Nutrient fluxes from coastal California

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Nutrient fluxes from coastal California catchment
s with suburban development

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Santa Barbara Channel LTER
Linking catchments to coastal waters
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Objectives

• Examine episodic, seasonal and interannual
  aspects of fluvial fluxes in catchments with
  suburban development along the coast of central
  California
• Comparison to agricultural and chaparral
  catchments

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Coastal catchments of Santa Barbara Channel - New
Santa Barbara Channel
Los Angeles, CA
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City of Santa Barbara, CA
Gaviota
Refugio
El Capitan
San Onofre
Arroyo Hondo
Bell
Mission
Devereux
Arroyo Burro
Tecolotito
Santa Monica Franklin
Carpinteria
Los Carneros
Rincon
Atascadero
Santa Barbara Channel
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Land use among catchments
From West to East
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Sub-Watershed Scale
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Short streams steep terrain easily eroded
rock and soil flashy stormflow with lots of
sediment
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• Hydrological and hydrochemical measurements
• Stage and temperature (continuous)
• Nitrate, ammonium, phosphate,
• dissolved nitrogen (weekly and event)

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• Mediterranean climate Almost all the rainfall
  occurs during 3 winter months
• MoMediteranean climate Almost all the rainfall
  occurs during 3 winter months
• More than half of a years flow can occur during
  one storm in less than 24 hrs.
• re than half of a years flow can occur during
  one storm in less than 24 hrs.

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Single storm hydrograph and solute variations
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(No Transcript)
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Cumulative Export, Arroyo Burro Creek, WY 2001
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Land use differences produce order-of-magnitude
variations in nutrient concentrations
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WY 2001
Industrial Agriculture
Urban
Dissolved
Light Agriculture
Urban, Non-channelized
Particulate
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Sampling Sites (Land Use Types)
T. Robinson 2006
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Parcel Scale Residential Site

• T. Robinson 2006

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Parcel Scale Greenhouse Site

• T. Robinson 2006

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Nutrient Export by Land Use NO3-N
Annual

• T. Robinson 2006

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Nutrient Export by Land Use PO4-P
Annual

• T. Robinson 2006

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Hydrologic Modeling

• Compile/Develop Spatial Data
• Topography (DEM)
• Drainage Network (Stream and Drains)
• Land Use (Digital Images and Parcels)
• Soils (SSURGO)
• Estimate Rainfall Coverages
• Rain Gauge Network
• Orographic Enhancement
• Setup HEC-HMS Model
• Sub-divide watersheds
• Determine spatially averaged parameters

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Hydrologic Model

• HEC-HMS Model
• Spatially averaged parameters
• Event based
• Surface Response
• Impervious surfaces
• Infiltration excess
• Subsurface Response
• Rapid shallow soil flow (interflow)
• Slower groundwater discharge (baseflow)
• Flow Routing
• Overland
• Channel

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HEC-HMS Model Results
Mission Creek at Mission St. USGS Gauge No.
11119745 March 4-7, 2001
HEC-HMS Simulation
USGS Gauge Data
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Regression models of export

• Models developed for annual, daily and storm
  export
• Based on area in agriculture,
• urban use (impervious surface),
• discharge

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Interannual variations in nitrate fluxes among
catchments
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Conclusions

• Large variations in N and P concentrations among
  streams related to differences in coastal plain
  land use
• Export is determined by discharge with the few
  large storms dominating annual flux
• Runoff can be modeled on an individual storm
  basis with rainfall data and catchment
  characteristics
• On-going measurements in nearshore waters and
  models of nearshore physical processes will
  integrate fluvial export with kelp ecosystem
  function

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The impact of fire on hydrology and suspended
sediment and nutrient export in southern
California chaparral watersheds
)
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Gaviota Wildfire June 5 to 12, 2004
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San Onofre Creek
Stream Sampling
February19, 2005
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Stream Gauging
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Changes to Hydrologic Response

• Infiltration decreases
• formation of hydrophobic soil layer
• compaction of soil
• Evapotranspiration and Interception decrease
• more rainfall is available for runoff

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San Onofre Creek
October 26, 2004
October 19, 2004
November 15, 2004
December 28, 2004
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San Onofre Creek
January 7, 2005
January 26, 2005
February 22, 2005
February19, 2005
April 27, 2005
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Changes to Sediment Export

• Infiltration decreases
• Runoff and peak discharge increase
• Interception decreases due to vegetation loss

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Sediment movement in San Onofre
Photos taken May 2005
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Changes in Phosphate Export

• Phosphate is rapidly mineralized and deposited on
  soil surface but is not as mobile as nitrate
• Increases in phosphate concentration in runoff
  roughly correlates with peak discharge

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Summary of Results

• Hydrology
• Hydrologic response was typical for southern
  California chaparral during early season storms
  but differences decreased as the season
  progressed with above average rainfall.
• Suspended Sediment
• 10-fold increase in suspended sediment export
• Nutrients
• 30 times increase in ammonium export
• 5.5 times increase in nitrate export
• 2.8 times increase in DON export
• 2 times increase in phosphate export