Jong, In some work I was doing today I think I stumbled across a more reliable layer that shows Nitrogen and Phosphorus impairments. It was put together by the EPA. It used a slightly different method to come up with the layer than I used. … I haven’t been able to see the actual GIS layer, but I think maybe this one might be better…. I’m sorry to change course after the work you’ve done. Let me know if you have any thoughts.
You can find it at this link, and it’s the row called “Waters Listed for N/P Impairments”
https://gispub2.epa.gov/NPDAT/DataDownloads.html
Ike, there is also a link in that row, it says “HTML” and it gives some background on how they selected this subset of the listed waters.
There are a couple more layers on this page that I’d like to include on the site, such as “Mississippi-Atchafalaya River Basin Boundary”, and the “SPARROW N / P yields.”
Thanks,
Ted
The data has been downloaded and stored at box shared, gltg-source-data\impaired-water-epa
The csv file needs to be joined with shapefile.
From the CSV file, we found the following categories of cause of impairment. We need to decide which one to map