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Bathymetric survey and estimation of storage capacity of lower Sixmile Creek reservoir, Ithaca, New York

Open-File Report 2016-1157

Prepared in cooperation with the City of Ithaca, New York, and the New York State Department of State
By:
, , and
https://doi.org/10.3133/ofr20161157

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Abstract

During 2015, the U.S. Geological Survey, in cooperation with the City of Ithaca, New York, and the New York State Department of State, conducted a bathymetric survey of the lower Sixmile Creek reservoir in Tompkins County, New York. A former water-supply reservoir for the City of Ithaca, the reservoir is no longer a functional component of Ithaca’s water-supply system, having been replaced by a larger reservoir less than a mile upstream in 1911. Excessive sedimentation has substantially reduced the reservoir’s water-storage capacity and made the discharge gate at the base of the 30-foot dam, which creates the reservoir, inoperable. U.S. Geological Survey personnel collected bathymetric data by using an acoustic Doppler current profiler. Across more than half of the approximately 14-acre reservoir, depths were manually measured because of interference from aquatic vegetation with the acoustic Doppler current profiler. City of Ithaca personnel created a bottom-elevation surface from these depth data. A second surface was created from depths that were manually measured by City of Ithaca personnel during 1938. Surface areas and storage capacities were computed at 1-foot increments of elevation for both bathymetric surveys. The results indicate that the current storage capacity of the reservoir at its normal water-surface elevation is about 84 acre-feet and that sediment accumulated between 1938 and 2015 has decreased the reservoir’s capacity by about 68 acre-feet. This sediment load is attributed to annual inputs from the watershed above the reservoir, as well as from an episodic landslide that filled a large part of the reservoir along its northern edge in 1949.

Suggested Citation

Wernly, J.F., Zajd, H.J., Jr., and Coon, W.F., 2016, Bathymetric survey and estimation of storage capacity of lower Sixmile Creek reservoir, Ithaca, New York: U.S. Geological Survey Open-File Report 2016–1157, 13 p., http://dx.doi.org/10.3133/ofr20161157.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Bathymetric Survey
  • Dam and Normal Pool Water-Surface Elevations
  • Creation of Bathymetric Surface
  • Estimation of Surface Area and Storage Capacity
  • Summary
  • References Cited

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Bathymetric survey and estimation of storage capacity of lower Sixmile Creek reservoir, Ithaca, New York
Series title:
Open-File Report
Series number:
2016-1157
DOI:
10.3133/ofr20161157
Year Published:
2016
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
New York Water Science Center
Description:
Report: vii, 13 p.; Data Release
Country:
United States
State:
New York
City:
Ithaca
Other Geospatial:
Lower Sixmile Creek Reservoir
Online Only (Y/N):
Y
Additional Online Files (Y/N):
Y