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Hierarchical regulation of nitrogen export from urban catchments in central Arizona-Phoenix

Publication date: 2009

Author(s):

  • David Lewis, Arizona State University
  • Nancy Grimm, Arizona State University

Abstract:

In urban catchments of arid central Arizona, we investigate how the export of mineral and organic nitrogen (N) in storm runoff is regulated by interactions between local landscape characteristics and broader scale storm features. First, we test whether N export is more a function of (1) processes that affect N concentration in runoff or (2) the propensity of the catchment to convey rainfall as runoff. With data pooled across catchments, the mass of N in export (load) is determined by processes regulating runoff N concentration. There are exceptions when catchments are examined individually, where N load from some catchments is determined by the hydrologic responsiveness of the catchment. Second, we investigate the relationship between N export and catchment features. Loads per catchment area were greater from more impervious catchments, probably because impervious catchments held more N in a mobilizable phase and conveyed more rainfall as overland flow. Loads per area were lower from larger catchments, possibly owing to more N-retention hot spots in larger catchments. Catchments with the greatest N exports were those with commercial land use, and loads decreased as development became less prevalent or as residential replaced industrial land use. Third, we investigated how catchment features moderated direct responses of N export to storms. Export was less correlated with storm features in catchments that were larger, more pervious, and less industrial. Results support an N build and flush hypothesis, which purports that there is little biotic processing of N deposited to arid, urban surfaces with little organic matter. The rate and duration of deposition determine the size of the mobile N pool. Any amount of rainfall capable of generating overland flow would entrain nearly all mobilizable N and export it from the catchment. Nonetheless, these results suggest that, even with daunting seasonal and interannual variability in storm conditions, material export can be reduced by managing intrinsic catchment features.


Keywords:


Temporal Coverage:

1991-01-01 to 2005-03-01

Geographic Coverage:

Geographic Description: Phoenix metropolitan area
Bounding Coordinates:
Longitude:-112.794316 to -111.566698
Latitude:33.838010 to 33.198342

Contact:

Information Manager, Global Institute of Sustainability, Arizona State University, 
POB 875402,TEMPE
 caplter.data@asu.edu

Methods used in producing this dataset: Show


Data Files (2) :

Tabular: 74_sites_1.csv

Description: Descriptions of Catchments

Column Description Type Units
id record ID
float
site_id abbreviation of site name
string
location location within Phoenix metropolitan area
string
contrib_area_km2 area contributing to runoff
float squareKilometers
perc_residential Residential landuse in catchment in percent area
float dimensionless
perc_industrial Industrial landuse in catchment in percent area
float dimensionless
perc_commercial Commercial landuse in catchment in percent area
float dimensionless
perc_developed Developed landuse in catchment in percent area
float dimensionless
perc_undeveloped Undeveloped landuse in catchment in percent area
float dimensionless
perc_impervious Impervious ground cover in catchment in percent area
float dimensionless
landfac1 Factor 1 factor scores from a factor analysis for data reduction
float
landfac2 Factor 2 factor scores from a factor analysis for data reduction
float
landfac3 Factor 3 factor scores from a factor analysis for data reduction
float

Tabular: 74_storm_events_1.csv

Description: Nitrogen concentraitions in storm runoff events

Column Description Type Units
ID Automatically generated sequential ID number
integer
site_id site ID as used in sites table
string
month Month of storm event
float nominalMonth
year Year of storm event
float nominalYear
day Day of storm event 1 is 1991-01-01
float number
discharge_l Discharge during collection
float liter
area_corr_discharge_megl_km2 Discharge corrected for area
float megaLiterPerKilometerSquared
season Season during which the storm event occurred
string
dry_days Days without precipitation preceeding the storm event
float number
precipitation_cm Total precipitation during the storm event
float centimeter
precip_intens_cm_5min Precipitation intensity in cm per 5 minutes
float centimeterPerFiveMinute
storm_duration_min Storm duration in minutes
float nominalMinute
no3_conc_mg_l NO3 concentration in runoff Event-mean concentration of N as NO2 and NO3
float milligramsPerLiter
nh4_conce_mg_l NH4 concentration in runoff Event-mean concentration of N as NH4
float milligramsPerLiter
organic_n_conc_mg_l Organic N concentration in runoff Event-mean concentration of N as organic N
float milligramsPerLiter
tot_n_concentration_mg_l Total N concentration in runoff Event-mean concentration of N
float milligramsPerLiter
no3_load_kg_km2 Mass of N as NO2 and NO3 exported from the catchment during the storm
float kilogramPerKilometerSquared
nh4_load_kg_km2 Mass of N as NH4 exported from the catchment during the storm
float kilogramPerKilometerSquared
org_n_load_kg_km2 Mass of N as organic N exported from the catchment during the storm
float kilogramPerKilometerSquared
tot_n_load_kg_km2 Mass of N (all forms) exported from the catchment during the storm
float kilogramPerKilometerSquared
landfac1_season Landfactor 1 storm attribute interaction term season
float dimensionless
landfac1_dry_days Landfactor 1 storm attribute interaction term precipitation
float dimensionless
landfac1_precip Landfactor 1 storm attribute interaction term dry days
float dimensionless
landfac2_season Landfactor 2 storm attribute interaction term season
float dimensionless
landfac2_dry_days Landfactor 2 storm attribute interaction term dray days
float dimensionless
landfac2_precip Landfactor 2 storm attribute interaction term precipitation
float dimensionless
Landfac3_season Landfactor 3 storm attribute interaction term season
float dimensionless
Landfac3_dry_days Landfactor 3 storm attribute interaction term dry days
float dimensionless
Landfac3_precip Landfactor 3 storm attribute interaction term precipitation
float dimensionless

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