Grantee Research Project Results
1999 Progress Report: An Integrated Watershed Approach to Evaluate and Model Ecosystem Effects of Erosion and Pollutant Transport in Urbanized Subalpine Landscapes
EPA Grant Number: R826282Title: 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. , Reuter, John E. , Schladow, S. G. , Kavvas, M. Levant
Current Investigators: Goldman, Charles R. , Heyvaert , Alan C. , Jassby, Alan D. , Reuter, John E. , Schladow, S. G. , Kavvas, M. Levant
Institution: University of California - Davis
EPA Project Officer: Packard, Benjamin H
Project Period: June 1, 1998 through May 31, 2001 (Extended to January 31, 2002)
Project Period Covered by this Report: June 1, 1999 through May 31, 2000
Project Amount: $879,376
RFA: Water and Watersheds Research (1997) RFA Text | Recipients Lists
Research Category: Water , Watersheds
Objective:
This project 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 decision makers 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 a 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 nonprofit conservation groups to develop a watershed-scale erosion control management plan.
Progress Summary:
A critical component for long-term planning at Lake Tahoe is a water clarity model, based on the lake's capacity to receive and process sediment and nutrients. By knowing the level of loading required to attain the desired lake conditions (TMDL approach), responsible agencies will be better able to plan in a more quantitative and progressive manner. Based on research from Years 1 and 2, along with our other extensive research and monitoring data base, we have been developing such a predictive model as the focal point of this Water and Watersheds Grant. The clarity model also provides the structure for future water quality research and monitoring in the Tahoe basin. The model will be used in a predictive fashion allowing agencies to assess lake response based on various levels and stages of watershed management. Information obtained with this grant was originally to serve as the building blocks to construct the clarity model. However, because of the pressing need for this type of management tool at Lake Tahoe, we are hoping to end this grant with a "first-generation" version of a clarity model. Ultimately, the clarity model should be able to identify the total amount of nutrient loading per year required to achieve the Secchi depth threshold. Coupled with a nutrient budget, regulators would then establish targets for reduction (i.e., expectation of a TMDL program). Planning documents, proposed projects, BMPs, and restoration/erosion control work could then be assessed on the basis of their ability to meet these target loads.
During this past year (Year 2), the following specific accomplishments were made towards construction of both a clarity model and a watershed sediment transport model:
Sediment Transport Model
During the last project year, the following research was accomplished: (1) the watershed hydrology model, that was developed and calibrated for Ward Creek Watershed during the 1998 project year, was validated by means of historical rainfall-runoff data; (2) the computer code of the watershed hydrology model, which was originally developed specifically for Ward Creek watershed, was completely rewritten and was generalized so that it can be used in any watershed; (3) a snowmelt component for the model was developed, its computer program was written, and it is being incorporated into the watershed hydrology model; (4) a two-dimensional channel flow routing algorithm was developed and its numerical computer code was written to model the in-stream erosion at Lake Tahoe watersheds effectively; this algorithm is currently being tested; (5) development of an overland rill-interrill area erosion model was started and is continuing; (6) the developed watershed hydrology model was applied to Ward Creek watershed to assess the impact of various fire scenarios on the water balances of the basin; and (7) field work on the observation of both surface and subsurface flow, snowmelt, and sediment/nutrient transport processes continued.
An interesting application of this model within the Ward Creek watershed was made to investigate the impact of different fire scenarios. The main objective of this study was to test the model's utility as an environmental risk-assessing tool. The use of prescribed burning as a forest health management tool is being considered at Lake Tahoe to avoid a catastrophic wildfire, which is a major priority in the Tahoe basin. However, modeling efforts to quantify the change of hydrology due to fire are not common. From our preliminary work, it was concluded that forest fires will have a minimal effect on land surface erosion and landslides over the Lake Tahoe watersheds for the short term of less than one year. However, forest fires may have significant adverse effect on land surface erosion and landslides on the long term, within several years after the occurrence of fires, especially under critically-intense rainstorms. To assess such long-term effects it is necessary to perform long-term simulations of hydrologic and erosion/sediment transport processes over the Lake Tahoe watersheds under the various fire scenarios.
Water Clarity Model
Progress on the construction of a numerical model to describe the changes in Lake Tahoe water clarity has occurred in the area of data collection and collation of the model input files. Data are necessary for the development, forcing, and verification of the lake model and consist of: (a) meteorological data for driving the hydrodynamic submodel and water quality data for driving the water quality submodel; (b) temperature data from thermistor chains at two sites within the lake, and surface temperatures from surface thermistors on four rafts for understanding of lake hydrodynamics, and the initialization and validation of the model; (c) stream temperature and sediment data to understand inflow insertion dynamics; and (d) particle size distribution data in both the lake and the inflowing streams.
Throughout 1999, water samples were collected at two sites in Lake Tahoe and eight of the tributary streams. Lake Tahoe samples were collected at 10-20 different depths at the MID lake station from the surface to 450 m, and from 13 different depths at the INDEX station from the surface to 105 m. Water samples were analyzed using a LIQUILAZ-SO2 particle counter, which measured both particle number concentration and particle size distribution in the range of 0.5 µm to 20 µm. In addition, starting in September 1999, lake samples at both the MID and INDEX stations have been routinely analyzed by Scanning Electron Microscopy coupled with x-ray analysis. By measuring x-ray spectrums from individual particles, it was possible to classify size-specific particles as either organic or inorganic for use in the optical submodel.
For lake samples, it was found that particle number concentration reflected seasonal changes in the lake. Lake Tahoe typically is the clearest in February due to negligible runoff and low biological activity, and the least transparent in June, typically due to the influx of suspended sediment from the melting of the snowpack. As stream flow decreases and particles settle out of the water column, the lake water becomes progressively clearer throughout the summer. Particle size analysis of lake water samples have shown conclusively that the great majority of particles are very small. By number, 99 percent of the particles are less than or equal to 5 µm in spherically-equivalent diameter. Fractions of inorganic versus organic particles for the INDEX station range from a high of 71 percent organic and 29 percent inorganic in mid-November to 46 percent organic and 54 percent in late-February. Typically, the fraction of organic particles was higher than inorganic. However, based on Jassby, et al. 1999, we expect the inorganic particles to dominate in May-June as snowmelt delivers eroded soil from the watershed.
At this stage, the model optical submodel includes all major water constituents needed to support a predictive model of water clarity. While the optical submodel is now constructed, calibration and verification of the model are under way. Using realistic values for lake particle distribution and concentration, size categories and composition, predicted results for Secchi depth from the submodel agree well with observed Secchi. For example, for conditions with 0.30 mg/l of suspended solids consisting of 90 percent organic and 10 percent inorganic particles, the predicted Secchi depth of 17 m was similar to the observed Secchi depths between 15 and 20 m (for different dates). The model also indicates that a small concentration of very fine sediment has a large effect on clarity, and that a shift from larger to smaller particles of the same total mass causes a reduction in clarity, as expected.
Future Activities:
During the third year, the following work is being planned to complete the hydrology/sediment transport model: (1) the watershed hydrology model, with its newly developed snowmelt and 2-D stream flow routing components, will be applied to some historical snowmelt-runoff events at Lake Tahoe to validate the model for the snowmelt-induced runoff events; (2) the development of the overland rill flow-sheet flow erosion/sediment transport/ nutrient transport model will be completed and its computer code will be written; (3) the overland erosion/sediment transport/nutrient transport model will then be incorporated into the watershed hydrology model, and will be applied to some historical events over Ward Creek Watershed for its calibration and validation; and (4) the field observation of flow/sediment transport processes will be continued to achieve a better understanding of these processes. The clarity model consists of three major components: (1) a hydrodynamic component that encompasses the physical processes of mixing, sediment suspension, and particle settling; (2) a water quality component that reflects biochemical processes such as nutrient uptake and cycling, algae growth and zooplankton dynamics, and dissolved oxygen cycling; and (3) an optical component that derives Secchi depth and other optical parameters from absorption and scattering characteristics based on dissolved and particulate matter predictions from the other model components. Components 1 and 3 are virtually ready for incorporation into the final clarity model. Component 2 is being conducted in collaboration with Xavier Casamitjana and Joaquim Losada from the University of Girona, Spain, and will be accomplished by the end of the year. Our final action will be to combine these three components into a single, predictive clarity model. This is expected to begin this summer and a "first-generation" model will, hopefully, be completed by the grant's end.
Journal Articles on this Report : 7 Displayed | Download in RIS Format
Other project views: | All 57 publications | 21 publications in selected types | All 15 journal articles |
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Goldman CR. Four decades of change in two subalpine lakes--Baldi Lecture. Verhandlungen der Internationalen Vereinigung Limnologie 2000;27(Pt 1):7-26. |
R826282 (1998) R826282 (1999) R826282 (2000) R826282 (Final) |
not available |
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Hatch LK, Reuter JE, Goldman CR. Daily phosphorus variation in a mountain stream. Water Resources Research 1999;35(12):3783-3791. |
R826282 (1999) R826282 (2000) R826282 (Final) R825433 (Final) |
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Hatch LK, Reuter JE, Goldman CR. Relative importance of stream-borne particulate and dissolved phosphorus fractions to Lake Tahoe phytoplankton. Canadian Journal of Fisheries and Aquatic Sciences 1999;56(12):2331-2339. |
R826282 (1999) R826282 (2000) R826282 (Final) R825433 (Final) |
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Heyvaert AC, Reuter JE, Slotton DG, Goldman CR. Paleolimnological reconstruction of historical atmospheric lead and mercury deposition at Lake Tahoe, California-Nevada. Environmental Science & Technology 2000;34(17):3588-3597. |
R826282 (1999) R826282 (2000) R826282 (Final) R825433 (Final) |
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Huovinen PS, Goldman CR. Inhibition of phytoplankton production by UV-B radiation in clear subalpine Lake Tahoe, California-Nevada. Verhandlungen der Internationalen Vereinigung Limnologie 2000;27(Pt 1):157-160. |
R826282 (1998) R826282 (1999) R826282 (2000) R826282 (Final) |
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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) |
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Jassby AD, Goldman CR, Reuter JE, Richards RC. Biostatistical evaluation of long-term lake clarity record. Verhandlungen der Internationalen Vereinigung Limnologie 2000;27:2634-2635. |
R826282 (1999) R826282 (2000) R826282 (Final) R825433 (Final) |
not available |
Supplemental Keywords:
limnology, water clarity, watershed management, adaptive management, best management practices, ecological restoration, eutrophication, watershed disturbance, urbanization, subalpine, lake hydrodynamics, erosion, runoff, modeling., RFA, Scientific Discipline, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Nutrients, Hydrology, Water & Watershed, Environmental Chemistry, Ecosystem/Assessment/Indicators, Ecosystem Protection, State, Ecological Effects - Environmental Exposure & Risk, Ecology and Ecosystems, Watersheds, limnology, environmental monitoring, fate and transport, hydrological stability, nutrient supply, nutrient transport, ecological effects, ecological exposure, erosion, watershed management, urban landscapes, pollutant transport, ecosystem effects, subalpine landscapes, biological integrity, phytoplankton dynamics, Nevada (NV), ecosystem indicators, sediment runoff, aquatic ecosystems, ecosystem, water quality, biogeochemistry, ecological models, land use, lake ecosystems, suspended particulate matterRelevant Websites:
http://trg.ucdavis.edu Exit
http://www.engr.ucdavis.edu/~edllab/index.html
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http://wwwnv.usgs.gov Exit
Progress and Final Reports:
Original AbstractThe 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.