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Scientific Investigations Report 2014–5220

Prepared in cooperation with The Nature Conservancy and the New York State Energy Research and Development Authority

Estimation of Unaltered Daily Mean Streamflow at Ungaged Streams of New York, Excluding Long Island, Water Years 1961–2010

By Christopher L. Gazoorian

Thumbnail of and link to report PDF (5.63 MB)Abstract

The lakes, rivers, and streams of New York State provide an essential water resource for the State. The information provided by time series hydrologic data is essential to understanding ways to promote healthy instream ecology and to strengthen the scientific basis for sound water management decision making in New York. The U.S. Geological Survey, in cooperation with The Nature Conservancy and the New York State Energy Research and Development Authority, has developed the New York Streamflow Estimation Tool to estimate a daily mean hydrograph for the period from October 1, 1960, to September 30, 2010, at ungaged locations across the State. The New York Streamflow Estimation Tool produces a complete estimated daily mean time series from which daily flow statistics can be estimated. In addition, the New York Streamflow Estimation Tool provides a means for quantitative flow assessments at ungaged locations that can be used to address the objectives of the Clean Water Act—to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.

The New York Streamflow Estimation Tool uses data from the U.S. Geological Survey streamflow network for selected streamgages in New York (excluding Long Island) and surrounding States with shared hydrologic boundaries, and physical and climate basin characteristics to estimate the natural unaltered streamflow at ungaged stream locations. The unaltered streamflow is representative of flows that are minimally altered by regulation, diversion, or mining, and other anthropogenic activities. With the streamflow network data, flow-duration exceedance probability equations were developed to estimate unaltered streamflow exceedance probabilities at an ungaged location using a methodology that equates streamflow as a percentile from a flow-duration curve for a particular day at a hydrologically similar reference streamgage with streamflow as a percentile from the flow-duration curve for the same day at an ungaged location. The reference streamgage is selected using map correlation, a geostatistical method in which variogram models are developed that correlate streamflow at one streamgage with streamflows at all other locations in the study area. Regression equations used to predict 17 flow-duration exceedance probabilities were developed to estimate the flow-duration curves at ungaged locations for New York using geographic information system-derived basin characteristics.

A graphical user interface, with an integrated spreadsheet summary report, has been developed to estimate and display the daily mean streamflows and statistics and to evaluate different water management or water withdrawal scenarios with the estimated monthly data. This package of regression equations, U.S. Geological Survey streamgage data, and spreadsheet application produces an interactive tool to estimate an unaltered daily streamflow hydrograph and streamflow statistics at ungaged sites in New York. Among other uses, the New York Streamflow Estimation Tool can assist water managers with permitting water withdrawals, implementing habitat protection, estimating contaminant loads, or determining the potential affect from chemical spills.

First posted February 6, 2015

For additional information, contact:
Director, New York Water Science Center
U.S. Geological Survey
425 Jordan Road
Troy, NY 12180
(518) 285-5600

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Suggested citation:

Gazoorian, C.L., 2015, Estimation of unaltered daily mean streamflow at ungaged streams of New York, excluding Long Island, water years 1961–2010: U.S. Geological Survey Scientific Investigations Report 2014–5220, 29 p.,

ISSN 2328-0328 (online)




Estimation of Unaltered Daily Mean Streamflow

Using the New York Streamflow Estimation Tool for Estimating Unaltered Daily Mean Streamflow for Ungaged Locations

Accuracy and Limitations of Estimated Unaltered Streamflows


References Cited

Appendix 1. Flow-Duration Exceedance Probabilities, Observed and Computed From Streamflow Data, and Regression Equations for Streamgages Used in Regression Analysis

Appendix 2. Description of Reference Streamgages Used in the Development of the New York Streamflow Estimation Tool With Period of Record and Use of Data

Appendix 3. Reference Streamgages With Index Streamgage Used for MOVE.3 Record Extension

Appendix 4. Basin Characteristics Used in the Development of Flow-Duration Regression Equations

Appendix 5. User’s Guide for the New York Streamflow Estimation Tool (NYSET)

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