U.S. Department of the Interior

U.S. Geological Survey

 Fact Sheet 2006–3088

Revised September 2008

“HIP” New Software: 

The Hydroecological Integrity Assessment Process

Printed on recycled paper

Linking Streamflow and Stream Health

Managing rivers and streams to maintain healthy aquatic 

ecosystems is a challenge for resource managers across the 

country. Demand for competing uses of water resources grows 

with escalating development, increasing recreational use, and 

the vagaries of climate and weather. For many species of concern, instream flow and associated water quality are critical for 

survival. Balancing ecosystem needs with proposed changes in 

flow regimes requires a process managers can use to determine 

the ecological and hydrological effects of changes in streamflow.

In response, scientists at the USGS Fort Collins Science 

Center (FORT) have developed the Hydroecological Integrity 

Assessment Process (HIP) and a suite of software tools for 

conducting a hydrologic classification of streams, addressing 

instream flow needs, and assessing past and proposed hydrologic alterations on streamflow and other ecosystem components. The HIP recognizes that streamflow is strongly related 

to many critical physiochemical components of rivers, such 

as dissolved oxygen, channel geomorphology, and habitats. 

Streamflow is considered a “master variable” that limits the 

distribution, abundance, and diversity of many aquatic plant and 

animal species.

The HIP is intended for use by Federal and State agencies, 

institutions, private firms, and nongovernmental entities that 

have responsibility for or interest in managing and (or) regulating streams to maintain or restore ecological integrity. In addition, the HIP can assist managers and researchers by identifying 

ecologically relevant, stream-class-specific hydrologic indices 

that adequately characterize the five major components of the 

flow regime (magnitude, frequency, duration, timing, and rate 

of change) by using 10 nonredundant indices. The process is 

developed at a State or other large geographical area scale but 

applied at the stream reach level (fig. 1). 

To date, the software tools have been specifically developed 

for the State of New Jersey and are in development for several 

additional States, including Missouri and Massachusetts. 

The “HIP” Options

Three options are available to resource managers and scientists depending on your specific needs: (1) develop the HIP for 

a State or region, (2) apply the National Hydrologic Assessment 

Tool, or (3) apply the state-specific New Jersey HIP-derived tools.

Develop the Hydroecological Integrity Assessment Process (HIP)

If you wish to develop a HIP for your State or region, FORT 

scientists will work with you to classify your streams and build 

customized State-specific software. To learn more about the 

HIP, download and read the Users’ Manual for the Hydrological Integrity Assessment Process Software and “Redundancy 

and the choice of hydrologic indices for characterizing streamflow regimes” by Olden and Poff (2003) (see Web References, 

next page). The introduction in the Users’ Manual explains 

the purpose of the Hydrologic Index Tool (HIT), which calculates 171 ecologically relevant hydrologic indices using daily 

and peak flow records. The indices are then used for a State 

or regional stream classification analysis. If you’re interested 

in developing a customized HIP, contact USGS scientist Jim 

Henriksen at FORT (see For More Information, next page).

The Green River in Dinosaur National Monument, Utah. Photo by Doug 

Andersen/USGS. 

Photo courtesy of New Jersey Department of Environmental Protection.
Apply the National Hydrologic Assessment Tool (NATHAT)

NATHAT is stand-alone software that requires the user 

to assign a stream class to a river or stream reach of interest based on a national stream classification (using six stream 

types), as described in “A hydrogeography of unregulated 

streams in the United States and an examination of scaledependence in some hydrological descriptors” (Poff, 1996). 

Although helpful, this national classification is less refined 

than classifications developed through the HIP at the State or 

regional level. For example, the national classification identified 

only two stream types in New Jersey, but the New Jersey-specific stream classification identified four stream types. Federal 

agencies involved in water management issues (such as the U.S. 

Fish and Wildlife Service, the Bureau of Reclamation, and the 

Army Corps of Engineers) will find the National Hydrologic 

Assessment Tool of particular value for quantifying the extent 

of hydrologic alteration.

Apply the New Jersey Tools (NJHAT and NJSCT) 

Managers in the State of New Jersey can apply the State-specific software tools using the New Jersey Hydrologic Assessment Tool (NJHAT) and the New Jersey Stream Classification 

Tool (NJSCT) for unclassified stream and river reaches. Also, 

managers considering development of a customized HIP for 

their State or area of interest can compare the benefits of the 

customized NJHAT with NATHAT.

For More Information

To discuss development of a HIP for your State or 

geographic area of interest, or for more information 

about the process and software tools, contact: 

Brian Cade

U.S. Geological Survey 

Fort Collins Science Center

2150 Centre Ave., Bldg. C

Fort Collins, CO 80526-8118

Tel: 970.226.9326

Fax: 970.226.9230

E-mail: cadeb@usgs.gov

Web Resources

 Users’ Manual for the Hydrological Integrity Assessment Process Software (Open-File Report 2006-1093). Available at 

 http://www.fort.usgs.gov/products/publications/21598/21598.asp

 National Hydrologic Assessment Tool (NATHAT). Available at 

 http://www.fort.usgs.gov/Products/Software/NATHAT/

 New Jersey Hydrologic Assessment Tool (includes the NJSCT). Available at 

 http://www.fort.usgs.gov/Products/Software/NJHAT/

 Poff, N.L. 1996. A hydrogeography of unregulated streams in the United States and an examination of scale-depen 

dence in some hydrological descriptors. Freshwater Biology 36:71-91. Available at 

 http://rydberg.biology.colostate.edu/poffpubs/Poff1996(FWB_hydrogeogr).pdf 

 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. Available at 

 http://rydberg.biology.colostate.edu/poffpubs/Olden2003(RRM_Hydrol_Index).pdf 

Figure 1. Steps involved in developing and applying the Hydroecological 

Integrity Assessment Process (HIP).