National Hydrologic Assessment Tool (NATHAT)

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). 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.

Figure 1. Steps for applying the National Hydrologic Assessment Tool.

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

1. download and read both articles,

2. download and read the Users’ Manual for the Hydroecological Integrity Assessment Process Software, and

3. download the software.

For questions concerning the use of NATHAT, contact:

Jim Henriksen
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: jim_henriksen@usgs.gov

Also at FORT

• Users’ Manual for the Hydroecological Integrity Assessment Process Software
• “HIP” New Software: The Hydroecological Integrity Assessment Process
• New Jersey Hydrologic Assessment Tools (NJHAT and NJSCT)

Related Resources

• Peer-reviewed publications of N.L. Poff (and J.D. Olden)
  • A hydrogeography of unregulated streams in the United States and an examination of scale-dependence in some hydrological descriptors
  • Redundancy and the choice of hydrologic indices for characterizing streamflow regimes