Finger Lakes history · waterway
How Canadice Lake's Water Record Was Built—and Corrected
Two USGS reports, separated by seven decades, reveal how Canadice Lake was measured, where the record was limited, and how an error was formally corrected.
In February 1903, Rochester's city engineers established a gaging station at the outlet of Canadice Lake. A federal water-supply report published in 1911 described the apparatus: a standard thin-edged weir, additional rectangular gates, and an outflow controlled above the weir.
The method depended on repeated observation. The report said the depth on the weir was read each morning and whenever the gates changed. Larger discharges received a velocity correction, and the discharge was calculated with the Francis formula.
The same page also preserved an important provenance warning. The record had been furnished by Rochester city engineer E. A. Fisher and principal assistant city engineer John F. Skinner. USGS said its own engineers had not verified it.
Seven decades later, the 1982 New York water-data report described the lake and outlet together. It said Canadice outflow was diverted to Hemlock Lake for Rochester's water supply, regulated by gates, and augmented by pumping. It also said intermittent spillway flow was not monitored, reducing the accuracy of the adjusted record as an indication of natural runoff.
The 1982 report marked September of that year as the end of both the lake record at station 04228950 and the outlet record at station 04229000.
It also corrected a unit error in the reports for 1971 through 1981. Figures for changes in lake contents had been expressed in millions of cubic feet, but the earlier reports had mistakenly labeled them as millions of cubic feet per second.
Together, the reports show that a historical data series is not just a column of numbers. It has instruments, operators, formulas, unmeasured flow, institutional provenance, a period of record, and corrections that later readers need in order to use it responsibly.
Source note
The station's February 1903 establishment, weir and gates, observation method, formula, and unverified Rochester provenance appear on printed page 82 of USGS Water-Supply Paper 264, Surface Water Supply of the United States, 1909, Part IV, St. Lawrence River Basin (1911). The station numbers, September 1982 discontinuation, diversion and regulation notes, spillway limitation, and unit correction appear on printed page 91 of Water Resources Data, New York, Water Year 1982, Volume 3 (USGS, 1983). This story paraphrases and cites the reports; it reproduces no scan, table, typography, or other source media.