Coastal Water Quality Tool
Overview of N-SPECT
The Nonpoint-Source Pollution and Erosion Comparison Tool (N-SPECT) examines the relationships between land cover, soil characteristics, topography, and precipitation in order to assess spatial patterns of surface water runoff, nonpoint source pollution, and erosion. N-SPECT is a geographic information systems (GIS) tool implemented in Environmental Systems Research Institute® (ESRI) ArcGIS™ software (versions 8.3 and 9.x) and requires the Spatial Analyst™ extension.
Land cover, topography, soils, and precipitation data sets are used to estimate rainfall runoff volume as well as suspended sediment concentrations and total loads at both the local (pixel) and watershed scales. Coefficients representing the contribution of each land cover class to observed pollutant concentrations are applied to the land cover data set to approximate pollutant loads and concentrations. For use in the Wai‘anae region, the default coefficients provided with N-SPECT were derived from published studies and local water quality sampling data. For each pollutant analyzed, water quality ratings are assigned spatially by comparing pollutant concentrations calculated by N-SPECT to user-defined water quality standards. Such results can help resource managers and planners target areas needing attention.
N-SPECT also allows users to compare current land cover conditions to hypothetical changes in both land use and land cover. The results of N-SPECT analyses are intended to be used as screening tools to help understand and predict the impacts of management decisions on water quality and, potentially, on coastal ecological receptors, such as corals.
Accessing the Tool
N-SPECT is available for download from the National Oceanic and Atmospheric Administration (NOAA) Coastal Services Center's Web site at http://www.csc.noaa.gov/nspect. Detailed installation instructions for N-SPECT can be found on the Web site for use with ESRI's ArcGIS version 8.3 or 9.x software. Note the Spatial Analyst extension is also required.
Documentation is provided with N-SPECT that describes how to operate the tool, how and where to access example data, and how the tool performs the analyses. The documentation, which are part of the setup.exe file, include
- on-line Help files, which can be accessed when using N-SPECT in ArcMap from the main N-SPECT menu;
- a Tutorial, which provides step-by-step instructions on how to perform various analyses in N-SPECT;
- a User's Manual, which provides a detailed discussion of the interfaces within N-SPECT and the data required to perform an analysis; and
- a Technical Guide, which explains in detail where the data were acquired for the Wai'anae study area and how the data were processed to be compatible with N-SPECT. The technical guide also walks a user through the basic operation of N-SPECT and explores advanced analysis options through the applications of different land use and land management scenarios.
