GSDA:Obtaining Hydrographic Data from the USGS / EPA

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The National Hydrography Dataset (NHD) offers Arc/Info workspaces of hydrologic Cataloging Units and their accompanying data. The NHD Interactive Map website can be found at http://edcnts14.cr.usgs.gov/Website/nhdserver/Run.htm. If this link does not work, follow the bulletted steps below:

• Go to the USGS home page at www.usgs.gov.
• Choose the Water button near the top.
• Under the "Water Data" heading, click on the GIS link.
• Click on the NATIONAL HYDROGRAPHY DATA SET link.
• Choose the Data button at the left.
• Select the Obtaining NHD Data link.

You will now see a map of the United States and Puerto Rico. To the left of the map window are the tools to help you in navigating and selecting your data. Below the map window is a text string that displays the current, or active tool.

The United States is divided into cataloging units (CU). You can interactively click on the map to zoom to a region of interest. You can also control the zoom factor (e.g., 2x, 4x). The CUs are classified as (1) CU Distributable, (2) CU Distributable * Initial Release, and (3) CU in Progress. You will not be able to download a CU in Progress. As you zoom in, the individual CUs with their number are displayed (see image below).

Zoom in on the map so that you can distinguish individual CUs. At this point you can now do two things:

• Check the CU Identify option and then select a CU with your mouse to view the metadata (i.e., data about the data) for that specific CU.
• Check the CU Download option to begin downloading the hydrographic data for that specific CU.

1. For example, check the CU Download option and click on any CU.
2. You will be required to enter your name, but all other information is optional. A pre-download screen will appear and may take a few minutes to begin the download process.
3. If you get a security window, click on the Grant button to continue.
4. You will now get the choice to download ESRI/ARC or USGS/STDS data.
5. For example, choose the ESRI/ARC option and click the Download button to begin the download process.
6. After the CU has been saved, uncompress it with a utility such as WinZip. Click here for help on uncompressing files. The NHD data can then be brought into a GIS such as ArcView (see image below).