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I'm working on a web map using esri arcgis javascript api. I'd like to use the NHD Watershed Boundary Data to draw polygons based on the boundaries of the watersheds.

Does anyone have any ideas of how to start?

I've looked at the National Map where I can download data but ideally, I could pull data from an online source rather than hosting it myself where I would be responsible for any changes to the data. I'm already using the NHD Watershed Basemap as my basemap but I don't see where the watershed boundaries are available.

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This API link from EPA shows the Watersheds http://watersgeo.epa.gov/arcgis/rest/services/NHDPlus_NP21/WBD_NP21_Simplified/MapServer?f=jsapi -

raw http://watersgeo.epa.gov/arcgis/rest/services/NHDPlus_NP21/WBD_NP21_Simplified/MapServer/export?dpi=96&transparent=true&format=png8&bbox=-8700899.515789473%2C4690058%2C-8450228.484210527%2C4715020&bboxSR=102100&imageSR=102100&size=1908%2C190&f=image

Firebug for Firefox (Chrome Developer tools can do the same) it traces the map applications network traffic and source urls.

You might have to request permission to use this as it does not seem to be a public known mapservice.

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It looks like you found the service to use ... http://watersgeo.epa.gov/arcgis/rest/services/NHDPlus_NP21/WBD_NP21_Simplified/MapServer/

Just plug that in to one of the many samples available and start from there.

Go Here and click "Browse Samples" https://developers.arcgis.com/javascript/

Find one that does something similar to what you want to do (or find 2 or three).

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I don't work with APIs am not exactly sure what you are looking for, but watershed boundary data is available and downloadable as polygon shapefiles from multiple websites.

For example, ftp://ftp.ftw.nrcs.usda.gov/wbd/ allows one to download maps at different watershed (HUC) scales.

When you say "watershed boundary" you also need to specify at what scale.

This site provides more information regarding hydrologic units, etc.

http://water.usgs.gov/GIS/huc.html

Is this the answer you were looking for?

  • I would like multiple scales since users will be zooming in and out. I am also looking for live data as opposed to downloadable data so I don't have to host it or keep it updated. I have downloaded watershed data that I'm currently looking at. – daniella Jul 29 '14 at 19:52

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