An open source version of the
Nonpoint-Source Pollution and Erosion
Comparison Tool
Climate Tools Café Webinar
Dave Eslinger, Ph.D.
3 May, 2012
What is OpenNSPECT?
• Water quality screening tool
• Spatially distributed (raster-based) pollutant
and sediment yield model
• Compares the effects of different land cover
and land use scenarios on total yields
• User friendly graphical interface within a GIS
environment
Processes Simulated
• Topography determines flow
direction and slope
• Soil characteristics, land
cover, and precipitation
determine runoff
• Runoff, land cover, and
pollutant coefficients
determine pollutant loads
• Runoff, topography, soil
characteristics, and land
cover determine sediment
loads
Uses Existing Approaches
• Rainfall runoff
– Soil Conservation Service (SCS)
curve number technique
• Nonpoint pollutant
– Event mean concentration
technique
• Sediment erosion
– Universal Soil Loss Equation
(USLE)
• Modified (MUSLE)
• Revised (RUSLE)
Assumptions/Limitations
• Omitted processes
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–
–
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Stormwater drainage
Stream diversions
Snowmelt
Landslides
• No time component for
– Runoff dynamics
– Sediment redeposition
– Pollutant dynamics
Source: NASA Earth Science Enterprise
Usage Example
• Kingston Lake
Watershed
Association, near
Conway, SC
• Nutrient loads
under different
growth scenarios
Data Needs
• National sources*
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–
–
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–
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Land cover data
Topography
Precipitation
Soils data
Pollutant coefficients
Rainfall erosivity
• Local sources
– Water quality standards
– Additional pollutant
coefficients
*Local “tuning” improves accuracy
Topography
• Defines flow direction,
stream networks,
watersheds
• Default
– U.S. Geological Survey
(USGS) 30 m resolution
digital elevation model
• Resolution impacts
processing speed and
file size
Land Cover
• Foundation for runoff
quantity, sediment yield,
pollutant yield
• Default
– Coastal Change Analysis
Program (C-CAP)
– 30 m resolution
• Flexible
– Can easily substitute any
land cover grid
Soils
• Runoff and erosion
estimates are dependent
upon soils and land
cover
• Default
– SSURGO soils†
– County level resolution
• Infiltration rate
– Hydrologic group
• Soil erodibility
– K-factor
†
Soil Survey Geographic Database
provided by the Natural Resources
Conservation Service
Precipitation
• Derived from point
estimates or modeled
– OSU PRISM data
• Annual average
• Single event rainfall
Pollutants
• Pollutant coefficients
– Event mean concentrations
– Land cover specific
• Defaults
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Nitrogen
Phosphorus
Lead
Zinc
• User–definable
– New pollutants
– New coefficients
– Different criteria
Outputs
• Runoff volume
• Accumulated runoff
• Sediment yield
• Accumulated sediment
load
• Pollutant yield
• Accumulated pollutant
load
• Pollutant concentration
Baseline Runoff
• Flow directions derived
from topography
• Precipitation grid
provides amount of
rainfall
• Uses soils and land cover
data to estimate volume
of runoff
• Validated
Baseline Erosion
• Estimates total annual
sediment load delivered to
coast
• Provides a conservative
estimate
– A “worst-case” scenario
Baseline Nitrogen
• Estimates total annual
pollutant load delivered
to coast
• Focuses attention on
source areas
Baseline Nitrogen
• Estimates total annual
pollutant concentration
• Focuses attention on
source areas
Example Application
• Makaha Valley, Oahu,
Hawaii
• Annual time scale
• “What-if” scenario
1. Baseline
2. Land cover change
• New residential
development
3. Climate change
• Change in rainfall
characteristics
Land Cover Change Scenario
• Develop a subdivision
• Change scrub/shrub
vegetation to low
intensity development
Nitrogen (Pre-Change)
• Baseline
– Low nitrogen runoff
• Add scenario
Nitrogen (Post-Change)
• Compare baseline
estimate to the new
estimated load
• 138 percent increase in
annual nitrogen load
Climate Change
Scenarios
• Same amount of rainfall,
but change the number
and intensity of the
storms
– 7 raining days, Type I
– 14 raining days, Type IA
– 3 raining days, Type II
Questions?
Download OpenNSPECT:
nspect.codeplex.com
Esri 9.x version at
csc.noaa.gov/nspect
Project Contacts:
Dave Eslinger, Project lead
Dave.Eslinger@noaa.gov
843-740-1270
Shan Burkhalter
Shan.Burkhalter@noaa.gov
843-740-1275
Matt Pendleton
Matt.Pendleton@noaa.gov
843-740-1196