Bathymetry of Ashokan, Cannonsville, Neversink, Pepacton, Rondout, and Schoharie Reservoirs, New York, 2013–15

Scientific Investigations Report 2017-5064
Prepared in cooperation with the New York City Department of Environmental Protection
By:

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Abstract

Drinking water for New York City is supplied from several large reservoirs, including a system of reservoirs west of the Hudson River. To provide updated reservoir capacity tables and bathymetry maps of the City’s six West of Hudson reservoirs, bathymetric surveys were conducted by the U.S. Geological Survey from 2013 to 2015. Depths were surveyed with a single-beam echo sounder and real-time kinematic global positioning system along planned transects at predetermined intervals for each reservoir. A separate quality assurance dataset of echo sounder points was collected along transects at oblique angles to the main transects for accuracy assessment. Field-survey data were combined with water surface elevations in a geographic information system to create three-dimensional surfaces in the form of triangulated irregular networks (TINs) representing the elevations of the reservoir geomorphology. The TINs were linearly enforced to better represent geomorphic features within the reservoirs. The linearly enforced TINs were then used to create raster surfaces and 2-foot-interval contour maps of the reservoirs. Elevationarea-capacity tables were calculated at 0.01-foot intervals. The results of the surveys show that the total capacity of the West of Hudson reservoirs decreased by 11.5 billion gallons (Ggal), or 2.3 percent, because of sedimentation since construction, and the useable capacity (the volume above the minimum operating level required to deliver full flow for drinking water supply) has decreased by 7.9 Ggal (1.7 percent). The available capacity (the volume between the spillway elevation and the lowest intake or sill elevation used for drinking water supply) decreased by 9.6 Ggal (2.0 percent), and dead storage (the volume below the lowest intake or sill elevation) decreased by 1.9 Ggal (11.6 percent). The elevation of the spillway at Schoharie Reservoir was changed because of reconstruction during 2015, resulting in an additional decrease of 0.1 Ggal in total, useable, and available capacity.

Suggested Citation

Nystrom, E.A., 2018, Bathymetry of Ashokan, Cannonsville, Neversink, Pepacton, Rondout, and Schoharie Reservoirs, New York, 2013–15 (ver. 1.2, November 2018): U.S. Geological Survey Scientific Investigations Report 2017–5064, 29 p., https://doi.org/10.3133/sir20175064.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Methods
  • Accuracy Assessment
  • Results of Surveys
  • Summary
  • References Cited

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Bathymetry of Ashokan, Cannonsville, Neversink, Pepacton, Rondout, and Schoharie Reservoirs, New York, 2013–15
Series title Scientific Investigations Report
Series number 2017-5064
DOI 10.3133/sir20175064
Edition Version 1.0: Originally posted February 1, 2018; Version 1.1: February 12, 2018, Version 1.2: November 21, 2018
Year Published 2018
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) New York Water Science Center
Description Report: ix, 29 p.; 6 Data Releases
Country United States
State New York
Other Geospatial Ashokan, Cannonsville, Neversink, Pepacton, Rondout, and Schoharie Reservoirs
Online Only (Y/N) Y
Additional Online Files (Y/N) N