NHD Data Availability

• The National Hydrography Dataset is now available in a new database design that allows better web-based access and query, as well as truly seamless data that can be downloaded in various extents. The new database design provides a distribution format called NHDinGEO. Data requests in NHDinGEO can be extracted by subbasin, county, congressional district or by topographic map quad. Data can be extracted in blocks encompassing several adjacent reference areas. Data are also available in a modified form of the traditional NHDinARC model called NHDGEOinARC. Data requests in NHDGEOinARC are only available by individual subbasins. An upgrade to the NHD ArcView 3.x Toolkit that is compatible with the NHDGEOinARC format is expected to be released sometime in early fall, 2004.
  
  
• Data are built on a per-request basis. Requests for NHDinGEO data will process the quickest while NHDGEOinARC requests may take several hours or even days. Once a data request is completed, you will be notified of the data availability and ftp location via e-mail. The data will remain available for 7 days.
  
  
• To check the status of NHDinGEO data please see the NHD Status layer on the NHD viewer. You can also visit EPA's Surf Your Watershed web site if you need to locate the subbasin of interest to you, or don't know the subbasin number.
  
  If you want to read more about the new NHDinGEO format, the NHDinARC to NHDinGEO transition, or the NHDGEOinARC format, please see the NHD Geodatabase page.