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Scientific Investigations Report 2014-5004

Prepared in cooperation with the New Jersey Department of Environmental Protection

Regional Regression Equations for the Estimation of Selected Monthly Low-Flow Duration and Frequency Statistics at Ungaged Sites on Streams in New Jersey

By Kara M. Watson and Amy R. McHugh

Thumbnail of and link to report PDF (67.1 MB)Abstract

Regional regression equations were developed for estimating monthly flow-duration and monthly low-flow frequency statistics for ungaged streams in Coastal Plain and non-coastal regions of New Jersey for baseline and current land- and water-use conditions. The equations were developed to estimate 87 different streamflow statistics, which include the monthly 99-, 90-, 85-, 75-, 50-, and 25-percentile flow-durations of the minimum 1-day daily flow; the August–September 99-, 90-, and 75-percentile minimum 1-day daily flow; and the monthly 7-day, 10-year (M7D10Y) low-flow frequency. These 87 streamflow statistics were computed for 41 continuous-record streamflow-gaging stations (streamgages) with 20 or more years of record and 167 low-flow partial-record stations in New Jersey with 10 or more streamflow measurements.

The regression analyses used to develop equations to estimate selected streamflow statistics were performed by testing the relation between flow-duration statistics and low-flow frequency statistics for 32 basin characteristics (physical characteristics, land use, surficial geology, and climate) at the 41 streamgages and 167 low-flow partial-record stations. The regression analyses determined drainage area, soil permeability, average April precipitation, average June precipitation, and percent storage (water bodies and wetlands) were the significant explanatory variables for estimating the selected flow-duration and low-flow frequency statistics.

Streamflow estimates were computed for two land- and water-use conditions in New Jersey—land- and water-use during the baseline period of record (defined as the years a streamgage had little to no change in development and water use) and current land- and water-use conditions (1989–2008)—for each selected station using data collected through water year 2008. The baseline period of record is representative of a period when the basin was unaffected by change in development. The current period is representative of the increased development of the last 20 years (1989–2008). The two different land- and water-use conditions were used as surrogates for development to determine whether there have been changes in low-flow statistics as a result of changes in development over time. The State was divided into two low-flow regression regions, the Coastal Plain and the non-coastal region, in order to improve the accuracy of the regression equations. The left-censored parametric survival regression method was used for the analyses to account for streamgages and partial-record stations that had zero flow values for some of the statistics. The average standard error of estimate for the 348 regression equations ranged from 16 to 340 percent. These regression equations and basin characteristics are presented in the U.S. Geological Survey (USGS) StreamStats Web-based geographic information system application. This tool allows users to click on an ungaged site on a stream in New Jersey and get the estimated flow-duration and low-flow frequency statistics. Additionally, the user can click on a streamgage or partial-record station and get the “at-site” streamflow statistics.

The low-flow characteristics of a stream ultimately affect the use of the stream by humans. Specific information on the low-flow characteristics of streams is essential to water managers who deal with problems related to municipal and industrial water supply, fish and wildlife conservation, and dilution of wastewater.

First posted June 29, 2014

For additional information, contact:
Director, New Jersey Water Science Center
U.S. Geological Survey
3450 Princeton Pike, Suite 110
Lawrenceville, NJ 08648
http://nj.usgs.gov/

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Suggested citation:

Watson, K.M., and McHugh, A.R., 2014, Regional regression equations for the estimation of selected monthly low-flow duration and frequency statistics at ungaged sites on streams in New Jersey: U.S. Geological Survey Scientific Investigations Report 2014–5004, 59 p., http://dx.doi.org/10.3133/sir20145004.

ISSN 2328-0328 (online)



Contents

Abstract

Introduction

Methods for Dataset Development

Regional Regression Analyses to Estimate Selected Low-Flow Duration and Frequency Statistics for Ungaged Streams

Summary and Conclusions

References Cited

Appendix 1. Flow-duration and low-flow frequency values computed from observed continuous-record streamflow-gaging station and partial-record gaging station data, estimates predicted using regression equations, and percent difference between the two values for the non-coastal region in New Jersey for the baseline land- and water-use conditions.

Appendix 2. Flow-duration and low-flow frequency values computed from observed continuous-record streamflow-gaging station and partial-record gaging station data, estimates predicted using regression equations, and percent difference between the two values for the Coastal Plain region in New Jersey for the baseline land- and water-use conditions.

Appendix 3. Flow-duration and low-flow frequency values computed from observed continuous-record streamflow-gaging station and partial-record gaging station data, estimates predicted using regression equations, and percent difference between the two values for the non-coastal region in New Jersey for the current land- and water-use conditions, water years 1989–2008.

Appendix 4. Flow-duration and low-flow frequency values computed from observed continuous-record streamflow-gaging station and partial-record gaging station data, estimates predicted using regression equations, and percent difference between the two values for the Coastal Plain region in New Jersey for the current land- and water-use conditions, water years 1989–2008.

Appendix 5. Comparison of flow-duration and low-flow frequency values for continuous-record streamflow-gaging stations and partial-record stations in the non-coastal region in New Jersey between the baseline and current (water years 1989–2008) land- and water-use conditions.

Appendix 6. Comparison of flow-duration and low-flow frequency values for continuous-record streamflow-gaging stations and partial-record stations in the Coastal Plain region in New Jersey between the baseline and current (water years 1989–2008) land- and water-use conditions.


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