HADLEY — Reservoir waters have been rising steadily higher and higher at the Conklingville Dam.
Levels are less than a foot and a half from brimming the spillway, a slide-like structure designed to provide prescribed discharges of excess water from the Great Sacandaga Lake to the Sacandaga River.
“We may see water just conveyed just over the spillway or it could just crest short of that,” said John Callaghan, executive director of Hudson River-Black River Regulating District.
Water levels, as of Tuesday, are at 769.74 feet (NAVD 1988 datum) at the Hadley site, whereas at the same time last year, that figure hovered around 769.50 feet, according to the United States Geological Survey. It’s expected to jump as high as 770.2 feet on Friday and Saturday before lowering.
The last time water went over the spillway crest was in 2019 at levels of 772.71 feet. Beyond that, it’s typically strayed from 770.1 (NAVD 1988) or 771-foot (NGVD 1929 datum) spill line in recent years, USGS data shows.
So-called moderate flooding is defined by levels exceeding 773.5 feet, and severe flooding, 774 feet. The largest overflow in history was recorded at 774.47 feet in spring of 2011 — something of an anomaly in the dam’s 94-year history.
“Of course, we don’t consider this to be scary levels or anything near it, but 2011, over a decade ago, was when it was well above the spillway crest,” Callaghan said.
While kicking out a bevy of residents and flooding entire communities in the process long ago, the reservoir was created by the public-benefit corporation as a means of preventing devastating yearly floods along the Hudson River.
Each spring the 29-mile long reservoir fills up as a result of snowmelt and rainfall in order to mitigate downstream freshets (the Hudson River connects to the Sacandaga River around Lake Luzerne). Like natural bodies of water, sudden meteorological shifts can cause the inflow to exceed the outflow at varying points between March and late May.
The early May timing of 769-foot-plus dam levels could be the result of late winter snowfall, according to Britt Westergard, a hydrologist with the National Weather Service in Albany. A March 14 nor’easter pummeled much of northeastern New York.
“We were really very lucky this spring with that much snow that fell in March, we could’ve been looking at really significant flooding if we had just the right combination of rainfall and snowmelt happening at the same time,” said Westergard. “We really dodged a bullet there.”
Tyler A. McNeil can be reached at 518-395-3047 or [email protected] Follow him on Facebook at Tyler A. McNeil, Daily Gazette or Twitter @TylerAMcNeil.