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 is critical for survival. Balancing these ecosystem needs with proposed changes in flow regimes requires a process managers can use to classify streams and determine the ecological and hydrological impacts of changes in streamflow.
In response, USGS scientists 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/or 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 water temperature, and can be considered a “master variable” that limits the disturbance, abundance, and diversity of many aquatic plant and animal species.
Figure 1. Steps taken to develop and apply the regional Hydroecological Integrity Assessment Process (HIP).
The HIP is intended for use by any federal or state agency, institution, private firm, or nongovernmental entity that has responsibility for or interest in managing and/or regulating streams to restore or maintain ecological integrity. In addition, the HIP can assist researchers by identifying ecologically relevant, stream-class-specific hydrologic indices that adequately characterize the 5 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 is applied at the stream-reach level (Figure 1).
To date, the HIP has been fully developed for the State of New Jersey and is in development for several additional states, including Missouri and Massachusetts. Among the set of tools, 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.
Three options are available for developing or applying the HIP tools to streams in your state or region. Which you select depends on your particular needs and objectives, as described below:
Develop the Hydroecological Integrity Assessment Process (HIP)– If you wish to apply HIP in your state or region, FORT scientists will work with you to classify your streams and build the customized HIP software. To learn more about the HIP as well as the Hydrologic Index Tool (HIT), used during the stream-classification analysis, download and read the Users’ Manual for the Hydroecological Integrity Assessment Process Software (Open-File Report 2006-1093) and “Redundancy and the choice of hydrologic indices for characterizing streamflow regimes,” by Olden and Poff (2003). The introduction in the Users’ Manual explains the purpose of the 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. To discuss the development of the HIP for your state or region, contact Brian Cade at the USGS Fort Collins Science Center.
Apply the National Hydrologic Assessment Tool (NATHAT) – NATHAT requires managers to make a determination of a general stream classification for a river or stream reach of interest based on a national stream classification (using 6 stream types) as described in “A hydrogeography of unregulated streams in the United States and an examination of scale-dependence in some hydrological descriptors” (Poff, 1996). While helpful, this national classification is less refined than classifications developed through HIP at the state or regional level. For example, the national classification identified two stream types in New Jersey, but the New Jersey-specific stream classification completed as part of the HIP for that state identified four stream types.
Apply the New Jersey Tools – Managers in the state of New Jersey can apply the New Jersey Hydrologic Assessment Tool (NJHAT) and the New Jersey Stream Classification Tool (NJSCT) for as-yet 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.
To discuss the development of a HIP for your state or geographic area of interest, or for more information about the process and software tools, contact: