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Nutrient Export Coefficient Modeling in Mediterranean Coastal Streams

Nutrient Export Coefficient Modeling in Mediterranean Coastal Streams. Timothy H. Robinson, Al Leydecker, Arturo A. Keller and John M. Melack Bren School of Environmental Science & Management University of California, Santa Barbara, USA. UC Marine Council. Santa Barbara Coastal

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Nutrient Export Coefficient Modeling in Mediterranean Coastal Streams

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  1. Nutrient Export Coefficient Modeling in Mediterranean Coastal Streams Timothy H. Robinson, Al Leydecker, Arturo A. Keller and John M. Melack Bren School of Environmental Science & Management University of California, Santa Barbara, USA UC Marine Council Santa Barbara Coastal LTER - NSF

  2. SF LA Study Area Watershed Characteristics

  3. Climatic Regime

  4. 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 every 2 weeks during the dry season • Once a week during the wet season • Storm sampling: • Every hour on the rising limb of the hydrograph • Every 2-4 hours on the falling limb of the hydrograph Project duration: WY2001, WY2002 and WY2003

  5. Annual Basin Nutrient ExportWater Year 2001 and 2002

  6. E A GIS Datm LTER Datm Literature I Interview I Literature K Literature L S+P k t d/v a LU GIS Nutrient Export Coefficient Model (NEC-M) • Abbreviation key: • L – Nutrient Export (loss) (mass area-1 time-1) • E – Export Coefficient Function • b – Watershed Response Variable • LU – Land use • S – Soils • P – Precipitation • A – Land Use Area • I – Nutrient input rate • K – Down Stream Distance-Decay Function • k and a – Coefficients • t – Time • d – Distance Traveled Downstream • v – Average Velocity Traveled • Downstream • Datm – Atmospheric deposition

  7. Sampling Site Locations WY2001 WY2002 WY2003 • Land Use: • Chaparral/Forest • Avocado • Greenhouse • Nursery • Residential • Commercial

  8. Spatial Extent of Land Use Class (A) 6

  9. Nutrient Export WY2002 • Hourly time-step • Hydrology: • Pressure Transducer • Observed stage • HEC-RAS • Stream Chemistry • Modeling

  10. E S+P LU GIS Nutrient Export Coefficient (E) Franklin Creek E – Export Coefficient Function b – Watershed Response Variable S – Soils P – Precipitation

  11. Scaling the Export Coefficient (b) • Storm to Storm relationships. • Volume Weighted Mean Concentrations vs. Cumulative Rainfall. • Volume Weighted Mean Concentrations vs. Rainfall/Runoff Ratio. • Topographic Index (TI): variable source area. • Antecedent Soil Moisture Content: SSURGO soils data, texture->porosity, infiltration rates, evapotranspiration rates, depth to impervious layer, etc.

  12. Nutrient Flux (normalized by runoff) WY2002

  13. VWM vs. Runoff/Rainfall

  14. Conclusions • High frequency storm sampling is critical. • Nutrient Export Coefficients in Mediterranean climates must be a function that is related to the watershed runoff response and not a single annual term. • Analysis of the final year of data will solidify scaling techniques in NEC-M. • Future work: implement the model in the study watersheds and test its portability in a catchment outside of the area (e.g. Spain).

  15. Questions Thank you !

  16. Nutrient Watershed Flux

  17. Linkage – Stream Network & Chemistry • Arc Hydro Geodatabase:geometric network representation of the connectivity of surface water • HydroNetwork • HydroEdge • HydroJunctions • SchematicLinks+Nodes • HydroPointEvent • HydroLineEvent Drainage Network + Sampling Points DEM analysis MS Excel/Access: Visual Basic for Application:

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

  19. 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)

  20. Precipitation WY2002

  21. Nutrient Flux (normalized by runoff) WY2002

  22. K Literature k t D/V a Attenuation (K) • Distance from stream • Distance from basin outlet • Type of riparian corridor • Dispersal Area and Trapping Likelihood (BI Index)

  23. VWM vs. Cumulative Rainfall VWM - Volume Weighted Mean

  24. VWM vs. Cumulative Rainfall VWM - Volume Weighted Mean

  25. VWM vs. Runoff/Rainfall

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