| description:
|
HUC12s in this layer intersect Forest System boundaries
WBD data sources:
-Non-Alaska – ‘WBD_Poly_Seamless.xml’ included in ‘Metadata’ folder
-Alaska – ‘WBD_National_GDB.xml’ included in ‘Metadata’ folder
SPA description:
SPAs developed using NHDPlus V2.1 simplified catchments. Source Protection Area (SPA) polygons composed of all NHDPlus catchments located one day's time of travel (24 hours) upstream from inland water surface facility point events related to surface water drinking water system facilities from a SDWIS/FED extract for 2017, georeferenced to initialized inland NHD medium resolution flowlines.
NHDPlus v2.1 does not include catchments for Alaska, therefore no SPAs have been developed.
Area Calculation description:
‘Percentage of HUC12 covered by SPAs’ is calculated using the US area of the HUC12 and SPA features. The HUC12s are further clipped using the processing extent of the NHDPlus V2.1. This ensures that all HUC12 features are covered by NHDPlus V2 catchments, notably in coastal areas where the HUC12s extend into the ocean.
Catchment data source:
- ‘NHDPlusV2_metadata.xml’ included in ‘Metadata’ folder |