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1998 Progress Report: An Integrated Watershed Approach to Evaluate and Model Ecosystem Effects of Erosion and Pollutant Transport in Urbanized Subalpine Landscapes

EPA Grant Number: R826282
Title: An Integrated Watershed Approach to Evaluate and Model Ecosystem Effects of Erosion and Pollutant Transport in Urbanized Subalpine Landscapes
Investigators: Goldman, Charles R. , Jassby, Alan D. , Kavvas, M. Levant , Reuter, John E. , Schladow, S. G.
Current Investigators: Goldman, Charles R. , Heyvaert , Alan C. , Jassby, Alan D. , Kavvas, M. Levant , Reuter, John E. , Schladow, S. G.
Institution: University of California - Davis
EPA Project Officer: Perovich, Gina
Project Period: June 1, 1998 through May 31, 2001 (Extended to January 31, 2002)
Project Period Covered by this Report: June 1, 1998 through May 31, 1999
Project Amount: $879,376
RFA: Water and Watersheds (1997)
Research Category: Water and Watersheds

Description:

Objective:

This proposal integrates the fields of biological and ecological research, hydrologic, geochemical and engineering, social science research, and environmental modeling in a multi-disciplinary program designed to provide watershed managers and decisionmakers with a science-based understanding, and innovative tools for, the development of environmental policy. The specific objectives of this research to be conducted in the Sierra Nevada at Lake Tahoe include: 1) apply new hydrologic model to describe dynamics of non-point source pollutants over complex landscapes; 2) use lake modeling techniques and field measurements to quantify the fate of biogenic and inorganic particulate matter in Lake Tahoe; 3) integrate watershed processes related to erosion and pollutant transport with lake and stream response; 4) employ paleolimnological techniques to reconstruct lake and watershed response to historical disturbance; and 5) work within the context of existing agency and non-profit conservation groups to develop a watershed-scale erosion control management plan.

Progress Summary:

  • Development of Hydrologic Model - During the last year, the hillslope-scale component hydrologic process models were combined into one computer program to form a watershed hydrology model for the complex, mountainous landscape at Lake Tahoe. With its parameters estimated directly from the Ward Creek watershed's physical data, the newly developed hydrology model was then applied for validation purposes to the simulation of three consecutive rainfall-runoff events which occurred in the Ward Creek watershed during one week in the beginning of September 1998. Water table heights, which were observed one week prior to the rainfall-runoff events, were utilized as the initial condition for the simulation runs. The model simulation results, when compared to runoff observations at Ward Creek watershed, were quite satisfactory. The validation runs of the hydrology model are encouraging as the project team moves toward the development of erosion and sediment transport models at the next stage of the project.

  • Fate of Nutrient and Sediment Particulate Matter in Lake Tahoe's Water Column - Meteorological data are an essential component of our process driven hydrodynamic model; however, the lack of this type of data necessitated the installation of a meteorological station in Tahoe City. Lake hydrodynamics were directly investigated using data from three thermistor chains deployed in Lake Tahoe. Power spectrum analysis indicates strong oscillations with periods of approximately 14.3 hours, corresponding to the internal east/west seiching period. An intense internal wave climate was clearly evident. As surface upwelling was much stronger at the Index Station, the primary seiching direction is on the east-west axis. At the Index Station, two very strong wind driven seiches caused excursions of nearly 200 m and upwelling of hypolimnetic water to the surface. Particle size distribution has been attempted for both the streams flowing into Lake Tahoe and for the lake itself. The available size range was 2 to 100 microns, however particles larger than 10 microns were almost never detected. In the lower size ranges, the particle concentrations showed the expected log normal distributions, with increasing particle numbers with decreasing size. By far the greatest success has been achieved using the PMS Analysis System. The instrument has a limited size range up to only 20 microns, but as it can measure particles as small as 0.5 microns, it has significantly extended our capacity in the size range where light scattering is at a maximum. The accurate specification of nutrient loss coefficients is an essential step in the application of mass balance models to improve our understanding of a system and its response to mitigation. Sedimentary losses are of paramount importance in Lake Tahoe because long (650 year) hydraulic residence time. As part of the progress to date, we have measured nutrient settling velocities (vS) for phosphorus from the accumulation rates in several mid-lake sediment traps. The long-term average was found to be 16.4 m y-1 for phosphorus and 12.0 m y-1 for nitrogen. The response time of Lake Tahoe to reach final steady-state following P loading reductions was calculated to be on the order of 40-65 years. A similar, decadal scale, response was found for nitrogen. These values are essential input parameters to future modeling efforts on lake response to restoration. Calculations of N and P loading needed to balance these losses was very similar to estimates of nutrient loading to the lake.

  • Integration of Watershed Processes into Lake and Stream Response - A rigorous analysis of the 30+ year data base for Lake Tahoe, Secchi depth clarity was undertaken. A decadal trend exists (-0.25 m/yr), resulting from accumulation of materials in the water column. Based on available measurements, both phytoplankton-derived materials and mineral suspensoids may play significant roles in this trend. The mean seasonal pattern over the period of record was bimodal, with a strong annual minimum Secchi depth in approximately June and a weaker local minimum in December. The June minimum was considered to be due to the cumulative discharge of suspended sediment following melting of the seasonal snowpack. This view was found to be consistent with the measured seasonal pattern of suspended sediment discharge and with visual observations of sediment plumes entering the lake. The December minimum was attributed to the deepening of the mixed layer as the thermocline erodes at that time of year and passes through layers of phytoplankton and other light-attenuating particles which reach a maximum below the summer mixed layer, e.g. the deep chlorophyll maximum which is found below 50-60 m in Lake Tahoe. Based on sediment trap data for Lake Tahoe, we hypothesize that it is the combination of phytoplankton and inorganic particulate matter which accumulate at intermediate depths which is mixed into the surface waters and result in the December minimum in clarity. For large lakes such as Tahoe, management strategies for increasing outputs is not feasible and for all practical purposes impossible. A nutrient budget is first needed to allow us to identify the most important sources of loading. At this time five major sources of nutrients to Lake Tahoe have been identified: (1) direct atmospheric deposition and precipitation, (2) stream discharge, (3) overland runoff directly to lake, (4) groundwater and (5) shoreline erosion. During this past year, these were quantified using the extensive, long-term data base. For total phosphorus, the following contributions were estimated and listed by order of importance: direct runoff (15.5 metric tons, MT); stream loading (13.3 MT), atmospheric deposition (12.4 MT); groundwater (4 MT); and shoreline erosion (<0.5 MT). For total nitrogen the contribution by atmospheric deposition was >50% (233.9 MT), followed by stream loading (81.6 MT), groundwater (60 MT), direct runoff (41.8 MT) and shoreline erosion (<1 MT).

  • Reconstruction of Historical Watershed Events and Lake Response - Sediment core analyses allow us to examine ecosystem processes at a longer and more relevant time scale than can usually be attained from any existing monitoring data base; this improves our efforts to forecast ecosystem response to contemporary watershed disturbance. Based on the 210Pb results of five sediment cores from Lake Tahoe, the average mass sedimentation rate during the Comstock logging era (1860-1900) was 0.043?0.011 g cm-2 y-1. By comparison, the average mass sedimentation rate for the recent period (1970-1990) was 0.027? 0.006 g cm-2 y-1. Both these rates are significantly higher than the average sedimentation rate of 0.009 ?0.004 g cm-2 y-1 that was determined for the intervening period (1900-1970). Pre-disturbance sedimentation rates averaged 0.006 g cm-2 y-1, which is just slightly less the period 1900-1970. It appears that landscape recovery was rapid after clear-cut logging ended.

    • Future Activities:

    1) Application of new watershed hydrology model to the entire Ward Creek watershed using event-based, monthly and annual stream discharge as a calibration data set; 2) application of hydrology to the intervening zones where flow is discharged directly to the lake; 3) begin creation of sediment transport component of model; 4) quantify relationship between phytoplankton derived particulate matter and mineral suspensoids (combined as SPM), and Secchi depth using field data for chlorophyll, total suspended solids, Secchi depth, phytoplankton species counts and particle size analysis; 5) begin lake response modeling based on mass balance considerations for algal and non-algal SPM; 6) conduct lab and field tests to determine how the optical properties of SPM is affected by particle-size and how these properties translate into a change in clarity; 7) continue modeling of water column distribution of SPM with an emphasis on particle-size distribution; 8) continue measurements of urban runoff water quality and begin identification of specific areas of accelerated loading; 9) work with US Geological Survey and use the existing long-term stream water quality data base to determine land use - loading relationships; and 10) investigate the contribution of stream bank erosion as a sediment source to Lake Tahoe. These will all be done within the existing framework for monitoring and research which is currently being formalized by state, federal and local agencies and governments in the Tahoe Basin.


    Journal Articles on this Report: 8 Displayed | Download in RIS Format

    Other project views: All 56 publications 26 publications in selected types All 20 journal articles

    Type Citation Project Document Sources
    Journal Article Dogrul E, Kavvas ML, Chen ZQ. Prediction of subsurface stormflow in heterogeneous sloping aquifers. Journal of Hydrologic Engineering 1998;3(4):258-267. R826282 (1998)
    R826282 (2000)
    R826282 (Final)
    		 not available
    Journal Article Goldman CR. Four decades of change in two subalpine lakes. Baldi Lecture. Verhandlungen IVL 2000;27(Pt 1):7-26 R826282 (1998)
    R826282 (1999)
    R826282 (2000)
    R826282 (Final)
    		 not available
    Journal Article Goldman CR. Management-driven limnological research. Archives of Hydrobiology, Special Issues Advanced Limnology 2000;55:257-269. R826282 (1998)
    R826282 (1999)
    R826282 (2000)
    R826282 (Final)
    		 not available
    Journal Article Huovinen PS, Goldman CR. Inhibition of phytoplankton production by UV-B radiation in clear subalpine Lake Tahoe, California-Nevada. Verhundlungen der Internationale Vereinigung Limnologie 2000;27(Part 1):157-160. R826282 (1998)
    R826282 (1999)
    R826282 (2000)
    R826282 (Final)
    		 not available
    Journal Article Jassby AD, Goldman CR, Reuter JE, Richards RC. Origins and scale dependence of temporal variability in the transparency of Lake Tahoe, California-Nevada. Limnology and Oceanography 1999;44(2):282-294. R826282 (1998)
    R826282 (1999)
    R826282 (2000)
    R826282 (Final)
    R825433 (Final)
    		 not available
    Journal Article Kavvas ML, Chen ZQ, Tan L, Soong ST, Terakawa A, Yoshitani J, Fukami K. A regional-scale land surface parameterization based on areally-averaged hydrological conservation equations. Hydrological Sciences Journal 1998;43(4):611-631. R826282 (1998)
    R826282 (2000)
    R826282 (Final)
    R825433 (Final)
    		 not available
    Journal Article Reuter JE, Allen BC, Richards RC, Pankow JF, Goldman CR, Scholl RL, Seyfried JS. Concentrations, sources, and fate of the gasoline oxygenate methyl tert-butyl ether (MTBE) in a multiple-use lake. Environmental Science and Technology 1998;32(23):3666-3672. R826282 (1998)
    R825433 (Final)
    		 not available
    Journal Article Tayfur G, Kavvas ML. Areally-averaged overland flow equations at hillslope scale. Hydrological Sciences Journal 1998;43(3):361-378. R826282 (1998)
    R826282 (Final)
    R825433 (Final)
    		 not available
    Supplemental Keywords:

    Limnology, paleolimnology, watershed management, adaptive management, best management practices, ecological restoration, eutrophication, watershed disturbance, urbanization, subalpine, erosion, primary productivity, lake hydrodynamics, algal bioassays, runoff. , Ecosystem Protection/Environmental Exposure & Risk, Water, Geographic Area, Scientific Discipline, RFA, Ecosystem/Assessment/Indicators, Water & Watershed, Nutrients, Hydrology, Watersheds, Environmental Chemistry, Ecological Effects - Environmental Exposure & Risk, Ecosystem Protection, Ecology and Ecosystems, State, phytoplankton dynamics, water quality, hydrological stability, ecosystem effects, ecological response, fate and transport, watershed management, ecosystem indicators, limnology, biological integrity, sediment runoff, lake ecosystems, land use, urban landscapes, environmental monitoring, ecological exposure, aquatic ecosystems, erosion, nutrient transport, biogeochemistry, Nevada (NV), ecosystem, nutrient supply, suspended particulate matter, ecological models, ecological effects, pollutant transport
    Relevant Websites:

    http://trg.ucdavis.edu exit EPA
    http://www.engr.ucdavis.edu/~edllab/index.html exit EPA
    http://wwwnv.usgs.gov exit EPA

    Progress and Final Reports:
    Original Abstract
    1999 Progress Report
    2000 Progress Report
    Final Report

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    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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