Watershed Modeling of Copper Loads to San Francisco Bay

Transcription

1 Watershed Modeling of Copper Loads to San Francisco Bay Tony Donigian AQUA TERRA Consultants Brake Pad Partnership Stakeholder Conference July 31, 2007

2 Watershed Model Objectives - Provide daily loadings of flow, total suspended solids, and copper to the bay model - Use model to estimate relative contribution of brake pad wear debris

3 Critical Elements of Project Approach Abide by existing approved work plan Use available Brake Pad Partnership work products, e.g. copper sources report, air deposition rates, impervious area studies Respond to peer review comments Leverage recent/current modeling/data efforts: Alameda Countywide Clean Water Program-sponsored Bay Area Hydrology Model watersheds and database Current Santa Clara Valley Urban Runoff Pollution Prevention Program watershed and data efforts Current BASINS meteorological data expansion work

4 HSPF: Hydrologic Simulation Program - FORTRAN Continuous simulation model Natural and developed watersheds and water systems Land surface and subsurface hydrology and quality processes Stream/lake hydraulics and water quality processes Time series data management and storage Time series data statistical analysis and operations Core watershed model in EPA BASINS and Army Corps WMS Development and maintenance activities sponsored by U.S. EPA and U.S. Geological Survey

5 Bay Area Watersheds and Study Area

6 Watershed and County Boundaries, Hydrography, and Reservoirs

7 Watershed Boundaries Drainage divided into 22 watersheds San Francisco proper not included Some watersheds are not shown as directly connected to Bay, connection is implemented in model Selected watersheds were further subdivided for adequate modeling Areas behind significant reservoirs were not included (similar to past efforts)

8 Reservoirs and Drainage Areas Not Included in Watershed Model (similar to past studies)

9 Meteorological Data Needed for Modeling Precipitation hourly Evaporation for potential evapotranspiration

10 Isohyetal Pattern Precipitation Gages and Thiessen Analysis

11 Available Daily Evaporation Stations

12 California Irrigation Management Information Systems Evapotranspiration Zones for the Bay Area Los Alamitos

13 Land Use

14 Land Use Categories Modeled Bay Area Hydrology Model Forest Shrub/Wooded Grass/Wetland Developed Landscape Impervious Agriculture

15 Model Land Use Distribution (based on 1992 NLCD)

16 Land Use Categories in the Model Forest 26.4% Shrub/Wooded 7.0% Grass/Wetland 34.5% Developed (pervious only) 18.9% Impervious (DCIA) 4.8% Agriculture 8.4%

17 NRCS Hydrologic Soil Groups for the Bay Area

18 Basis for Model Parameterization Land use, soils, and slope coverages Bay Area Hydrology Model calibration watersheds in Alameda and Santa Clara Counties Prior model application for flow, total suspended solids, and copper runoff in Calabazas Creek Model calibration in Castro Valley watershed for flow, total suspended solids, and copper

19 Copper Fluxes in the Watershed Model BPWD: Wet/Dry Wet (in precipitation); Dry (constant flux) Non-BPWD Release to Developed Non-BPWD Release to Agriculture BPWD Developed Roadway Impervious Agriculture Grassland Pervious ( Street ) Sweeping Removed Shrubland/ Woodland Forest Non-BPWD Arch. & Industrial Runoff (Rain-Dependent) (calculated from impervious runoff and concentration) STREAMS Bay Model Copper Releases (Not Dependent on Rain) pseudo point-source

20 Model Operation/Application HSPF Model set up for each of 22 watersheds Some calibration and consistency checks were performed for flow for selected USGS gages Some calibration was performed for Castro Valley watershed for total suspended solids and copper Consistency checks (weight-of of-evidence) performed for other watersheds with monitoring data Model runs were simulated for 25 years, Oct 1980 September 2005 Model runs performed for each of 6 scenarios

21 USGS Flow Gages Used for Consistency Checks

22 Flow Duration Model-Data Comparisons Colma Creek San Francisquito Creek Napa River near Napa Alameda Creek

23 Model-Data Comparisons for Flow Volumes Mean Mean Mean Simulated Observed Rainfall Flow Flow Residual Percent Period of (inches) (inches) (inches) (inches) Error Record Napa River % Sonoma Creek % Guadalupe River % Corte Madera Creek % San Francisquito Creek % Colma Creek % San Lorenzo Creek % Alameda Creek % 81-05

24 Total Suspended Solids & Copper Calibrations for Castro Valley Creek TSS, mg/l Cu, ug/l Courtesy of J. Carleton, US EPA Slope=.99; R 2 =.66

25 Model Scenarios - Concept Objective: Assess relative contribution of brake pad wear debris in copper loads to the Bay Approach: Run model with and without brake pad wear debris contributions

26 Model Scenarios Brakes Midpoint best estimate of all copper sources and associated uncertainty Brakes High High end of BPWD sources and low end of non-bpwd sources Provides an estimate of the upper boundary of the relative contribution from brake pads Brakes Low Low end of BPWD sources and high end of non-bpwd sources Provides an estimate of the lower boundary of the relative contribution from brake pads Each scenario also run without BPWD contributions, i.e. 6 scenarios simulated

27 Watershed Model Loads to San Francisco Bay Best Estimate (Mid-Brakes) Scenario Mid Brakes Load to Bay Mid Brakes - No BP Load to Bay Contra Costa Central 4,669 3,564 Contra Costa West 1,941 1,549 Coyote Creek 3,074 1,937 East Bay Central 5,849 3,823 East Bay North 1,781 1,144 East Bay South Marin North Marin South 1, Napa 9,174 8,372 North Napa 0 0 North Sonoma 0 0 Peninsula Central 2,682 1,372 Petaluma 4,742 4,410 Santa Clara Valley Central 2,645 1,899 Santa Clara Valley West 4,392 2,603 Solano West 1,694 1,333 Sonoma 4,796 4,550 Upper Alameda 3,480 2,931 Upper Colma Upper Corte Madera Upper San Francisquito San Lorenzo Creek Totals 56,465 43,632

28 Summary of Mean Annual Copper Loads to Bay Scenarios High Brakes Mid Brakes Low Brakes Copper Loads to SF Bay BP Contributions Non-BP Contributions Total Loads kg % kg % 19,547 35% 36,360 65% 55,907 12,833 23% 43,632 77% 56,465 5,854 10% 50,914 90% 56,769

29 Contribution of Loads to San Francisco Bay for Best Estimate Scenario

30 Mean Annual Copper Fluxes in the Watershed Model (1000 kg/y) BPWD: Wet/Dry Wet (in precipitation); Dry (constant flux) 1.7 Non-BPWD Release to Developed 5.1 Non-BPWD Release to Agriculture BPWD Developed Roadway Impervious Agriculture Grassland Pervious ( Street ) Sweeping Removed Non-BPWD Arch. & Industrial Runoff (Rain-Dependent) (calculated from impervious runoff and concentration) (60) STREAMS 57 Bay Model Shrubland/ Woodland Copper Releases Forest (Not Dependent on Rain) Pseudo point-source

31 Comparisons with Other Load Estimates Sediment Loads SFEI (McKee et al, 2003): Range of 561,000 to 1,000,000 tonnes/yr total suspended solids Model estimates: 931,000 tonnes/yr Copper Loads SFEI (Davis et al, 2000): Estimate of 66,000 kg/yr Model estimates: 56,465 kg/yr

32 Summary Brake Pad Partnership studies provided copper source estimates for input to the watershed model Existing data sources (meteorological, land use, soils, hydrography,, etc.) were used to set up models of 22 watersheds Recent HSPF modeling studies provided basis for parameterization throughout the Bay Area Calibration and consistency checks comprised the weight-of of- evidence approach to model application Model results are shown to be consistent with other similar studies, and provide reasonable loads to the bay model Brake pad contributions were estimated to range from 10% to 35% of total copper loads to the Bay

33 Questions/Discussion