Independent New Hampshire Journalism · Northfield, NH

Lake Winnipesaukee’s Two Lowest Years in a 67-Year Federal Gauge Record Were 1941 and 1965. They Were Also New Hampshire’s Two Driest Years on Record.

The U.S. Geological Survey read the lake’s level at Weirs Beach every day from November 1937 through June 2005. The record shows a lake that climbs with the spring melt, crests in May and sinks again by late winter, and it shows how closely the low years followed the dry ones.

From Nov. 24, 1937, through June 30, 2005, the U.S. Geological Survey published a reading of Lake Winnipesaukee’s water level for every single day, 24,691 of them, from a gauge at Weirs Beach, in Belknap County. That record covers 67 full calendar years, 1938 through 2004. The two years with the lowest average level in it were 1941 and 1965. In the statewide precipitation record kept by the National Oceanic and Atmospheric Administration, which runs from 1895 through 2025, those were New Hampshire’s two driest years.

The gauge reports the lake’s height in feet above a fixed reference point that the survey sets at 500.00 feet above the National Geodetic Vertical Datum of 1929, a national elevation baseline. A reading of 4.00 feet means the water stood 504 feet above that baseline. Across all 67 years, the daily readings averaged 3.34 feet.

A managed lake

Lake Winnipesaukee is not left to rise and fall on its own. The survey’s station notes say its “Stage regulated at outlet and by Wentworth, Merrymeeting, and other lakes.” The outlet is at Lakeport, and the lake drains 363 square miles. The same notes describe the lake as “used for recreation and conservation for development of water power.”

The survey lists the lake’s usable storage as 7.21 billion cubic feet of water between elevations of 500.57 and 504.24 feet, which on the gauge are readings of 0.57 and 4.24. A capacity table the survey credits to the state Department of Environmental Services shows how much water one foot holds: between gauge readings of 2 and 5 feet, each foot of height adds between 1.97 billion and 2.01 billion cubic feet. At 7.48 gallons to the cubic foot, that is roughly 15 billion gallons for every foot the lake rises or falls.

The yearly cycle

Averaged over 1938 through 2004, the lake ran lowest in February, at 2.66 feet, and highest in May, at 4.29 feet, a seasonal swing of about 1.6 feet. The level climbed fastest from March to April, held near its peak through June, and drifted down through summer and fall.