Grantee Research Project Results
1999 Progress Report: Integrated Urban Watershed Analysis: The Los Angeles Basin and Coastal Environment
EPA Grant Number: R825381Title: Integrated Urban Watershed Analysis: The Los Angeles Basin and Coastal Environment
Investigators: Turco, Richard , Fong, Peggy , Berk, Richard , Ambrose, Richard , Dracup, John A. , Forrester, Graham E , Fovell, Robert G , Venkatesan, M. Indira , Orme, Antony , MacDonald, Glen , Walter, Hartmut , Suffett, Irwin , McWilliams, James , Feddema, Johannes , Stolzenbach, Keith , Raphael, Marilyn , Stenstrom, Michael , Vance, Richard , Friedlander, Sheldon , Trimble, Stanley
Current Investigators: Turco, Richard , Friedlander, Sheldon , Berk, Richard , Ambrose, Richard , Fong, Peggy , Dracup, John A. , Feddema, Johannes , Forrester, Graham E , Fovell, Robert G , MacDonald, Glen , McWilliams, James , Orme, Antony , Raphael, Marilyn , Stenstrom, Michael , Stolzenbach, Keith , Suffett, Irwin , Vance, Richard , Venkatesan, M. Indira , Walter, Hartmut , Trimble, Stanley , Hamner, William M
Institution: University of California - Los Angeles
EPA Project Officer: Packard, Benjamin H
Project Period: December 1, 1996 through November 30, 1999 (Extended to November 30, 2000)
Project Period Covered by this Report: December 1, 1998 through November 30, 1999
Project Amount: $1,200,000
RFA: Water and Watersheds Research (1996) RFA Text | Recipients Lists
Research Category: Watersheds , Water
Objective:
This project seeks to understand the processes that control water availability and quality in a major urban watershed?Santa Monica Bay adjacent to the Los Angeles Basin in Southern California. The study is based on the coupling of data and models that bear on a wide range of factors that influence the water resource problem, including: regional meteorology and climatology; basin hydrology, vegetation and land use; anthropogenic water consumption and disposition; runoff sources of sediments, toxics, and nutrients; air pollutant transport, transformation, and surface deposition; downstream wetlands ecology and filtering; and coastal water circulation, biogeochemistry, and sediments. The various aspects of the problem are being addressed by members of the scientific team assembled through UCLA?s Institute of the Environment. The effort consists of a broad synthesis of observational data?in situ measurements, remotely sensed data, and local geographical information?and model simulations of material flow, deposition, transformation, and bioassimilation. Both the observational and computational data are being collected within a Geographical Information System (GIS) for analysis and applications. Models are being linked to provide an assessment of pollutant mass budgets in Santa Monica Bay, a primary coastal reservoir along the Los Angeles coastline. The assessment will treat sources of trace chemicals, deposited directly from the air, in runoff from land, and through outflows of wastewater. The dynamics and flushing of the embayment will be studied in the context of ocean circulation along the western coast, and the biogeochemical response of the bay will be evaluated in terms of pollutant fluxes.
Progress Summary:
During the past year, the various disciplinary components of the Watershed project were aggregated into four principal study areas that are more interdisciplinary in nature. These areas are further integrated in the context of a Santa Monica Bay mass budget analysis. Presently, the ?Air? component consists of regional meteorological and precipitation modeling and data analysis, air quality, and regional climatology, including studies of drought and wind. The expanded ?Land/Hydrology? component encompasses hydrological modeling (streams and rivers, streamflow, sediment), runoff chemical analysis, and GIS elements. The ?Wetlands? project seeks to characterize the flora and fauna of the urban salt marsh and estuarine environments, as well as the responses of organisms and ecosystems to various stresses induced by other components. The ?Ocean? component integrates coastal circulation with biogeochemical modeling and physical analysis of air-water-sediment transfer processes. Of all the components, Wetlands has remained relatively intact over the last few years, although interactions with Land/Hydrology have increased. The other three primary components represent the synthesis of a broader array of initial sub-projects that merged over time in a natural way. In the final year of the project, integration will be pursued at a higher level, in which the four aggregated components will be linked in an explicit manner to conduct a specific analysis of the pollutant mass balance for Santa Monica Bay.
In the following paragraphs, we first summarize recent progress in each of the primary components. A strategy to integrate these components is then discussed. Details concerning the research findings will appear in a series of published articles.
Air Component:
Mesoscale Modeling?The MM5 mesoscale dynamics model was applied to study rainfall events in the Los Angeles Basin. Calculated precipitation was compared to corresponding rain gauge and streamflow data available for Malibu and other watersheds. The MM5 was utilized with and without data assimilation (Four Dimensional Data Assimilation, or FDDA) to determine if the fidelity of the predictions could be improved. It was shown that FDDA increased the accuracy of the forecasts, although only marginally. Following this validation study, simulated precipitation rates and patterns were coupled to a hydrological code adopted for the Watershed analysis (see below). In a particular case of a hard rain event, the calculated and observed hydrographs were found to agree quite well. This investigation also demonstrated that meteorological predictions could lead to improved representation of streamflow, as compared to hydrographs generated using rain gauge data alone.
During the reporting period, steps were taken to extend the precipitation simulations to higher spatial resolution. In one approach, calculations conducted with the MM5 at very fine resolution were carefully compared to rain gauge and hydrologic data. In a second approach, a wavelet analysis technique was applied to extrapolate coarse resolution modeled rainfall patterns to much smaller spatial scales. Neither approach was completely satisfactory, despite the great additional cost of the calculations. At present, radar reflection measurements are being evaluated as a means of identifying geographically fixed relationships between topographical structure and precipitation features at various spatial scales to improve the wavelet approach.
Atmospheric Deposition?A field study was conducted to define the particulate contribution to the surface water chemistry in Santa Monica Bay. This work is closely related to the focus on the bay in the Ocean component of the Watershed project. Samplings of air and the surface microlayer (SMIC), as well as bulk water, were conducted along several transects of the bay. Size-resolved aerosol samples were analyzed for trace metal composition, and a source apportionment analysis was conducted. A novel feature of this work is the use of identical chemical analysis techniques for samples from all three media (air, SMIC, and water) to allow comparison of relative tracer abundances. Further, both inland and marine conditions were monitored to identify gradients in sources. The study included a diurnal characterization of the aerosol flux to the bay.
We note that tracer enrichments in the SMIC were greatest during the morning hours (2:00?10:00 a.m.). This corresponds closely with measured variations in the chemical composition of particles below 0.67 microns in (aerodynamic) diameter. Not all of the elements sampled followed this rule, however. For example, Mn and Cr showed a minimum in the ultrafine fraction during the night from 11:00 a.m.?5:00 p.m., while Ni, Cd, and Pb showed the opposite trend, exhibiting a maximum during the day and a minimum during the morning sampling period. Preliminary mass balance estimates of the atmospheric dry deposition rate to surface waters were made, and are reported elsewhere.
Air Quality Modeling?In support of the Santa Monica Bay deposition studies, a number of detailed simulations were conducted using the UCLA Surface Meteorology and Ozone Generation (SMOG) model. The conditions investigated included a series of common synoptic states associated with typical summer ?smog? days, and with ?Santa Ana? wind conditions, in which polluted air is forced out over the bay. The meteorological predictions were compared with MM5 high-resolution simulations, and with climatological wind data for Santa Ana conditions. Thus, the SMOG calculations could be reasonably constrained with respect to the dynamic variables.
The SMOG simulations revealed the significance of the synoptic state to the deposition of particles and gases over the bay. The deposition was enhanced by orders of magnitude during the day for Santa Ana conditions. Interestingly, a large diurnal variation was predicted for typical (non-Santa Ana) conditions as a result of land breezes that develop in the evening hours in the Los Angeles Basin, coupled with the reduced depth of the marine boundary layer owing to the more stable air layers over the cool expanse of coastal ocean. The geographical and temporal characteristics of the deposition also indicate heavy deposition near the headwaters of major drainages in the eastern and northern reaches of the basin. This inland deposition pattern is found to correlate with nitrate content measured in runoff from these areas. The present simulations represent the first quantitative estimates of regional scale deposition patterns of air pollutants such as nitrates in the Los Angeles Basin, and their potential to contribute to the runoff component to Santa Monica Bay and other coastal receptors. The patterns and variations, and especially the extremes, in air deposition rates predicted will be important in determining the total mass input from air pollution directly onto, and indirectly into, Santa Monica Bay.
Regional Climatology? Records of natural precipitation and drought variability within the Los Angeles Basin over a period of more than 1,000 years before the present have been constructed using tree ring measurements. The feasibility of deducing corresponding records of stream-flow for the major regional river systems also was assessed. Based on data collected under the Watershed project, the climate record has been fully reconstructed for Climatic Zone 6, which extends along the coastal region of Southern California from Santa Barbara to San Diego, and includes all of the drainages to Santa Monica Bay. Such a record is crucial in estimating the potential extremes of streamflow to the bay during periods of unusual rainfall. Hence, efforts to assess the transport and deposition of pollutants into Santa Monica Bay can be scaled against extreme events in the climatic record to define natural variability.
Tree ring sampling was completed at 10 sites selected for the Los Angeles Watershed project (having trees old enough for the present purposes). The data have been analyzed, crossdated, and archived for further use. Among the key results are the following:
Statistically verifiable models of winter precipitation and Palmer Drought Severity Index (PDSI) can be reconstructed for the last ~1,000 years for the Los Angeles basin.
Very severe droughts, with precipitation at least 2 standard deviations below the mean for the period 1895-2000 have occurred at least 14 times in the past 600 years. Droughts in which precipitation was at least 1 standard deviation below the 1895-2000 mean have occurred more than 100 times.
Although there is no significant trend in average precipitation over the past 600 years, there is evidence that periods of decadal to multidecadal dry phases are relatively common. The most recent of these occurred during the period 1950-1980.
In terms of long-term dry periods, the 20th Century appears relatively representative of the long-term variability in the Los Angeles climate system. It also appears that there have been years prior to the 20th Century that experienced greater droughts and heavier precipitation than appear in instrumental records.
Time series analysis of drought frequency and correlations with external forcing factors indicates that only about 30 percent of the variability in Los Angeles precipitation can be attributed to El Nino and La Nina events. The decadal-scale variations in dry and wet periods appear to be correlated with the Pacific Decadal Oscillation (PDO), which is a cycle of warming and cooling of sea surface temperatures off the Pacific Coast of North America.
The relationship between annual or monthly streamflow and tree ring width is statistically insignificant. Hence, streamflow in the basin appears to be controlled by individual storm events whose impacts are not captured by tree ring growth.
Land Hydrology Component:
Hydrological Modeling and Analysis?In the past year, the hydrological component of the project adopted a version of the TOP model for applications in several Los Angeles area watersheds. In the important Malibu Creek watershed, which is a major feed for Santa Monica Bay, detailed information on elevation, land use, vegetation type, and soils were collected from regional agencies and analyzed for accuracy. Other data were compiled for model calibration and validation studies, including streamflow and precipitation measurements. Initial validation runs were made for Malibu Creek. In parallel with the hydrological modeling, a historical frequency analysis was performed on the streamflow and precipitation data for the Malibu Creek watershed. The hydrological model was then run separately, and coupled to the regional meteorological model, described above, for comparison to the statistical results. In this case, the MM5 was used to generate high-resolution temporal and spatial distributions of precipitation to drive the TOP code. The performance of the coupled simulation system was found to be excellent under the circumstances investigated.
Several dynamic river models were investigated for their ability to predict time-dependent flow within the Los Angeles River system, the major drainage for much of the western and northern regions of the basin. The Los Angeles River feeds into San Pedro Bay just south of Santa Monica Bay, and currents often carry the output along the coast to the bay. Both the DWOPER (Dynamic Wave Operational Model), and FLDWAV model were considered, as they allow fundamental transient flow studies to be conducted, and are readily coupled to mesoscale meteorological models such as the MM5, and surface hydrological models such as TOP. Stream gauge and engineering data were collected for the purpose of testing the DWOPER code along a stretch of the Los Angeles River. With this model in place, the runoff into the San Pedro Bay can be quantified in conjunction with the meteorological forecasting system, and potential impacts of extreme rainfall conditions indicated by historical tree ring analysis can be assessed.
Chemical Runoff?The runoff element of the project collected a substantial new database on the trace composition of wetland and coastal waters, focusing on Santa Monica Bay. Local sources were calibrated in the framework of an existing runoff code calibrated using measurements of the composition of streams in the region, particularly those in heavily impacted urbanized watersheds like Ballona Creek. The runoff chemistry code is based on GIS and hydrological analysis techniques. Runoff materials?from lead and other metals, to nutrients, to grease and oil? also were measured directly in receptor waters for the first time. The data analysis, which has not yet been completed, connects chemical runoff measurements with air and surface microlayer data taken during the Watershed project. The runoff mass fluxes will be compared to predictions of air deposition rates determined under the air quality component of the project. Possible airborne contributions to runoff chemistry are being quantified for the first time as well using the air deposition predictions over land.
Geographical Information Systems?The development and application of GIS analysis to the Watershed project fits most comfortably in the Land/Hydrology component. The land-use and runoff elements of the Watershed project directly incorporate GIS applications. During the past year, a new GIS laboratory was established around the Watershed project utilizing equipment supplied by the Intel Corporation under a $750,000 grant for this purpose. The laboratory consists of three computer facilities (located in the Institute of the Environment, and the Departments of Geography and Atmospheric Sciences) connected by fiber optic cable. An advanced GIS/remote sensing analysis laboratory, which became operational last year, houses the Watershed databases, and soon will provide a home for a Watershed Web site (presently under construction). Another essential facility is the Regional Environmental Assessment Laboratory (REAL), which provides high-performance computing resources to Watershed modelers and data analysts. A closely connected top-end GIS teaching facility also is under development, in which Watershed research will be used as a pedagogical tool. The GIS and REAL laboratories currently offer access to watershed and related information for project researchers and students. Eventually, this information will be made public over the Internet through a dedicated Web site.
Wetlands Component: The Wetlands component has focused on the effects of pollutants on estuarine plant and animal species. The plant element of this research is examining the impacts of nutrient influx on the growth and population dynamics of algae and vascular vegetation in mudflats and marshes. The fish element is addressing the effects of heavy metal and organic pollutants on the growth rates and survival of estuarine fish. The wetland researchers have conducted extensive field studies under the Watershed project. Details of the experimental design and measurements are forthcoming in a series of papers. The team currently is considering the impacts of runoff and air deposition on wetlands, and the contribution of wetlands to coastal biogeochemistry.
Estuarine Plants?The plant research has focused on nutrient fluxes into and cycling within estuaries, and the effects of nutrient enrichment on intertidal and subtidal marine plants (algae and vascular plants). Because all of the original coastal marshes comprising the Santa Monica Bay watershed have effectively been destroyed by development or dredging, Upper Newport Bay (UNB) and Mugu Lagoon were used as prototypical study sites. Quarterly field sampling was conducted for 1 year in UNB to measure nutrient levels in the water column, sediments, and algal tissue at eight locations. In addition, the magnitude and species composition of algal blooms in the bay were measured. This data serves as a baseline for assessing the potential impacts of planned wastewater releases on algal blooms and the nutrient status of the bay. Similar analyses can be applied to the remnant Santa Monica Bay estuaries.
Recent field sampling indicates that Newport Bay is highly eutrophic, with water column nitrate levels in the upper bay reaching 800 µM, a level 100 times greater than ocean water. However, most of these nutrients are removed by macroalgae, or in sediments, as the water is transported through the estuarine system. Nitrogen levels in algal tissue reflect the enrichment. A distinct seasonal cycle also is found, in which the algal community shifts from dominance by benthic diatoms in winter, to blooms of Enteromorpha in spring and early summer, and finally a replacement of Enteromorpha by Ulva in late summer and early fall.
Observations taken quarterly provide conflicting indicators of nutrient limitation for the macroalgal blooms investigated. Water column N:P ratios were high?up to 370:1?suggesting potential phosphorus limitation. On the other hand, sediment N:P ratios were low?less than 4:1?suggesting nitrogen limitation. A microcosm experiment was conducted to test whether macroalgae were nitrogen or phosphorus limited in this system. The results indicate that even at high nutrient levels (300 µM N and 30 µM P) macroalgal growth was nitrogen limited. Despite high nitrogen loading over the course of the experiment, the burden in the water column remained low, being removed by the increasing algal biomass. The Watershed data indicate that macroalgae also employed N originating in sediments for growth. At the same time that nitrogen was accumulating in algal tissue, it was decreasing in microcosm sediments.
These results have important implications for the management of UNB. For example, it has been argued that winter releases of treated wastewater would not worsen algal blooms in the bay because macroalgae are not present during this season to utilize the enhanced nutrients. However, the present study has shown that this assumption is incorrect, and that macroalgae are capable of utilizing sediment nutrient reserves to fuel growth, which could occur in summer and fall following winter deposition.
The plant team undertook two other experimental studies. In one, the response of E. intestinalis to fluctuating salinity in a coastal estuary was measured to quantify the potential sensitivity to highly variable anthropogenic freshwater influxes. In a fully crossed two-factor experiment, E. intestinalis was subjected alternatively to fresh and ambient waters over 24-day periods. Depending on the nutrient base and duration of exposure to freshwater, significant effects were recorded. These included loss of pigmentation, decreased wet and dry biomass, increased wet-to-dry mass ratios, decreased removal of nitrogen and phosphorus from the water column, and an accumulation of NH4 in the water column. It was concluded that the growth of E. intestinalis is quite sensitive to reduced salinity and may suffer if it is regularly reduced.
Finally, the nitrogen dynamics of salt marsh vascular plants was studied. In a Southern California salt marsh subject to previous long-term eutrophic conditions, S. virginica (pickleweed) was found to respond strongly to applied nitrogen. Although phosphorus addition did not result in significant biomass changes, it did influence tissue nutrient levels. Again, such results have important implications for efforts to restore and protect wetlands from the consequences of human runoff.
Impacts of Pollutants on Estuarine Fish?Although a wide range of organic and inorganic pollutants are known to enter estuaries, little is known about their effects on resident fish populations. The present Watershed studies considered: how different concentrations of chemical pollutants might affect the abundance and population dynamics of wild estuarine fish; how prolonged exposure of caged fish to pollutants in situ influences their growth rates and survival; and how fish from different estuaries differ in their responses to pollution. These questions were investigated by taking surveys of fish populations and characteristics at the sites of interest, by conducting a number of specific caging experiments at these sites, and by the use of correlated laboratory experiments under well-defined conditions.
Fish surveys were conducted in five estuaries within the greater Los Angeles area: Alamitos Bay, Anaheim Bay, Ballona Wetland, Mugu Lagoon, Newport Bay. Individuals were counted, measured, and their ages and growth rates estimated (using growth rings in the otolith, or ear bone). At each site, samples of sediment and water also were collected and analyzed for metallic pollutants associated with the sediment, sorbed to suspended solids, or in the aqueous phase. A suite of organic pollutants was measured, including PCBs, DDTs, phthalates, phenols, pesticides, and PAHs, with the goal of correlating pollutant loadings with fish populations. Tissue samples also were analyzed for the presence of organic pollutants, and these values were correlated with concentrations in sediments.
Four caging experiments were conducted to determine fish survival and growth rates at different sites with varying pollutant loads. The California killifish (F. parvipennis), and the longjaw mudsucker (G. mirabilis), were each used in two experiments. Both species are common at all five estuaries surveyed, and are representative of the different life histories exhibited by estuarine fishes. The killifish is a mobile, mid-water species (and also is a member of the genus commonly used in toxicological studies), while the mudsucker is a site-attached benthic fish likely to be exposed to pollutants in sediments.
In the caging experiments, no consistent differences were detected in the growth rates among fish originating from various estuaries transplanted into a specific estuary. On the other hand, consistent differences were found in the growth rates of fish transplanted to a specific site, with fish transplanted to Ballona growing fastest (compared to fish transplanted to Mugu and Alamitos). Similarly, fish transplanted to Ballona survived in greater numbers than fish transplanted to the other estuaries.
To supplement the field experiments on killifish, a laboratory test was conducted to investigate the possibility that populations from different estuaries have evolved differences in inherent performance. Toward this end, fish were collected from each of three wetlands (Ballona, Mugu, and Alamitos) and placed in a series of aquaria (three aquaria per estuary). The fish were then maintained under constant conditions for 2.5 months while being fed ad libitum. Differences in growth should reflect inherent genetic differences among the populations. The results show that subtle differences in the growth rates of these specimens are indeed apparent, with fish from Ballona growing somewhat faster than those from other sites. However, the differences were not statistically significant.
Regarding the relationship of fish survival to pollutant exposure, initial studies centered on pollutants in sediments. Twenty-one metals and 142 organic compounds were screened in sediment samples from the study areas. When these chemicals are examined individually for correspondence with data on fish performance, a complex pattern emerges. For example, during the first field test on G. mirabilis, none of the metal concentrations at the sites varied in a manner that corresponded with the growth rate or survivability of the fish. Each metal varied more or less independently between estuaries. These results point to the difficulty in correlating any one, or even several, pollutant factors with observed ecological change. In the field, fish grew fastest at Ballona, at intermediate rates at Mugu, and slowest at Alamitos. The highest pollutant loadings also were found in Alamitos, which is in accord with the fish growth results. However, the lowest pollutant levels were found in Mugu, not Ballona.
The standard measures of pollution that were used in this preliminary assessment assume that the toxic effects of individual chemicals are additive in situations where organisms are exposed to multiple compounds. Results from the Watershed field experiments indicate that this assumption is incorrect, at least for the wetlands studied. New measures of combined pollutant toxicity are being explored to provide a more consistent explanation of the fish data.
Coastal Ocean Component:
Coastal Ocean Dynamics and Modeling?A new Regional Ocean Modeling System (ROMS) has been developed under the Watershed project. ROMS currently is being applied to study ocean circulation along the southern California coast and Santa Monica Bay. A novel numerical technique was implemented to allow nested simulations from Pacific Ocean basin gyres, to west coast currents, to eddies in Santa Monica Bay. This methodology leads to resolution that is sufficient for budget calculations in the bay, while still properly representing the dynamical forcing at larger scales. Model simulations were tested against measurements of ocean surface currents, sea surface temperatures, sea level height, and ocean color, with good results. Satellite data sets (including AVHRR, RADARSAT, and SeaWIFS) also were utilized to characterize eddy circulations in Santa Monica Bay, as a prelude to the validation of very high resolution simulations.
In the last year, a biogeochemical multitrophic-level nutrient-based model was introduced into ROMS. This coupled circulation/ecosystem model has been used to conduct preliminary studies of the dynamical character of the California Current System, its vigorous upwelling and mesoscale eddy variability, and the implications of such dynamics for phytoplankton populations. An important finding of this analysis is that the mean and seasonal coastal ocean currents, and the corresponding distributions of tracers and biological properties, are strongly altered by transient circulations and eddies. Although calibration of the ecosystem model has not yet been completed, preliminary comparisons between predicted and measured patterns of productivity in coastal upwelling zones are encouraging. Further, ROMS properly predicts the offshore magnitude and extent of these biologically active zones, while also resolving eddy-scale features in the distribution of biomass, as observed. It follows that ROMS should be more than adequate for simulating the circulation of Santa Monica Bay and other small coastal structures.
Santa Monica Bay Deposition Study?A number of measurements have been conducted on Santa Monica Bay under sponsorship of the Watershed project. These measurements include aerosol characterization (described under the Air component above), surface microlayer collection, and water column sampling, as well as high-resolution hydrographic surveys. The work has been conducted from the UCLA vessel, Sea World. The air, sea-surface, and water observations are designed to determine the contributions of airborne particulate matter to pollution in Santa Monica Bay. This project is leveraged by resources deployed by the Southern California Coastal Water Research Project, the Santa Monica Bay Restoration Project, and Department of Public Works of Los Angeles County. The basic airborne and surface layer results are summarized under the Air component above.
Data relevant to the surface/water aspects of the deposition study were collected during the reporting period. Unique measurements of the concentrations of inorganic and organic constituents in the microlayer and bulk water of Santa Monica Bay were obtained along transects across the bay, and over diurnal cycles. Microlayer concentrations under dry meteorological conditions provide an indication of the intensity of atmospheric deposition. Preliminary data indicate that the concentrations of specific target constituents are significantly enhanced in the microlayer compared to bulk water, and that the enhancement is greatest near shore and after a period of offshore winds. These findings implicate atmospheric deposition from the urban airshed as a significant source of contaminants in the Santa Monica Bay. The microlayer composition measurements currently are being correlated with the aerosol tracer data at the same times and places, both to determine the relative and absolute rates of deposition of various materials to the coastal waters, and to identify the principal factors that may control microlayer composition along the entire Los Angeles coastline.
Related to this study, the Institute of the Environment (IOE) hosted an U.S. Environmental Protection Agency-sponsored workshop in February 2000 on ?Where Air and Water Meet: Atmospheric Deposition to the Pacific Coast.? Experts from across the United States attended the workshop. A report is in preparation for the USEPA.
Coastal Sediment Chemistry?The Los Angles Watershed research agenda includes the systematic characterization of chemical tracers in coastal sediments, and their likely origins and potential for resuspension. In particular, measurements have been taken of linear alkylbenzenes (LABs), polycyclic aromatic hydrocarbons (PAHs), chlorinated hydrocarbon pesticides, including DDTs, and polychlorinated biphenyls in the sediments at a number of sites. Data are now available from 3 years of collection and analysis, including information on DDTs and polychlorinated biphenyls. The samples currently are being analyzed to quantify the PAHs and LABs, which will complete the sampling agenda for the project. These new data provide sufficient spatial coverage of the Santa Monica Bay to allow an estimation of sources, reservoirs, and dispersion of new and old materials (see following), as well as any short-term trends. The Watershed measurements will be augmented using archived data, as available, from the Sanitation Districts of the City of Los Angeles (e.g., Hyperion treatment plant monitoring samples) to construct a more general picture of sediment contamination throughout the bay.
In related work on the sources of trace compounds in coastal sediments, a novel analysis of DDT in bottom samples succeeded in separating the contributions due to sewage outflows and industrial dumping. The sewage source is identified through the close relationship that exists between DDT and another class of stable organic compounds used in detergents?the linear alkylbenzenes. Thus, using LABs as an indicator, coastal areas suffering industrial DDT pollution have been unequivocally identified. This information is being used to formulate remediation plans for the region.
All the results generated so far have been incorporated into the Watershed GIS database. The distribution pattern of specific contaminants clearly documents the transport of sewage into Santa Monica Bay. Also, it is evident that hot spots exist in the sediments where sewage particles preferentially accumulate close to discharge points. In sediments quite far south of the Hyperion outfall, relatively high amounts of DDTs have been found. These may be due to emissions from the Whites Point Outfall (used by the L.A. County Districts of Palos Verdes Shelf) rather than from Hyperion, owing to transport by the California Counter Current. This idea is being evaluated by examining additional data describing the DDT distributions on the Palos Verdes Shelf and adjacent sediments.
Integration: A Santa Monica Bay StudyThe four primary interdisciplinary components of the Los Angeles Watershed project, summarized above, are being further integrated in the context of an assessment of pollutant budgets in Santa Monica Bay. This unique effort will incorporate results from nearly all of the Watershed sub-projects obtained over the last 3 years. In addition, material from other sources will be used to fill gaps and produce a comprehensive Santa Monica Bay assessment. Figure 1 (below) illustrates the key elements of the analysis, which range from streamflow forced by climatological precipitation to transport and dispersion from Santa Monica Bay via the California current. In the simplest perspective, the bay represents a massive reservoir for pollutants (with several sub-reservoirs consisting of the surface layers, bulk waters, and sediments). The influxes and sinks for pollutants in the reservoirs are all addressed in the Watershed project, from atmospheric deposition to wastewater outfall to sediment dispersal. Major sources flow from the Malibu and Ballona watersheds, both of which have been extensively characterized by project scientists, from the hydrological to biological aspects. The coastal ocean circulation and eddy dispersion, likewise, has never before been represented in such great detail.
Table 1 indicates some of the areas that will link the four primary Watershed components in the final analysis. Although there are many linkages that could be established, the ones shown here (and in Figure 2) represent the natural connections that have evolved over the course of the project. A 3-year period is relatively short when building a broad interdisciplinary research program, especially where rigor is essential. However, the number and quality of the interconnections indicated in Figure 2, and proposed for the Santa Monica Bay assessment, achieve the stated expectations of the project.
Collaborations Established Under the Watershed Project
We have worked closely with the Southern California Coastal Water Research Project (SCCWRP) in making microlayer measurements, in planing for additional atmospheric deposition measurements, and in sediment studies. Other collaborations have been established with California EPA, in pollutant deposition research; the Monterey Bay Aquarium Research Institute (MBARI), to establish an instrumented buoy off the southern California coast for monitoring and model validation; Scripps Institute of Oceanography, for coastal and biogeochemical modeling and data assimilation studies; Rutgers University, for coastal ocean model development, and Long Island University for coastal biogeochemistry; Los Alamos National Laboratory, for watershed hydrological modeling; Livermore National Laboratory, for surface hydrological modeling; Los Angeles City Sanitation Districts and Orange County Sanitation Districts, for DDT tracer analysis; also the University of California Water Resources Center, University of California Sea Grant Program, Santa Monica Bay Restoration Project, CSIC Barcelona.
Table 1. Watershed components and relationships
Component (receptor) |
Ocean |
Air |
Land |
Wetlands |
Ocean |
Coastal ocean model; Marine ecosystems; Pollutant dispersion; Material mass budgets. |
Airborne deposition on coastal waters; Land deposition and runoff; Wind-driven currents. |
Urban runoff (SM Bay); Sewage outflow, dumping, and resuspension; Sediment flows (Malibu). |
Coastal marsh inputs (East Coast analogs); Fluxes of biotic materials and debris. |
Air |
Ocean-related winds (sea-breeze, land-sea winds); Marine aerosols and sulfur vapors. |
Material transport and transformation; Regional climatology; Winds and precipitation (e.g., Santa Ana winds). |
Topography and land use (roughness, moisture); Dust and gas emissions; Urban sources. |
Vapor fluxes from biological activity. |
Land |
Influence on climatology (El Nino, La Nina); Coastal erosion; Sediment relocation (coarse/fine sand). |
Precipitation means and extremes; Erosion and deposition of material; Climatology of drought. |
Hydrology and soils; Streamflow data and pred.; Runoff mass fluxes; River channels, land use; Malibu Creek case study. |
Exotic species; Malibu and Mugu Lagoon sediment studies. |
Wetlands |
Ocean forcing of tides and flushing; Role in drought cycles and impacts on estuaries. |
Deposition of nutrients and toxics; Precipitation direct impacts. |
Streamflow and flooding; Runoff of nutrients, toxics, organic compounds, and pesticides; Land use and development. |
Mugu/Newport/ Malibu plant/ animal studies; Ballona/SM Bay study; East Coast/West Coast analogs. |
A summary of information linking the four principal multidisciplinary components of the Los Angeles Watershed project. Each row indicates one of the four components and identifies the contributions of the other components (given in the specific columns). The diagonal entries define the primary elements of the four components. Integration is achieved by implementing various linkages (some of which are indicated in the table; also see Figure 2).
Figure 1. Schematic diagram indicating the elements of a mass balance analysis for Santa Monica Bay. Shown are sources and sinks of materials (soluble chemicals, particulates, trace metals, etc.) for Santa Monica Bay as treated in the Los Angeles Watershed Project. Input comes from the surrounding watershed runoff, sewage outfalls and deposition, and transport from adjacent waters. Losses occur by sedimentation, mixing, and dispersion into coastal currents. Input tends to be sporadic, while removal is more continuous, leading to major pollution ?events? and biological ?blooms.?
Figure 2. Interconnections between the major components of the Watershed Santa Monica Bay study. The connections on the left of the chart indicate intraconnectivity within components, and those to the right of the chart show the interconnectivity between components.
Future Activities:
The Los Angeles Watershed Santa Monica Bay assessment will be conducted in the summer and fall of 2000. The work will culminate with a 1-day workshop at UCLA?s IOE in early December 2000. Stakeholders in the Los Angeles watersheds, wetlands, and bay will be invited to participate. At the workshop, a draft of the final report focusing on the Santa Monica Bay assessment will be distributed for comment. Following the workshop, the report will be revised as needed, and published for distribution.
Journal Articles on this Report : 9 Displayed | Download in RIS Format
Other project views: | All 91 publications | 31 publications in selected types | All 23 journal articles |
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Type | Citation | ||
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Berk RR, Fovell R, Schoenberg R, Weiss R. Some statistical tools for evaluating computer simulations: A data analysis approach useful for environmental models. Climate Change 2000:1-17. |
R825381 (1999) |
not available |
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Boyer KE, Fong P, Vance RR, Ambrose RF. Salicornia virginica in a Southern California salt march: seasonal patterns and a nutrient-enrichment experiment. Wetlands 2001;21(3):315-326. |
R825381 (1999) R825381 (Final) R827637 (2002) R827637 (Final) |
Exit Exit |
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Boyer KE, Fong P. Macroalgal-mediated transfers of water column nitrogen to intertidal sediments and salt marsh plants. Journal of Experimental Marine Biology and Ecology 2005;321(1):59-69. |
R825381 (1999) R825381 (Final) R827637 (Final) |
Exit Exit Exit |
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Boyer KE, Fong P. Co-occurrence of habitat-modifying invertebrates: effects on structural and functional properties of a created salt marsh. Oecologia 2005;143(4):619-628. |
R825381 (1999) R825381 (Final) R827637 (Final) |
Exit Exit |
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Boyle KA, Kamer K, Fong P. Spatial and temporal patterns in sediment and water column nutrients in a eutrophic Southern California estuary. Estuaries and Coasts 2004;27(3):378-388. |
R825381 (1999) R825381 (Final) R827637 (2002) R827637 (Final) |
Exit |
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Forrester GE, Fredericks BI, Gerdeman D, Evans B, Steele MA, Zayed K, Schweitzer LE, Suffet IH, Vance RR, Ambrose RF. Growth of estaurine fish is associated with the combined concentration of sediment contaminants and shows no adaption or acclimation to past conditions. Marine Environmental Research 2003;56(3):423-442. |
R825381 (1999) R825381 (Final) |
Exit Exit |
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Kamer K, Fong P. A fluctuating salinity regime mitigates the negative effects of reduced salinity on the estuarine macroalga, Enteromorpha intestinalis (L.) link. Journal of Experimental Marine Biology and Ecology 2000;254(1):53-69. |
R825381 (1999) R825381 (Final) R827637 (2000) R827637 (Final) |
Exit Exit Exit |
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Kamer K, Boyle KA, Fong P. Macroalgal bloom dynamics in a highly eutrophic southern California estuary. Estuaries and Coasts 2001;24(4):623-635. |
R825381 (1999) R825381 (Final) R827637 (2000) R827637 (2002) R827637 (Final) |
Exit |
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Zeng EY, Venkatesan MI. Dispersion of sediment DDTs in the coastal ocean off southern California. Science of the Total Environment 1999;229(3):195-208. |
R825381 (1999) R825381 (Final) |
Exit Exit |
Supplemental Keywords:
watershed, groundwater, land, sediment, wetland, estuary, meteorology, waste, hydrology, geology, remote sensing, west, Los Angeles, RFA, Scientific Discipline, Geographic Area, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Nutrients, Water & Watershed, Hydrology, Geochemistry, Environmental Chemistry, Ecosystem/Assessment/Indicators, Ecosystem Protection, Contaminated Sediments, State, Ecological Effects - Environmental Exposure & Risk, Ecological Risk Assessment, Watersheds, aquatic ecosystem, coastal ecosystem, nutrient supply, remote sensing, basin hydrology, ecological exposure, wetlands, coastal watershed, meteorology, sediment, urban watersheds, contaminated sediment, Los Angeles Basin, coastal environments, sediment runoff, aquatic ecosystems, urbanizing watersheds, water quality, biogeochemistry, California (CA), groundwater, land useProgress 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.