Layer: Predicted Background Conductivity (ID:0)

View In: Map Viewer

Name: Predicted Background Conductivity

Display Field: StreamName

Type: Feature Layer

Geometry Type: esriGeometryPolyline

Is View: true

Is Updatable View: true

Source Schema Changes Allowed: true

Sources

Description: The information displayed is based on specific conductivity predictions for stream segments in the contiguous United States from the Predicted Background Conductivity (PBC) model. The PBC model was developed using a random forest modeling approach and enables comparison with measured in-stream conductivity. Geology, soil, vegetation, climate and other empirically measured data were used as inputs. The PBC model was designed for streams with natural background SC < 2000 µS/cm. Above this level (typical for freshwater), PBC model estimates may be less reliable. Data for some parameters that affect background SC were not readily available and were therefore not included in the model. These include freshwater and marine interfaces, natural mineral springs, salt deposits which may affect groundwater and streams, and other natural sources of salts. In such areas, the model is likely to underestimate background SC, but in some arid areas the model may need to be calibrated by as much as 300 µS/cm (See Model validation below). Local knowledge is often necessary to assess differences between predicted and measured background SC. More information about the model and datasets can be found at <a href="https://epa.maps.arcgis.com/home/item.html?id=13fe4698f35d4a95ba9dfe6f8033f735" style="color:rgb(0, 121, 193); text-decoration-line:none; font-family:inherit; font-size:large;">Freshwater Explorer Metadata</a>. General Modeling ApproachThe <a href="https://github.com/USEPA/StreamCat" style="color:rgb(0, 121, 193); text-decoration-line:none; font-family:inherit;" target="_blank">StreamCat dataset</a> and process was used to develop stream-specific model predictions (Hill et al. 2016) based on watershed averages for each NHD+ segment in the contiguous United States (McKay et al. 2012). These stream segments drain an average area of 3.1 square kilometers which characterizes the spatial grain size of this dataset. Natural background SC was not estimated for streams shown as grey lines. The empirical background conductivity model was developed using the following steps: <ol><li>Create training and validation data sets of SC observations from minimally altered stream segments.</li><li>Characterize temporally and spatially specific watershed environments for each observation, including antecedent</li><li>conditions.</li><li>Relate observed SC to environmental predictors using a machine learning technique (random forests).</li><li>Assess model performance and validate using multiple observations made at randomly chosen stream segments.</li></ol>For a detailed description of the step used to develop the PBC model, see Olson and Cormier, 2019.<div style="font-family:"Avenir Next W01", "Avenir Next W00", "Avenir Next", Avenir, "Helvetica Neue", sans-serif; font-size:16px;"> Training and Validation DataThe training and validation datasets consist of minimally disturbed sites. More than 2.4 million SC observations were obtained from the Water Quality Portal (WQP) (USEPA 2016b), state natural resource agencies, the U.S. Geological Survey (USGS) National Water Information System (NWIS) system (USGS 2016), and data used in Olson and Hawkins (2012). Data were downloaded from the <a href="https://www.waterqualitydata.us/" style="color:rgb(0, 121, 193); text-decoration-line:none; font-family:inherit;" target="_blank">WQP website</a> using the following query criteria: <ul><li>Country - United States.</li><li>Sample Media - Water.</li><li>Characteristics - Conductivity, Specific Conductivity, Specific Conductance, Calculated/Measured Ratio. </li><li>Date range - observations between 1 January 2001 and 31 December 2015. This time period was chosen so that <a href="https://modis.gsfc.nasa.gov/data/" style="color:rgb(0, 121, 193); text-decoration-line:none; font-family:inherit;" target="_blank">Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data</a> (NASA 2019) could be used as predictors in the model. </li></ul> During development, 56 potential explanatory parameters were evaluated. The original source data and final datasets are available for download <a href="https://doi.org/10.23719/1500945" style="color:rgb(0, 121, 193); text-decoration-line:none; font-family:inherit;" target="_blank">here</a>. Predicted Background Conductivity metadata and data are also available on the Geoplatform. Each observation was related to the nearest stream segment in the NHD+. Data were limited to one observation per stream segment per month. SC observations with ambiguous locations and repeat measurements along a stream segment in the same month were discarded. Using estimates of anthropocentric stress derived from the StreamCat database (Hill et al. 2016), segments were selected with minimal amounts of human activity (Stoddard et al. 2006) using criteria developed for each Level II Ecoregion (Omernik and Griffith 2014). Stream segments were considered as minimally stressed when the associated watershed drainage area had ≤0.5% impervious surface, ≤5% urban, ≤10% agriculture, and population densities of 0.8 to 30 people per square kilometer. Watersheds displaying large residuals during initial model predictions were assessed for evidence of other human activities not represented in StreamCat (e.g., mining, logging, grazing, or oil/gas extraction). Disturbed watersheds with a tidal influence or unusual geologic conditions, such as hot springs, were not removed from the dataset. Some sites with high levels remain in the dataset (e.g., mining influenced but no easily accessible evidence). Some sites with high SC remain in the dataset (e.g., mining influenced but no national record). About 5% of SC observations in each National Rivers and Stream Assessment (NRSA) region were then randomly selected as independent validation data. The remaining observational dataset was used for model calibration. The final training data set used for modeling had 1785 stream segments with 11 796 observations, and the validation data set had 92 segments with 581 observations. The majority of segments had a single observation but ranged up to 165 observations per segment. Model ValidationThe "Model Validation" view on the Freshwater Explorer shows the predictive performance at reference sites that were used to develop PBC model. In the wetter and more forested areas, reference sites were more abundant and predictions are more precise. In the central U.S., fewer reference sites were available and predictions are more uncertain. In the grass and shrub lands east of the continental divide, measured SC was over-predicted by the model by more than 100 µS/cm at 5% of sites (yellow dots) and under-predicted by more than 100 µS/cm at 3% of sites (red dots). Calculated differences between measured and predicted SC are reported as residuals in pop-up boxes on this view. There are many potential causes for these differences, including data reporting errors and reference site reliability. Overall, the model explained most of the variation in SC and produced reasonably accurate predictions for both calibration data (Mean Absolute Error = 22 µS/cm, Nash-Sutcliffe Efficiency = 0.92, and Coefficient of Determination = 0.92) and external validation data (Mean Absolute Error = 29 µS/cm, Nash-Sutcliffe Efficiency = 0.87, and Coefficient of Determination = 0.87). Values reported as background only apply to streams and have not been validated for lakes or wetlands. More details can be found in Olson and Cormier (2019). References<ul><li>Hill, R.A., Weber, M.H., Leibowitz, M.H., Olsen, A.R., Thornbrugh, D.J., 2016. The Stream-Catchment (StreamCat) Dataset: A Database of Watershed Metrics for the Conterminous United States. JAWRA Journal of the American Water Resources Association, 52(1), 120-128. doi: <a href="https://doi.org/10.1111/1752-1688.12372" style="color:rgb(0, 121, 193); text-decoration-line:none; font-family:inherit;" target="_blank">https://doi.org/10.1111/1752-1688.12372</a></li><li>McKay, L., Bondelid, T., Dewald, T., Johnston, J., Moore, R., Rea, A., 2012. NHDPlus Version 2: User Guide. National Operational Hydrologic Remote Sensing Center, Washington, DC. Available at: <a href="https://epa.maps.arcgis.com/home/item.html?id=540abb1d015b4bd2b87d30f4c28a58cb&view=table" style="color:rgb(0, 121, 193); text-decoration-line:none; font-family:inherit;" target="_blank">https://nctc.fws.gov/courses/references/tutorials/geospatial/CSP7306/Readings/NHDPlusV2_User_Guide.pdf</a></li><li>NASA, 2019. Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. Available at: <a href="https://epa.maps.arcgis.com/home/item.html?id=540abb1d015b4bd2b87d30f4c28a58cb&view=table" style="color:rgb(0, 121, 193); text-decoration-line:none; font-family:inherit;" target="_blank">https://modis.gsfc.nasa.gov/data/</a></li><li>Olson, J.R., Hawkins, C.P., 2012. Predicting natural base‐flow stream water chemistry in the western United States. Water Resources Research, 48(2). doi: <a href="https://epa.maps.arcgis.com/home/item.html?id=540abb1d015b4bd2b87d30f4c28a58cb&view=table" style="color:rgb(0, 121, 193); text-decoration-line:none; font-family:inherit;" target="_blank">https://doi.org/10.1029/2011WR011088</a></li><li>Olson, J.R. and Cormier, S.M., 2019. Modeling spatial and temporal variation in natural background specific conductivity. Environmental Science and Technology. doi: <a href="https://epa.maps.arcgis.com/home/item.html?id=540abb1d015b4bd2b87d30f4c28a58cb&view=table" style="color:rgb(0, 121, 193); text-decoration-line:none; font-family:inherit;" target="_blank">https://dx.doi.org/10.1021/acs.est.8b0677</a>7</li><li>Olson, J.R. and Cormier, S.M., 2019. Modeling spatial and temporal variation in natural background specific conductivity: Data sets and R-code. doi: <a href="https://doi.org/10.23719/1500945" style="color:rgb(0, 121, 193); text-decoration-line:none; font-family:inherit;" target="_blank">https://doi.org/010.23719/1500945</a></li><li>Omernik, J. M.; Griffith, G. E., 2014. Ecoregions of the conterminous United States: evolution of a hierarchical spatial framework. Environmental. Management. 54 (6), 1249−1266. doi: <a style="color:rgb(0, 121, 193); font-family:inherit;" target="_blank">https://doi.org/10.1007/s00267-014-0364-1</a></li><li>U.S. Environmental Protection Agency (U.S. EPA), 2016. STORET. Available at: <a href="https://epa.maps.arcgis.com/home/item.html?id=540abb1d015b4bd2b87d30f4c28a58cb&view=table" style="color:rgb(0, 121, 193); text-decoration-line:none; font-family:inherit;" target="_blank">https://www.epa.gov/storet/</a></li><li>U.S. Geological Survey (USGS), 2016. National Water Information System. Available at: <a href="https://epa.maps.arcgis.com/home/item.html?id=540abb1d015b4bd2b87d30f4c28a58cb&view=table" style="color:rgb(0, 121, 193); text-decoration-line:none; font-family:inherit;" target="_blank">https://waterdata.usgs.gov/nwis</a></li><li>Stoddard, J. L., Larsen, D. P., Hawkins, C. P., Johnson, R. K., Norris, R. H., 2006. Setting expectations for the ecological condition of streams: the concept of reference condition. Ecol. Appl. 2006, 16 (4), 1267−1276. doi: <a href="https://doi.org/10.1890/1051-0761(2006)016[1267:SEFTEC]2.0.CO;2" style="color:rgb(0, 121, 193); text-decoration-line:none; font-family:inherit;" target="_blank">https://doi.org/10.1890/1051-0761(2006)016[1267:SEFTEC]2.0.CO;2</a></li></ul></div>

Copyright Text: John O. Olson, Christopher L. Wharton, Susan M. Cormier

Min. Scale: 1879005

Max. Scale: 0

Default Visibility: true

Max Record Count: 1000

Supported query Formats: JSON, geoJSON, PBF

Use Standardized Queries: True

Extent:

Drawing Info:

{"renderer":{"authoringInfo":{"type":"classedColor","classificationMethod":"esriClassifyManual"},"type":"classBreaks","field":"AvgPredEC","legendOptions":{"order":"ascendingValues"},"minValue":10.293370165745854,"classBreakInfos":[{"symbol":{"color":[115,0,76,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":25,"label":"0 - 25"},{"symbol":{"color":[112,35,90,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":50,"label":"25 - 50"},{"symbol":{"color":[110,56,107,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":75,"label":"50 - 75"},{"symbol":{"color":[104,75,125,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":100,"label":"75 - 100"},{"symbol":{"color":[94,93,143,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":125,"label":"100 - 125"},{"symbol":{"color":[82,113,163,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":150,"label":"125 - 150"},{"symbol":{"color":[61,132,184,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":200,"label":"150 - 200"},{"symbol":{"color":[55,149,196,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":250,"label":"200 - 250"},{"symbol":{"color":[96,163,181,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":300,"label":"250 - 300"},{"symbol":{"color":[130,179,169,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":350,"label":"300 - 350"},{"symbol":{"color":[160,194,155,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":400,"label":"350 - 400"},{"symbol":{"color":[187,209,138,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":450,"label":"400 - 450"},{"symbol":{"color":[215,227,125,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":500,"label":"450 - 500"},{"symbol":{"color":[243,245,108,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":550,"label":"500 - 550"},{"symbol":{"color":[252,231,91,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":600,"label":"550 - 600"},{"symbol":{"color":[252,196,76,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":650,"label":"600 - 650"},{"symbol":{"color":[252,164,63,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":700,"label":"650 - 700"},{"symbol":{"color":[250,133,50,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":800,"label":"700 - 800"},{"symbol":{"color":[245,99,37,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":900,"label":"800 - 900"},{"symbol":{"color":[240,67,29,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":1000,"label":"900 - 1000"},{"symbol":{"color":[232,16,20,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":1500,"label":"1000- 1500"},{"symbol":{"color":[173,16,20,255],"width":1.7499999999999998,"type":"esriSLS","style":"esriSLSSolid"},"classMaxValue":5000,"label":"1500 - 5000"}],"classificationMethod":"esriClassifyManual"},"transparency":0}
HasZ: true

HasM: true

Has Attachments: false

Has Geometry Properties: true

HTML Popup Type: esriServerHTMLPopupTypeAsHTMLText

Object ID Field: OBJECTID

Unique ID Field:

Global ID Field: GlobalID

Type ID Field:

Fields:

OBJECTID (type: esriFieldTypeOID, alias: OBJECTID, SQL Type: sqlTypeOther, length: 0, nullable: false, editable: false)
COMID (type: esriFieldTypeInteger, alias: COMID, SQL Type: sqlTypeOther, nullable: true, editable: true)
StreamName (type: esriFieldTypeString, alias: StreamName, SQL Type: sqlTypeOther, length: 65, nullable: true, editable: true)
AvgPredEC (type: esriFieldTypeDouble, alias: Conductivity (µS/cm), SQL Type: sqlTypeOther, nullable: true, editable: true)
F50Pct_PL (type: esriFieldTypeDouble, alias: Conductivity (µS/cm), SQL Type: sqlTypeOther, nullable: true, editable: true)
FTYPE (type: esriFieldTypeString, alias: Stream Type, SQL Type: sqlTypeOther, length: 24, nullable: true, editable: true)
FCODE (type: esriFieldTypeInteger, alias: FCODE, SQL Type: sqlTypeOther, nullable: true, editable: true)
GlobalID (type: esriFieldTypeGlobalID, alias: GlobalID, SQL Type: sqlTypeOther, length: 38, nullable: false, editable: false)
Shape__Length (type: esriFieldTypeDouble, alias: Shape__Length, SQL Type: sqlTypeDouble, nullable: true, editable: false)

Templates:

Is Data Versioned: false

Has Contingent Values: false

Supports Rollback On Failure Parameter: true

Last Edit Date: 5/24/2023 3:24:46 PM

Schema Last Edit Date: 5/24/2023 3:24:46 PM

Data Last Edit Date: 7/27/2021 1:55:52 PM

Supported Operations: Query Query Top Features Query Analytic Query Bins Generate Renderer Validate SQL Get Estimates ConvertFormat