An open source version of the Nonpoint Source

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 Open. NSPECT? • 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 – – 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* – – – 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 – – 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 • Validated ct di re Fl ow • Uses soils and land cover data to estimate volume of runoff io n • Precipitation grid provides amount of rainfall

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 Open. NSPECT: nspect. codeplex. com Esri 9. x version at csc. noaa. gov/nspect Project Contacts: Dave Eslinger, Project lead Dave. [email protected] gov 843 -740 -1270 Shan Burkhalter Shan. [email protected] gov 843 -740 -1275 Matt Pendleton Matt. [email protected] gov 843 -740 -1196