Spatial and Temporal Trends in Water Quality

EPA Grant Number: R825433C057
Subproject: 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: Packard, Benjamin H
Project Period: October 1, 1996 through September 30, 2000
RFA: Exploratory Environmental Research Centers (1992) RFA Text |  Recipients Lists
Research Category: Center for Ecological Health Research , Targeted Research


This project seeks to develop methods for analyzing and displaying water quality data and investigate historical water quality databases to uncover mechanisms of spatial and temporal variability.


The investigators have completed an analysis of primary food resources for the Delta. The basic finding is that the Delta's food web is driven by phytoplankton production, despite the plentiful supply of other organic materials. The conclusion is based on estimates of the bulk organic matter supply from different sources, losses of dissolved organic matter during conversion to particulate matter, and the nutritional value of different particles. Investigators also examined quantitatively how different restoration strategies for the Delta-including an isolated conveyance facility, increased use of floodplains, flow and fish barriers, and increased shallow-water habitat-would affect phytoplankton production.

The second phase of this work is also near completion. Given the importance of phytoplankton production, investigators focused analysis on long-term changes in production and the mechanisms underlying these changes. Using techniques of time series analysis developed previously under CEHR sponsorship, they isolated two underlying mechanisms of variability in the Delta-wide primary production series. The first, operating in winter months, simply reflects the amount of river inflow. The mechanism is hydraulic residence time, which determines the amount of time phytoplankton has in the estuary to take advantage of the plentiful supply of nutrients. Effects of flow on water clarity could also play some role. The second mechanism operates in summer-fall. The main feature is a large drop in production after 1986, which probably represents the impact of an invasive clam on phytoplankton populations. This effect extends upstream of the clam's actual habitat and is probably due to transport effects that we are now investigating further. These two mechanisms, however, account for only about half of the overall variability. The remaining mechanisms appear to be local in their effects, and they do not have an identifiable signal in the Delta-wide production time series. They are now examining phytoplankton production and biomass at individual series to uncover these remaining mechanisms. On the San Joaquin R. at the upstream Delta boundary, for example, the control appears to be almost entirely hydrological, including river flow, agricultural return flows, and reservoir releases on the Stanislaus R. A statistical model describes the variability very precisely, including the large interannual variability in spring bloom size.

Expected Results:

Because the Delta has plenty of nutrients, growth rates of phytoplankton are essentially light-limited by the turbid waters. The increase in water clarity has been remarkable over the past 30 years, with the median value of total suspended solids in the Delta decreasing from about 30 to about 15 mg/L. This increase must have ameliorated the drop in phytoplankton production to a great extent. The optical quality of the Delta has been almost completely neglected, and yet it is central to understanding changes in primary production. Investigators expect to apply the approach used at Tahoe to a physical-based model of optical properties in the Delta. Specifically, they plan to apply the model that relates the inherent and apparent optical properties of a water body to its dissolved and particulate constituents, including composition (phytoplankton, mineral suspensoids, dissolved matter) and size spectra. They have all the tools and theory in place from the Tahoe work and have started some initial Delta analyses by using samples from our current CALFED project. They expect to lay the foundation for (1) understanding past changes in clarity; (2) giving modelers a "clarity module" for predicting future changes in clarity from the behavior of particles; and (3) developing a remote sensing capability for the Delta.

Supplemental Keywords:

Aquatic ecosystem, California, computer science, water quality, ecosystem assessment, phytoplankton, nutrients, ecosystem modeling., RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Waste, Water, ECOSYSTEMS, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, Water & Watershed, Restoration, Aquatic Ecosystem, Fate & Transport, Monitoring/Modeling, Environmental Microbiology, computing technology, Biochemistry, Terrestrial Ecosystems, Ecology and Ecosystems, Aquatic Ecosystem Restoration, Watersheds, fate and transport, aquatic modeling, habitat, aquatic, watershed management, ambient particle properties, decision support systems, alternative mechanistic models, biodiversity, ecosystem assessment, sediment transport, computer science, hydrological transport model, restoration strategies, modeling, watershed influences, hydrology, computer simulation modeling, data management, integrated watershed model, aquatic ecosystems, environmental stress, watershed sustainablility, data analysis, GIS, material transport, water quality, ecosystem stress, ecology assessment models, ecological impact, ecological models, transport modeling, analytical models, ecological research, watershed restoration, database

Progress and Final Reports:

  • 1997
  • 1998
  • 1999 Progress Report
  • Final 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