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Ecologically Relevant Hydrologic Indices for a Baseline Period of Record for Selected Stream Gages in New Jersey

Project Title: Data Model of Stream Flows: Baseline Identification & Analysis for the Ecological Flow Goals
Project Number: 2454C2R
Project Chief: Baker, Ronald J.
Project Staff: Esralew, Rachel A.
Period of Project: 01-JUN-2005 to 30-SEP-2007

The Hydroecological Integrity Assessment Process for New Jersey

The hydroecological integrity assessment process (HIP) has been fully developed for the State of New Jersey (NJHIP). The New Jersey Department of Environmental Protection is in the process of applying ecologically relevant ecological flow goals (ERHI's) from the NJHIP to current and future regulation of New Jersey streams, which would assist the NJDEP in incorporating ecological integrity as a regulatory management tool. NJDEP has selected specific primary and surrogate ERHI's from the NJHIP as well as additional indices that are relevant to streamflow regulation procedures.

The ERHI tables for New Jersey streams contain information about the selected gages and ERHI's, and a table of all ERHI's for the baseline period of record for selected streams gages, with references to those ERHI's that were selected by the NJHIP to optimally characterize the flow regime as well as additional ERHI's selected for regulatory use by NJDEP.

It is the goal of NJDEP to evaluate potential impacts of a proposed water withdrawal by determining the change in streamflow characteristics. Regulatory programs may be established by using critical ERHI's and percentile limits as thresholds for ecological and biological sustainability in stream systems. In order for managing agencies to adequately determine appropriate goals for establishing thresholds for ERHI's that will protectively encompass conditions where ecological integrity can be maintained, streamflow data from the basin should be selected from a period of time where the basin was the least altered by anthropogenic activities. These activities may include, but are not limited to, regulation, diversion, landscape alteration, and stream and groundwater withdrawals in the drainage basin. By using streamflow record during this baseline period to compute ERHI's and index thresholds, these thresholds can be used to establish hydroecological flow goals that researchers and managing agencies can use to guide instream flow requirements in an effort to maintain or return to streamflow conditions that protect ecological integrity.

Figure 5. Flow chart showing steps for determining baseline periods and the quality of baseline period.

The baseline period of record for selected streams were determined by the U.S. Geological Survey ( New Jersey Water Science Center, West Trenton, New Jersey, and the Fort Collins Science Center, Fort Collins, Colorado) with cooperation from the NJDEP. These baseline periods were selected based on an analysis of trends in annual streamflow variability, estimated historical landuse practices, and historical gage information. A web summary of background information on HIP and NJHIP is provided and information about the methods used to determine the baseline period of record are detailed in "Determination of Baseline Periods of Record for Selected Streamflow-Gaging Stations in New Jersey for Determining Ecologically Relevant Hydrologic Indices (ERHI)") by Esralew and Baker (2008).

Project proposal summary

For information about the NJHIP, contact:

Jonathan Kennen
New Jersey Water Science Center
E-mail: jgkennen@usgs.gov

Jeff Hoffman
New Jersey Department of Environmental Protection
E-mail: Jeffery.L.Hoffman@dep.state.nj.us

Brian Cade
Fort Collins Science Center
E-mail: cadeb@usgs.gov

Publication

Esralew, R.A.; Baker, R.J. , Determination of Baseline Periods of Record for Selected Streamflow-Gaging Stations in New Jersey for Determining Ecologically Relevant Hydrologic Indices (ERHI) : U.S. Geological Survey Scientific Investigations Report 2008-5077, 72 p.

Additional References

Henriksen, J.A, J. Heasley, J.G. Kennen, and S. Nieswand. 2006. Users' manual for the Hydroecological Integrity Assessment Process software (including the New Jersey Assessment Tools): U.S. Geological Survey, Open-File Report 2006-1093, 71 p.

Kennen, J.G.; Henriksen, J.A.; Nieswand, S.P., Development of the Hydroecological Integrity Assessment Process for Determining Environmental Flows for New Jersey Streams: U.S. Geological Survey Scientific Investigations Report 2007-5206, 56 p.

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., Allan, J.D., Bain, M.B., Karr, J.R., Prestegaard, K.L., Richter, B.D., Sparks, R.E., and Stromberg, J.C., 1997, The natural flow regime: A new paradigm for riverine conservation and restoration: BioScience, v. 47, p. 769-784.

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.