Fallin’ lake levels: Drawdown helps lake ecosystems to thrive

Fall is here, marked by the cool morning air and colorful leaves that mark the season. A week away from Columbus Day weekend, both locals and visitors are enjoying everything autumn has to offer, counting down the days to the Sandwich Fair, going apple picking and taking in the foliage. It’s the perfect time to experience the unique fall activities in the Lakes Region.

While everyone is out appreciating the changing of the seasons, Lake Winnipesaukee along with many other lakes throughout New Hampshire will begin experiencing a change, as well. In early September, the New Hampshire Department of Environmental Services announced the dates of the state's fall drawdown of the lakes, most of which occur toward the end of Columbus Day weekend.

Why do we draw down our lakes? Lake drawdowns are performed annually during the fall as an effort to reduce winter ice damage to shoreline properties and to reduce spring flooding. Lowering the lake levels also provides opportunities for towns and homeowners to perform maintenance or address any repairs to waterfront structures or properties. There are some other benefits to lake drawdowns, such as aquatic plant control. Drawdowns may stress plants; the low water levels can result in plants drying out, subsequently affecting their ability to grow. Additionally, plants may also be physically removed from their habitat as a result of ice scouring, dependent upon ice-in. Together, these effects may temporarily reduce plant density along the shore for a period of time.

The length of drawdown of a lake or pond depends on snow and ice cover, water uses and expected water renewal rates. Drawdown is also not an overnight event, it happens gradually. The lake levels are brought down slowly in order for aquatic fauna, such as mollusks and amphibians, to adapt to the changing water level. October into November is the typical time for lake drawdowns; the degree and date of the start of drawdown for each lake varies since the hydrologic conditions and recreational uses of each waterbody varies. Additionally, the amount of rainfall during that period and operational constraints can cause the drawdown start date to vary.

Many lakes across the state will begin to be drawn down toward the end of next weekend, including Opechee, Squam, and Winnisquam.

According to NH Department of Environmental Services “…the drawdowns of Opechee and Winnisquam Lakes, which occur on a two-year interval, last only approximately two weeks. This year, the lowering of Opechee Lake will begin on Oct. 14, and it will likely take two days to pass the water from Opechee Lake downstream through Winnisquam Lake. Therefore, the level of Winnisquam Lake is not expected to drop noticeably until Oct. 16. On Oct. 28 flows at Lakeport Dam will be increased to refill Opechee Lake, and the level of Winnisquam Lake should begin to rise late in the day on Oct. 29.”

Lake Winnipesaukee is a special case when it comes to the annual statewide fall drawdown. Winnipesaukee is not purposely drawn down but instead, releases from the Lakeport Dam are reduced. The average output of the Lakeport Dam is 250 cubic feet per second  but after Oct. 9, this will be reduced to a flow between 30 and 50 cfs for a period of up to two weeks. This rate of flow is chosen because 30 to 50 cfs is the minimum flow needed to maintain aquatic life downstream. The reduction will allow for maintenance to be conducted on the dams and hydropower facilities on the Winnipesaukee River.

By the middle of the fall, Lake Winnipesaukee is approximately 15 inches below its springtime full level on average. As a result of the reduction in the amount of water released from the Lakeport Dam, the lake level does not drop for the remainder of October and is maintained at this level through December. Maintaining a stable lake level is important for aquatic species that call Lake Winnipesaukee home, like the lake trout that spawn right around Halloween each year. It’s important that the lake level does not fall too low, to avoid stranding the eggs.

Just like the cycle of the seasons with leaves returning in the spring, lake levels will be brought back up before the summer season. It’s important that the lake levels are returned to normal before summer for many reasons, including recreational and aesthetic purposes.

It’s also important ecologically, for the aquatic species and for keeping terrestrial species from encroaching on the lake bed. If you’d like to learn more about fall drawdown and the drawdown depths that the New Hampshire lakes will experience, check out NHDES press release at www.des.nh.gov/news-and-media/state-announces-its-2024-fall-drawdown-lakes.

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Bree Rossiter is the conservation program manager for the Lake Winnipesaukee Alliance. She manages the water quality monitoring program, cyanobacteria monitoring initiatives, the Winni Blue/LakeSmart program, and assists with watershed management planning efforts. Bree can be reached at brossiter@winnipesaukee.org. The Lake Winnipesaukee Alliance is a nonprofit dedicated to protecting the water quality and natural resources of the lake and its watershed. To learn more, visit winnipesaukee.org.