Five-foot drawdown: When will the lake be lowered?

August 18, 2023| Community

By: Holly Odgers

Every five years, the New Jersey Department of Environmental Protection (NJDEP) lowers the water level on Lake Hopatcong by 60 inches (5 feet), to allow for inspection and repairs to shoreline structures including the dam at Hopatcong State Park. Residents can contact their municipal town hall and Hopatcong State Park (973-398-7010) to inquire about needed permits for work on waterfront structures.

The drawdown also allows for cleanup of the lakebed and may reduce aquatic weeds for the following season. A Lake-Wide Cleanup, scheduled for November 4, is being organized to take advantage of the ability to remove debris from the exposed lakebed.

The timing of the drawdown is intended to allow for repairs before winter weather sets in, with refill beginning early enough to reduce the likelihood of impact on the lake’s water level the following boating season.

According to NJDEP’s 2011 Lake Hopatcong Water Level Management Plan, the target date for the lake to fully drop 60 inches (5 feet) is November 1, with a drawdown rate of 1.5 inches per day. If the lake level is at 9 feet, the drawdown will begin on September 22. That date of initiation will be adjusted based on the water level reading at the Hopatcong State Park dam, with the start date adjusted one day earlier or later for each 1.5-inch deviation from the 9-foot mark. The rate of drawdown shall be adjusted to account for rainfall throughout the drawdown period in order to reach a water elevation in the lake of 4 feet (60 inches, or 5 feet, below the crest of the dam at 9 feet) by November 1.

The lake will remain at the 60-inch (5-foot) drawdown level from November 1 to December 15. After that, the refill will begin and continue until the annual 22" drawdown level is reached (as indicated in the 2016 Lake Hopatcong Water Level Management Pilot Program) or until ice forms. It will remain at this level until it is determined that the spring thaw has softened the ice on the lake sufficiently enough to avoid ice damage to private property, at which point, the lake shall be allowed to fill to the crest of the dam at 9 feet.

You can view the current lake level HERE.

Source: 2011 Lake Hopatcong Water Level Management Plan