Lat 42°21'21", long
74°26'42" referenced to North American Datum of 1927,
Schoharie County, NY, Hydrologic Unit 02020005, in Shandaken
Tunnel intake house on Intake Road, 1.6 mi north of junction of
Intake Road and State Highway 23, 2.5 mi upstream from Gilboa
Dam, and 2.6 mi east of Grand Gorge.
PERIOD OF RECORD.--
January 1973 to current year. Monthly
contents only published as "at Gilboa" for September
1928 to December 1972.
WDR NY-86-1: 1956 (maximum
elevation). WDR NY-90-1: Drainage area.
Water-stage recorder. Supplementary nonrecording
gage used for periods when reservoir elevation is below
1,065.00 ft. Prior to November 2001, supplementary nonrecording
gage used for periods when reservoir elevation was below
1,072.50 ft. Datum of gage is NGVD of 1929 (levels by Board of
Water Supply, City of New York). To convert elevations to NAVD
of 1988, subtract 0.60 ft (VERTCON).
Capacity table and once-daily nonrecording
gage readings provided by Department of Environmental
Protection, City of New York.
Reservoir is formed by masonry and earth dam.
Storage began July 24, 1926. Usable capacity 19,583 mil gal
between minimum operating level, elevation 1,050.00 ft, and
crest of spillway, elevation 1,130.00 ft. Dead storage below
elevation 1,050.00 ft, 1,968 mil gal. Figures given herein
represent usable contents. A 220 ft-wide notch was cut into the
1,324 ft-wide spillway in February 2006, elevation of the crest
of the notch 1,124.5 ft, and four 4 ft-diameter siphons were
installed on the dam in March 2006. The construction of the
notch and siphons are part of a dam and spillway reconstruction
and modification project. Additional information on
modifications that have taken place since 2006 and a project
description and schedule can be accessed at
Reservoir impounds water except for periods of spilling, for
diversion through Shandaken Tunnel into Esopus Creek to Ashokan
Reservoir, for New York City water supply.
Capacity table (elevation, in feet, and usable contents, in million gallons)
Elevation Contents Elevation Contents
1,050.0 0 1,120.0 16,097
1,060.0 1,216 1,130.0 19,583
1,080.0 4,969 1,133.0 20,700
1,100.0 10,080 1,140.0 23,637
EXTREMES FOR PERIOD OF RECORD.--
1,137.73 ft, Aug. 28, 2011, contents, 22,679 mil gal; minimum
elevation observed (after initial filling), 1,062.00 ft, Aug.
20, 1970, contents, 1,520 mil gal.