UC Marine Council Santa Barbara Coastal LTER - NSF 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

Watershed Characteristics Study Area LA SF

Climatic Regime

Analyzing for: Ammonium (NH 4 + ), Nitrate (NO 3 - ), Total Dissolve Nitrogen (TDN), Phosphate (PO 4 3- ), Total Particulate Carbon (TPC), Total Particulate Nitrogen (TPN), Total Particulate Phosphate (TPP), Total Suspended Sediments (TSS) and major ions at selected locations Specifics: 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

Annual Basin Nutrient Export Water Year 2001 and 2002

Abbreviation key: L – Nutrient Export (loss) (mass area -1 time -1 ) E – Export Coefficient Function  – Watershed Response Variable LU – Land use S – Soils Nutrient Export Coefficient Model (NEC-M) P – Precipitation A – Land Use Area I – Nutrient input rate K – Down Stream Distance-Decay Function k and  – Coefficients t – Time d – Distance Traveled Downstream v – Average Velocity Traveled Downstream D atm – Atmospheric deposition AGISE IInterviewILiteratureKLiterature  k td/v LUGIS D atm LTER Literature S+P L

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

Spatial Extent of Land Use Class (A) 6

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

E – Export Coefficient Function  – Watershed Response Variable S – Soils P – Precipitation Nutrient Export Coefficient (E) E LUGIS S+P Franklin Creek

Scaling the Export Coefficient (  ) 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.

Nutrient Flux (normalized by runoff) WY2002

VWM vs. Runoff/Rainfall

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).

Questions Thank you !

Nutrient Watershed Flux

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 Visual Basic for Application: MS Excel/Access: DEM analysis

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

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

Precipitation WY2002

Nutrient Flux (normalized by runoff) WY2002

Attenuation (K) KLiterature  k tD/V Distance from stream Distance from basin outlet Type of riparian corridor Dispersal Area and Trapping Likelihood (BI Index)

VWM vs. Cumulative Rainfall VWM - Volume Weighted Mean

VWM vs. Cumulative Rainfall VWM - Volume Weighted Mean

VWM vs. Runoff/Rainfall