sediment transport, watershed sustainablility, hydrology, modeling, watershed influences, restoration strategies, ecosystem stress, ecological models, biodiversity, habitat, integrated watershed model
Relevant Websites:
Progress and Final Reports:
1999 Progress Report
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