Watershed Monitoring and Modeling in Switzer, Chollas, and Paleta Creek Watersheds Kenneth Schiff Southern California Coastal Water Research Project

By The End Of Today Overview from previous meetings Review wet season empirical results Demonstrate success at building watershed models Assessment guidance so SCCWRP can write final report

At Our Previous Meetings Sediments at the mouth of several urban creeks draining to SD Bay are listed as impaired - chemistry, toxicity, benthic community Two questions for this study -What are the loads of COPC to the creek mouth? -How much of the total load deposits in the creek mouth? Several COPC -Chlordane, PAHs, PCBs, Cu, Pb, Zn, -As, Hg

Sources of COPC Chollas Creek watershed - Paleta and Switzer Creek watersheds Runoff directly to the Chollas Creek mouth -Navy, NASSCO Atmospheric deposition to the creek mouth San Diego Bay - tidal inputs

Watershed Inputs Break into two parts Use combination of empirical data and wet weather modeling -TSS, metals, PAHs -Can we predict changes in loads and concentrations? Use empirical data -Chlorinated hydrocarbons -Can we detect loads or concentrations?

Sampling Design for Wet Weather Four sites - North and South Fork Chollas, Switzer, Paleta Three storms each - continuous flow data Pollutograph for model validation -10 to 12 samples per site event -TSS, metals, and PAH Flow weighted composites for non-modeled components - large volume samples for low detection limits

Insert maps….

* * * * Sampled event

(mg/L)

SwitzerNorth Chollas South Chollas Paleta TSS (mg/L) Copper (ug/L) Lead (ug/L) Zinc (ug/L) Total PAH (ng/L)5581, Tot Chlordane (ng/L) Total PCB (ng/L)ND Annual Flow Weighted Mean

By The End Of Today Overview from previous meetings Review wet season empirical results Demonstrate success at building watershed models Assessment guidance so SCCWRP can write final report

Approach to Building a Watershed Model Physical data for the model domain - watershed delineation, stream properties, land use, etc. Calibrate flow and water quality at small homogeneous land uses -utilize land use data from Los Angeles Validate flow and water quality at the end of the watershed - cumulative of all land uses

Sampling Design for Wet Weather Four sites - North and South Fork Chollas, Switzer, Paleta Three storms each - continuous flow data Pollutograph for model validation -10 to 12 samples per site event -TSS, metals, and PAH Flow weighted composites for non-modeled components - large volume samples for low detection limits

Paleta Creek

Hydrologic Calibration and Validation Modeled at hourly time steps -Hourly averages Hydrographs Hydrograph simulations Assess accuracy, bias, precision

South Chollas Creek

Runoff Volume

Peak Flow Mean Flow

Water Quality Calibration and Validation Modeled at hourly time steps -Hourly averages Pollutographs - simulations Event mean concentrations Accuracy, bias, precision

South Chollas Creek

South Chollas Creek TSS

South Chollas Creek Lead

North Chollas Creek Lead

Lead Zinc Copper

ACCURACY (# Overlap CI’s) BIAS (% Relative to Actual) PRECISION (Coeff of Var) Copper9/ Lead11/ Zinc9/ Total PAH7/ ,744 Modeled versus Measured EMCs

Long Term Model Runs Decadal simulation to 2006 All four watersheds All constituents Example output -what other simulations do we want?

Chollas Ck Switzer Ck Paleta Ck

Average Annual Pollutant Loads PollutantChollasPaletaSwitzer Copper (kg) Lead (kg) Zinc (kg) PAHs (kg) Chlordane (g) PCBs (g) Arsenic (kg) Mercury (kg)

Chollas Creek Switzer Creek Percent Landuse Loadings for Copper Paleta Creek

Load Reduction Scenarios Assumed BMP Storage 22% Reduction 44% Reduction

Sources of COPC Chollas Creek watershed - Paleta and Switzer Creek watersheds Runoff directly to the Chollas Creek mouth -Navy, NASSCO Atmospheric deposition to the creek mouth San Diego Bay - tidal inputs

Sampling Design for Atmospheric Deposition Focus was deposition onto the water surface of creek mouth One site as close to creek mouth as possible -Minimum of 8 sample events Use surrogate surfaces for metals Use high volume samplers for organics -Supplement with water samples for diffusion estimates

Comparison Among Sources Copper

Wet Weather of Summary Successfully completed wet weather sampling from last season Empirical data for all constituents at all watersheds Developed a dynamic model -flow and water quality Accuracy, bias, and precision near expectations -EMCs versus pollutographs Modeled long term pollutant loads - additional model runs?

Atmospheric Dry Deposition Summary Successfully completed dry deposition sampling from last summer San Diego > other harbors in So Cal -direct dep of metals small relative to wet weather at Chollas Ck mouth Estimates of dry deposition for organic constituents is nearly finished

Upcoming Work Focused goal on creek mouth modeling - How much of the total load deposits in the creek mouth? Designed study plan last year - SCCWRP and Navy collaboration Enhance existing Bay model for Chollas Creek mouth -Use our new watershed model for inputs -Increased spatial resolution Concentrate on particle (and associated COPCs) dynamics -Deposition is mostly a function of settling

Wet Season Sampling Wet weather runoff from Chollas Ck -Large volume samples for particle separation and COPC analysis Creek mouth sampling for hydrodynamics -Three dimensional plume mapping Creek mouth sampling for particle dynamics -in situ particle size measurements Creek mouth sampling for COPCs -Large volume samples for low detection limits

Next Steps Final watershed model runs Complete atmospheric deposition analysis Draft Loading Report by March Creek mouth sampling -one dry weather, two storm events

Annual Flow Weighted Mean SwitzerN ChollasS ChollasPaleta TSS (mg/L) Copper (ug/L) Lead (ug/L) Zinc (ug/L) Total PAH (ng/L)5581, Tot Chlordane (ng/L) Total PCB (ng/L)ND Arsenic (ug/L) Mercury (ug/L)

Chollas Creek Switzer Creek Percent Landuse Loadings for Lead Paleta Creek

Chollas Creek Switzer Creek Percent Landuse Loadings for Zinc Paleta Creek