National Hydrologic Assessment Tool (NATHAT)

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The National Hydrologic Assessment Tool (NATHAT) is based on a hydrologic classification of streams by Poff (1996) involving 420 gaging stations across the contiguous United States (Figure 1). The Hydrologic Index Tool (HIT) is available for batch processing of multiple USGS gauge records to compute the 171 hydroecological indices for specified periods of record. If you have daily and peak (optional) streamflow data for a period of record, you can use NATHAT to

1. establish a hydrologic baseline (reference time period),

2. establish environmental flow standards, and

3. evaluate past and proposed hydrologic modifications.

Six stream classes are available in NATHAT. However, a national stream classification tool is not available. Therefore, the user must make an informed decision as to which stream type is being examined using the information in articles by Poff (1996) and Olden and Poff (2003) (Figure 1). To make this determination, the user should

Figure 1. Application of the National Hydrological Integrity Assessment Process.

Figure 1: Steps for applying the National Hydrologic Assessment Tool (NATHAT).

download and read both articles,
download and read the Users’ Manual for the Hydroecological Integrity Assessment Process Software,
download the NATHAT software
download the HIT software

For questions concerning the use of NATHAT, contact:

Brian Cade
U.S. Geological Survey
Fort Collins Science Center
2150 Centre Ave, Bldg c.
Fort Collins, CO 80526-8118

Tel: 970-226-9324
Fax: 970-226-9230
E-mail: cadeb@usgs.gov

Also at FORT

Related Resources

N.L. Poff [and J.D. Olden] Publications
- Olden, J.D., and N.L. Poff. 2003. Redundancy and the choice of hydrologic indices for characterizing streamflow regimes. River Research and Applications 19:101-121.
- Poff, N.L. 1996. A hydrogeography of unregulated streams in the United States and an examination of scale-dependence in some hydrological descriptors. Freshwater Biology 36:71-91.