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Timothy H. Robinson John M. Melack Arturo A. Keller

Nutrient Concentrations in Coastal Streams, Variation with Land Use in the Carpinteria Valley (Santa Barbara Coastal LTER). Timothy H. Robinson John M. Melack Arturo A. Keller Bren School of Environmental Science and Management University of California Santa Barbara. Outline of the talk.

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Timothy H. Robinson John M. Melack Arturo A. Keller

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  1. Nutrient Concentrations in Coastal Streams, Variation with Land Use in the Carpinteria Valley(Santa Barbara Coastal LTER) Timothy H. Robinson John M. Melack Arturo A. Keller Bren School of Environmental Science and Management University of California Santa Barbara

  2. Outline of the talk Project overview Sampling strategy and location Measuring stream nutrient concentrations and flow Nutrient loading and the development of a flux model Basin outlet mass flux Comparison of nutrient loading by land use type Nutrient export coefficient modeling Integration with an urban growth model

  3. Project Overview

  4. Methodology Identify land use classes and sampling site locations: Chaparral/Forest, Avocado, Greenhouse, Open-Field Nursery, Residential and Commercial Sampling strategies: Subcatchment, point discharge and above-below Sampling methods: Manual sample or ISCO auto-sampler GIS database development Data analysis Nutrient flux calculation (hydrology and stream chemistry) Nutrient export coefficient model development Integration with an urban growth model

  5. Sampling Site Locations

  6. Measuring Nutrient Concentrations Grab samples and ISCO auto- samplers

  7. Specifics: • Analyzing for: • Ammonium (NH4+), Nitrate (NO3-), Total Dissolve Nitrogen (TDN), Phosphate (PO43-), Total Particulate Carbon (TPC), Total Particulate Nitrogen (TPN), Total Particulate Phosphate (TPP), Total Suspended Sediments (TSS) and major ions at selected locations • Frequency: • Regular sampling: • Once a week during the wet season • Once every 2 weeks during the dry season • Storm sampling: • Every hour on the rising limb of the hydrograph • Every 2-4 hours on the falling limb of the hydrograph

  8. Measuring Stream Flow Staff Gauges and Pressure Transducers Surveying the Cross-Sections Developing Rating Curves

  9. Stream Chemistry and Hydrology Carpinteria Creek (WY-2002)

  10. 10000 baseflow stormflow 1000 100 nitrate (µM) 10 1 Franklin Carpinteria Santa Monica 100 baseflow stormflow 10 phosphate (µM) 1 Franklin Carpinteria Santa Monica General Trends in Nutrient Concentrations by Watershed

  11. Nutrient Loading Development of a Nutrient Flux Model Stream Chemistry Observed Stage PT Stage (5-min) Stage-Discharge Relationship (HEC-RAS) Stream Chemistry Observed Flow PT Flow (5-min) Flow (hourly) Stream Chemistry (hourly) Observed Flow (hourly) Flow (hourly) Identify: Baseflow, Peakflow.. Nut. Conc. Stream Chemistry (model/obs) Flow (hourly) Linear extrapolation Annual Nutrient Loading Nut. Flux (conc/flow)

  12. Modeled vs. Observed Residential - CP30

  13. Cumulative Nitrate ExportNursery Site

  14. Basin Nutrient Export Franklin Creek Watershed WY 2001

  15. WY2001 Basin Outlet Mass Flux WY 2001

  16. Comparison of Flux afterNormalizing with Runoff

  17. S+P +ASMC Nutrient Export Coefficient Model E A GIS Datm LTER Datm Literature I Interview I Literature K Literature L k t D/V a LU GIS • Abbreviation key: • E – Export Coefficient Function • B – Watershed Response Variable • S – Soils • P - Precipitation • ASMC – Antecedent Soil Moisture Content • K – Down Stream Distance-Decay Function • k + a – Coefficients • t – Time • D – Distance Traveled Downstream • V – Average Velocity Traveled • Downstream

  18. Integration with an Urban Growth Model (SLEUTH) • SLEUTH : an urban growth model implemented for the Santa Barbara area that predicts future land use, example 2050 • Enables comparison of future loadings to standards being set for stream water quality regulations (TMDLs) • Evaluation of proposed BMP mitigations

  19. Conclusions • Stream nutrient concentrations only partially tell the story • Hydrology is the critical element of any flux calculation, which is necessary • to characterize nutrient loading • The finer the sampling strategy the better the results, particularly with urban/agriculturally dominated sites • Creating a dedicated and enthusiastic group of stream samplers is a crucial component of any project of this nature • Nutrient export coefficients for a Mediterranean climate need to accommodate the high inter/intra-year storm variability • A minimum of two years of data are needed to statistically validate model results • Hope for rain!!

  20. Questions Thank you

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