2026 Current Conditions

Weekly Water Quality Update 10/15/2026

Lake Winnisquam Approaches Fall Turnover

Lake Winnisquam continues its transition toward fall turnover, with surface water temperatures cooling and the thermocline pushing deeper into the water column.

Fall turnover has not occurred yet, but the lake is getting close. Our continuous monitoring buoys currently indicate a temperature difference of just 5°C between surface and bottom waters. With cooler temperatures and high winds expected, we anticipate that turnover could occur soon. These observations are consistent with the timing of fall turnover measured last year.

Water clarity declined slightly this week, likely influenced by recent rainfall and the ongoing lake drawdown. We will continue tracking water quality as the lake moves through this seasonal transition.

What Is Fall Turnover?

During summer, Lake Winnisquam develops distinct temperature layers. Warm water remains near the surface, while colder, denser water stays deeper in the lake. This separation, known as thermal stratification, limits mixing between the upper and lower water layers.

As autumn brings cooler temperatures and increased wind-driven mixing, the surface water cools and the temperature difference between surface and bottom waters decreases. Eventually, the lake mixes more completely from top to bottom in a process called fall turnover.

Turnover is an important seasonal transition because it redistributes heat, dissolved oxygen, and nutrients throughout the water column.

Continuous Monitoring Help Pinpoint Turnover

Our continuous monitoring buoys are giving WWN a new level of insight into this seasonal transition. Historically, our regular water quality sampling provided valuable snapshots of lake conditions, but it was difficult to determine precisely when turnover occurred between sampling events.

The buoys continuously measure water temperature at different depths, allowing us to follow the progression toward turnover and identify when the lake begins mixing.

Currently, the temperature difference between surface and bottom waters is approximately 5°C. This narrowing temperature gap suggests that the lake is approaching turnover, although the lake has not yet fully mixed.

With cooler temperatures and high winds expected, we will be watching the buoy data closely over the coming days.

These continuous measurements will also help WWN build a more detailed understanding of Lake Winnisquam's seasonal temperature patterns and how they change from year to year. We are excited to continue collecting this valuable data and look forward to understanding how conditions change through November. Learn more about our buoys here.

Fall Drawdown Begins October 12

The scheduled fall drawdown is set to begin October 12 and continue for approximately two weeks.

WWN is particularly interested in tracking lake conditions throughout this period. Continuous buoy measurements will allow us to observe changes in water temperature, dissolved oxygen, chlorophyll-a, and phycocyanin as the lake moves through fall turnover and the drawdown.

These data will help us better understand seasonal changes in Lake Winnisquam and how conditions in the water column evolve during this transition.

Monitoring Continues Through November

Our regular weekly water quality monitoring will soon conclude for the season. However, our continuous monitoring buoys will remain active into November, providing valuable information as Lake Winnisquam transitions through fall turnover and into late autumn.

WWN will continue sharing weekly updates highlighting what the buoy data reveal about changing water temperatures, dissolved oxygen, and indicators of algal and cyanobacteria activity.

As we expand our understanding of Lake Winnisquam through this new technology, each season of data will help us better understand the lake's natural patterns and identify changes that may warrant closer attention.

Get Involved

If you are interested in becoming involved with water quality monitoring or other volunteer stewardship opportunities, we encourage you to contact WWN. Community volunteers play a vital role in helping preserve and protect Lake Winnisquam and its watershed for future generations.

While these weekly updates often focus on scientific observations, they also remind us why protecting Lake Winnisquam matters. A healthy lake provides countless benefits to our community, from swimming, boating, paddling, and fishing to supporting wildlife, providing clean water, and offering a place to relax, reconnect, and create lasting memories with family and friends.

The continued health of Lake Winnisquam is the result of many people working together. Every lake-friendly action, whether it's cleaning, draining, and drying your boat, reducing runoff from your property, minimizing wake near shorelines, or respecting wildlife, helps preserve this incredible resource for future generations.

Fall is beginning to show itself around Lake Winnisquam. Enjoy the beautiful colors and the changing season!

Helpful links for current conditions:
For real-time lake level information, visit NHDES' Real-Time Data and Information page
For current advisories, watches, and warnings visit NHDES' Healthy Swimming Mapper.

Stay informed, stay safe, and check your inbox for your weekly water quality updates. Follow us on social media to stay updated on what’s happening around the lake.