Problem

Figure 1. Diagram shows relation among five stream components. Solid lines indicate a strong influence and dashed lines indicate a weak or smaller influence. Hydrologic factors play a substantial role in determining the biological health of a stream.

The population of New Jersey has grown from about 5 million people in 1950 to 8.1 million people in 2000. As the population has increased, stresses on the State's water resources also have increased. The population increase and the associated development have necessitated an increase in the withdrawals of both surface and ground water to meet water-supply demands, have increased the amount of wastewater discharged from treatment facilities, and have increased the amount of impervious surface area and resulting stormwater flows. These anthropogenic effects have modified the magnitude of streamflow in many streams throughout the State. Several studies indicate that streamflow alterations can greatly affect fish and benthic communities (figure 1).

There are many competing demands on the water resources of the State of New Jersey. The New Jersey Department of Environmental Protection (NJDEP) is responsible through various permit and planning programs for protecting, maintaining, and where necessary, improving streamwater quality to meet standards, preserve and enhance aquatic and land habitats, and meet the water-supply needs of the State (figure 2). One of the regulatory tools that the NJDEP uses to manage the water resources of the State is to establish passing-flow requirements as part of some permits. NJDEP passing flow requirements typically are based on the 7-day, 10-year low flow. The NJDEP is interested in developing a methodology to establish in-stream flow requirements that would improve protection of the aquatic ecosystem, use easily accessible data, and be easy to implement. This project will address this need.

Figure 2. Resource management goals in establishing minimum passing flows are to sustain and enhance the aquatic resources of streams.

Objective

The objective of the Ecological Flow Goals phase of the project is to develop a methodology to estimate flows that would sustain healthy stream ecology. The NJDEP will use the method as the technical basis for decisions (planning and regulatory) that affect streamflow and freshwater aquatic resources. The development of implementation strategies and site-specific flow criteria are the sole responsibility of the NJDEP. The project is a cooperative venture of the USGS, New Jersey District; NJDEP; and the USGS Biological Resources Discipline office located in Fort Collins, Colorado. A technical advisory committee provides direction to the project team and reviews interim outputs.

Products of this project will include software that can be used to determine streamflow indices and the effects of hydrologic modifications to the drainage basin on those indices and a final U. S. Geological Survey Scientific Investigations Report.

Two complementary projects are underway that will support the results of this study. As part of the Watershed Indicators project, the USGS is evaluating relations between aquatic ecosystem impairment and major environmental controlling factors. Results of the project will assist the NJDEP in defining stream-restoration goals that translate into viable management strategies. In the second project, Evaluating the Effects of Anthropogenically Modified Landscapes on Catchment Hydrology and Water Availability Using a Basin-Specific Flow-Modeling Tool, a model will be developed that can be used to construct streamflow hydrographs for ungaged sites on the basis of historical precipitation data. The model also can be used to determine the potential effect of future development on streamflow.

For additional information contact:

Steven Nieswand, (609) 771-3970
Jonathan Kennen, (609) 771-3948
James Henriksen, (970)-226-9324