Water Quality
Overall Assessment
Overall, the August 7 results remain encouraging for this point in the summer. Water clarity improved slightly to 3.05 m (10 ft 0 in) and remains substantially better than at the same time in 2024 and 2025.
Water temperatures have fluctuated in response to changing summer weather conditions, including periods of strong wind, warmer days, and cooler nights. Recent readings show this variability rather than a consistent warming or cooling trend, with the most recent surface temperature increasing again. Wind-driven mixing appears to have influenced portions of the upper and middle water column and help explain the improved dissolved oxygen observed at intermediate depths.
Below approximately 9 m (29 ft 6 in), dissolved oxygen remains critically low at 0.4–0.5 mg/L. This deep-water oxygen depletion remains the primary water-quality concern and creates conditions favorable for phosphorus release from bottom sediments.
The overall picture is therefore mixed but favorable compared with recent summers: unusually good August water clarity and improved mid-depth oxygen, but persistent severe oxygen depletion in the deepest water. Continued monitoring will show whether these favorable clarity and mid-depth oxygen conditions persist through the remainder of the summer.
August 7, 2026 Water Quality Report
Secchi Disc Transparency
Water Clarity (Secchi Disk)
Water clarity has remained relatively strong throughout the 2026 season, improving through June and reaching 3.76 m (12 ft 4 in) on July 10. After declining to 2.90 m (9 ft 6 in) on July 24, clarity improved slightly to 3.05 m (10 ft 0 in) on August 7.
Most encouraging is how well clarity has been maintained into August. At approximately the same point, Secchi depth had declined to 1.93 m (6 ft 4 in) in 2024 and 1.39 m (4 ft 7 in) in 2025. The August 7 reading remains substantially better than either of the previous two years.
Temperature - YTD
Water Temperature - YTD overview
Water temperatures show the expected overall seasonal warming from spring into summer, rising from 13.0°C (55.4°F) on May 15 to 26.5°C (79.7°F) on August 7. Surface temperatures have fluctuated considerably along the way, reflecting changing weather conditions, including periods of strong winds, warm weather, and cooler nights.
Dissolved Oxygen - YTD
Dissolved Oxygen - YTD Trend
Dissolved oxygen shows a clear seasonal decline in the deeper portions of the lake as summer stratification developed. In mid-May, oxygen was well distributed throughout the water column at approximately 9.4–9.8 mg/L. By late June, significant oxygen depletion had developed below approximately 7 m (23 ft), and by July extremely low oxygen concentrations were present in the deepest water.
The August 7 profile shows some improvement at middle depths, likely influenced by recent strong winds. At 8 m (26 ft 3 in), dissolved oxygen increased from 2.1 mg/L on July 24 to 4.5 mg/L on August 7, while at 7 m (23 ft) it increased from 5.2 to 6.1 mg/L.
However, this mixing has not reached the deepest water. At 9–11 m (29 ft 6 in–36 ft 1 in), dissolved oxygen is now only 0.4–0.5 mg/L. The seasonal trend therefore continues to show severe deep-water oxygen depletion despite improved conditions higher in the water column.
July 24, 2026 Water Quality Report
Overall Assessment
Although Unity Pond continues to appear healthy, several indicators suggest the lake is entering the period when conditions become more favorable for cyanobacterial growth.
Water clarity remains good at 2.90 meters (9.5 feet)—well above the traditional 2-meter bloom threshold and substantially better than at this time in both 2024 and 2025. However, water clarity is only one indicator of lake conditions.
The lake remains strongly stratified, with very low dissolved oxygen in the deepest waters. In addition, the Subtidal buoy has recorded an increase in phycocyanin—the pigment unique to cyanobacteria—over the past two weeks. No surface bloom has been observed, but the trend suggests cyanobacteria are becoming more active as the lake progresses through late July.
To better understand what these readings mean, we collected water samples this week for laboratory analysis of microcystins, a toxin that can be produced by some species of cyanobacteria. The results will be compared with the Subtidal buoy's phycocyanin measurements to help evaluate how well the buoy's early-warning readings correspond with actual toxin levels. We expect the laboratory results in approximately 10 days.
None of these observations, by themselves, indicate that a harmful bloom is occurring. Taken together, however, they reinforce the importance of continued monitoring during the weeks ahead. Historically, late July through August has been the period when bloom conditions have been most likely to develop in Unity Pond.
Secchi Disc Transparency
Water Clarity (Secchi Disk)
The Secchi disk reading on July 24 was 2.90 meters (9.5 feet), a decrease from 3.76 meters (12.3 feet) on July 10. While this represents a noticeable reduction in clarity over the past two weeks, the lake remains well above the traditional 2-meter (6.6-foot) threshold commonly used to indicate bloom conditions.
Compared with previous years, water clarity remains encouraging. The July 24 reading is substantially clearer than the 1.88-meter reading recorded at approximately the same time in 2025, and also better than the 2.05-meter reading from 2024.
The decrease is typical for late July as the lake warms and biological activity increases, but overall clarity continues to compare favorably with the past two summers.
Temperature and Dissolved Oxygen
Temperature Profile
Surface water temperature measured 23.6°C (74.5°F), about 0.9°C cooler than the same period in 2025.
The temperature profile shows the lake remains strongly stratified. The upper 6–7 meters (20–23 feet) are warm and well mixed, while temperatures decline rapidly below that depth, reaching approximately 16.0°C (60.8°F) near the bottom.
Compared with 2025:
Surface waters were modestly cooler.
Water below approximately 6 meters was 1.3–1.7°C warmer than last year.
The average temperature throughout the water column was essentially unchanged from 2025.
Dissolved Oxygen Profile
Surface dissolved oxygen measured 7.5 mg/L, down from 8.2 mg/L on July 10, reflecting the expected seasonal decline as warmer water holds less oxygen.
One notable change this sampling period was the improvement in dissolved oxygen between 5 and 8 meters (16–26 feet) compared with two weeks earlier.
At 5 meters, dissolved oxygen increased from 4.8 to 7.2 mg/L.
At 6 meters, it increased from 3.6 to 7.2 mg/L.
At 7 meters, it rose from 1.9 to 5.2 mg/L.
At 8 meters, it increased from 1.2 to 2.1 mg/L.
This improvement may reflect the effect of strong winds the last few days, temporarily introducing oxygen into the middle portion of the lake.
Despite this improvement, dissolved oxygen concentrations below approximately 9 meters (30 feet) remain extremely low, ranging from 0.5 to 0.7 mg/L, indicating that the deepest waters continue to be essentially oxygen depleted. These low-oxygen conditions increase the likelihood that phosphorus will be released from the lake sediments into the overlying water. This process, known as internal phosphorus loading, can provide additional nutrients that may help fuel algae and cyanobacterial growth later in the summer.
Maine DEP Webite - Algal Blooms in Maine Lakes
July 10, 2026 Water Quality Report
Overall Summary
The July 10 results show both encouraging and cautionary signs.
The encouraging news is that water clarity remains strong for this time of year. The July 10 Secchi reading was 3.76 meters, (12.3 feet), and is better than what we typically see this time of year.
The concern is that the lake is warmer than last year and remains strongly stratified. Dissolved oxygen is still good in the upper 4 meters, (13 feet), but drops sharply below about 5 meters, (16 feet). Near the bottom, oxygen levels are very low.
Low oxygen in the deeper water can contribute to phosphorus release from lake sediments. That phosphorus can help fuel algae and cyanobacteria growth as the lake continues to warm and Dissolved Oxygen continues to decrease.
The Subtidal buoy is still in its calibration period. However, the buoy is showing an increasing phycocyanin level, which can indicate increasing cyanobacteria activity. This does not by itself confirm the start of a bloom, but it is a trend we will continue to monitor alongside Secchi readings, visual observations, and manual water-quality measurements.
For now, the lake appears visually clear at the monitoring station, but conditions are entering the part of the season when changes can happen quickly. Continued monitoring through both manual readings and the Subtidal buoy remains important.
Secchi Disc Transparency
Secchi Disk Transparency - July 10, 2026
The Secchi disk reading on July 10 was 3.76 meters (12.3 feet). That is a noteworthy improvement from the June 26 reading of 3.28 meters (10.8 feet) and is better than we typically see this time of year.
At this point, the lake is not showing the reduced clarity typically associated with the start of an active bloom. However, past years show that clarity can decline quickly later in July and early August, so this remains an important period to monitor closely.
Temperature and Dissolved Oxygen
Temperature Profile — July 10, 2026
Surface water temperature measured 26.2°C, (79.2°F). This was approximately 1.8°C, (3.2°F), warmer than the comparable July 11, 2025 reading.
The full water column was also warmer than last year, averaging 19.87°C, (67.8°F), compared with 18.44°C, (65.2°F), in 2025.
The lake remains strongly stratified. The upper water column is very warm, while temperatures begin to drop more noticeably below approximately 4 meters, (13 feet). This stratification limits mixing and reduces the ability of oxygen-rich surface water to replenish deeper areas.
Dissolved Oxygen Profile — July 10, 2026
Surface dissolved oxygen remains healthy at 8.2 mg/L, with good oxygen levels continuing through the upper 4 meters, (13 feet).
However, oxygen concentrations decline rapidly below approximately 5 meters, (16 feet). Readings fell to just 0.6 mg/L at 11 meters (36 feet).
Compared with the similar July 2025 reading, average dissolved oxygen was slightly higher in 2026, averaging 4.15 mg/L compared with 3.83 mg/L in 2025. However, the distribution remains concerning because the deeper water is already severely oxygen depleted.
Very low oxygen near the bottom can contribute to phosphorus release from lake sediments. Under low-oxygen conditions, phosphorus that is naturally bound to iron in the bottom sediments can be released back into the water column. Once available in the water, that phosphorus can act as a fertilizer for algae and cyanobacteria growth as summer conditions continue.
This is one of the major reasons alum treatments are beneficial. Alum chemically binds with phosphorus, including phosphorus that would otherwise be released from the sediments under low-oxygen conditions from the bottom sediment. Once bound to alum, the phosphorus is far less available to fuel algae and cyanobacteria growth in the water column.
Informal Lake Observation – June 28, 2026
The water appeared noticeably clearer along the shoreline today. Because of this, I took an informal Secchi disk reading, which measured 3.60 meters (11.8 feet), compared to the official monitoring result of 3.14 meters (10.3 feet) collected on June 26 under heavily overcast conditions.
Why might the water appear clearer?
The improved water clarity may reflect a combination of factors, including:
Better viewing conditions. Bright skies and calm water can make the Secchi disk visible at greater depths.
Calmer weather. Fine suspended particles naturally settle during periods of calm weather, improving water clarity.
Natural biological processes. Zooplankton feed on microscopic algae, which can temporarily increase water clarity.
Normal day-to-day lake changes. Natural fluctuations in algae distribution and other lake conditions can also influence water transparency.
Because Secchi disk measurements are influenced by weather, sunlight, and surface conditions, this observation should not be interpreted as a significant change in overall lake health. Our official water quality assessments are based on standardized biweekly monitoring conducted under consistent procedures.
We will continue to monitor water clarity throughout the season .
About Informal Lake Observations
Between scheduled monitoring events, Friends of Lake Winnecook may occasionally share field observations of changing lake conditions. These observations provide additional context and help document day-to-day conditions but are not part of our standardized long-term monitoring dataset.
June 26, 2026 Water Quality Report
Overall Summary
Water clarity improved from the previous sampling event but remains below the level observed at this point in both 2024 and 2025.
Recent cooler weather slowed warming of the lake surface, resulting in surface temperatures approximately 3°C (5–6°F) cooler than one year ago.
The lake remains strongly stratified, with little mixing between the warm surface waters and the cooler bottom waters.
Dissolved oxygen in the deeper portions of the lake continues to decline earlier than expected, a trend that could contribute to increased phosphorus release and elevate the risk of nuisance algae and cyanobacteria blooms later this summer.
Secchi Disc Transparency
Secchi Disk Transparency - June 26, 2026
The Secchi Disc reading on June 26 measured 3.28 meters (10.8 feet), an improvement from 3.14 meters recorded on June 12. While this represents a positive short-term change, clarity remains below the 3.40-meter reading observed at this point in 2025 and well below the 3.93-meter reading recorded in 2024.
Although water clarity remains good, the long-term seasonal trend continues to suggest the lake is progressing toward reduced clarity earlier than in previous years.
Temperature and Dissolved Oxygen
Temperature Profile 6/26/2026
Surface water temperature measured 21.1°C (70.0°F), approximately 3°C (5–6°F) cooler than on June 27, 2025. The recent stretch of cooler weather has slowed warming of the upper water column.
Despite the cooler surface temperatures, the lake remains strongly stratified. The thermocline is well established between approximately 6 and 8 meters (20–26 feet), limiting oxygen replenishment to deeper waters.
Dissolved Oxygen Profile 6/26/2026
Surface dissolved oxygen remains healthy at 8.4 mg/L. However, oxygen concentrations decline rapidly below approximately 7 meters (23 feet), with readings falling to 4.3 mg/L at 7 meters, 3.5 mg/L at 8 meters, and just 1.2 mg/L at 11 meters.
Compared with the same time last year, oxygen depletion in the deeper portions of the lake is occurring earlier. While average dissolved oxygen throughout the water column was only modestly lower than in 2025, the distribution of oxygen is more concerning because the lower water column is losing oxygen sooner in the season.
June 12th 2026 Water Quality Report
Overall Summary
Overall Lake Condition Assessment
Unity Pond entered mid-June 2026 with generally favorable water quality conditions.
The lake has warmed substantially faster than during the same period in 2025, resulting in stronger thermal stratification and a well-developed thermocline. Although the June 12, 2026 sampling date was three days earlier than the June 15, 2025 comparison date, surface waters were already about 4°C (7°F) warmer. In addition, the lake is approximately 1.5 feet lower than at this time last year. The combination of lower water levels, warm weather, and increased solar heating likely contributed to the earlier warming and stronger stratification observed in 2026.
Despite the accelerated warming, dissolved oxygen concentrations remain stronger than those observed at the same time in 2025, and adequate oxygen is present throughout the measured water column. Water clarity has also improved since late May and has returned to essentially the same level observed in mid-June 2025.
Biological Considerations
The improvement in water clarity since late May may reflect normal seasonal changes in the lake's plankton community. During spring and early summer, populations of microscopic algae (phytoplankton) increase as water temperatures rise and nutrients become available. At the same time, populations of tiny grazing animals (zooplankton) expand and feed on those algae.
As zooplankton populations grow, they can reduce the amount of suspended algae in the water, improving clarity. The increase in Secchi depth from 2.88 meters (9.4 feet) on May 29 to 3.14 meters (10.3 feet) on June 12 is consistent with this seasonal pattern.
Overall, current conditions suggest the lake remains biologically productive without signs of excessive algal growth. Water clarity is good for mid-June, dissolved oxygen remains strong throughout the water column, and there is no indication from the Secchi data of a significant algal bloom.
Potential Concerns
Earlier and stronger stratification is not inherently negative, but it can have consequences later in the summer.
Once stratification becomes established, oxygen from the atmosphere can no longer be readily mixed into deeper waters, limiting natural oxygen replenishment.
Oxygen in the deep water is gradually consumed by aquatic organisms and decomposition processes, causing concentrations to decline.
If stratification begins earlier and persists longer, oxygen depletion may also begin earlier and become more severe later in the season, reducing suitable deep-water habitat.
Reduced oxygen near bottom sediments can increase internal phosphorus release, providing nutrients that may support algae and cyanobacteria growth.
At present, there is no indication of problematic oxygen depletion. In fact, the June 12 dissolved oxygen profile was stronger than the comparable profile from 2025 at every measured depth. However, the combination of warmer surface temperatures, lower lake levels, and earlier stratification suggests that continued monitoring of deep-water oxygen conditions will be particularly important during July and August.
Key Takeaways
✓ Water clarity improved and remains good for mid-June.
✓ Dissolved oxygen is stronger than at the same time in 2025 at all measured depths.
✓ The lake is approximately 1.5 feet lower and surface waters are 4°C (7°F) warmer than during the comparable period in 2025.
✓ Thermal stratification has developed earlier and more strongly than last year.
✓ Deep-water oxygen remains adequate, but earlier stratification could lead to earlier oxygen depletion and increased potential for internal phosphorus release later in the summer.
✓ Overall, the June 12, 2026 data indicate good water quality conditions with improving clarity, strong oxygen availability, and no immediate concerns, while highlighting the importance of tracking oxygen trends through the remainder of the summer season.
Secchi Disc Transparency
Secchi Disk Transparency
The June 12, 2026 Secchi depth was 3.14 meters (10.3 feet).
This reading represents an improvement from the May 29, 2026 measurement of 2.88 meters, reversing the decline observed earlier in the spring. Water clarity is now essentially identical to the June 15, 2025 reading of 3.14 meters .
Key observations:
Clarity improved by approximately 0.26 meters (0.9 feet) since May 29.
Transparency is nearly identical to mid-June 2025.
Current clarity remains consistent with healthy early-summer conditions.
Temperature and Dissolved Oxygen
Temperature Profile
Surface water temperature reached 23.7°C (74.7°F), compared to 19.7°C (67.5°F) on approximately the same date in 2025. The lake has warmed rapidly over the past two weeks and now shows a well-developed thermal structure.
Key observations:
Surface waters are approximately 4°C (7.2°F) warmer than 2025.
Temperatures decline from 23.7°C (74.7°F) at the surface to 15.2°C (59.4°F) at 11 meters (36.1 feet).
The strongest temperature gradient occurs between approximately 2 and 6 meters (6.6 and 19.7 feet), indicating development of the seasonal thermocline.
Deep-water temperatures remain cool at approximately 15.2–16.8°C (59.4–62.2°F) below 6 meters (19.7 feet).
Compared to 2025, the upper few meters (0–2 meters; 0–6.6 feet) are substantially warmer, while temperatures below about 4–5 meters (13.1–16.4 feet) are actually slightly cooler than last year, indicating stronger stratification and less vertical mixing.
Dissolved Oxygen Profile
Dissolved oxygen remained relatively high throughout the water column, ranging from 9.9 mg/L near the surface to 5.9 mg/L at 11 meters (36 feet).
Average dissolved oxygen was 7.83 mg/L, compared to 6.68 mg/L at a similar time in 2025.
Key observations:
Oxygen concentrations exceed 5 mg/L throughout the measured profile.
The lowest reading was 5.9 mg/L at 11 meters, still suitable for most aquatic life.
Average dissolved oxygen was approximately 1.2 mg/L higher than 2025.
Every depth measured showed higher oxygen levels than the corresponding 2025 reading.
This is a notably stronger oxygen profile than observed at the same time last year.
May 29th 2026 Water Quality Report
Overall Summary
Water quality monitoring on May 29, 2026 indicates that Unity Pond remains in generally good condition, but several early-season trends warrant close attention. Water temperatures were approximately 2.2°C (4°F) warmer than at the same time in 2025, and the first signs of thermal stratification are developing. Dissolved oxygen levels remain suitable for fish and aquatic life throughout the water column, but concentrations were lower than those measured one year ago, particularly in deeper water.
The combination of warmer temperatures, emerging stratification, and reduced deep-water oxygen this early in the season is somewhat concerning. These conditions suggest that deep-water oxygen reserves may begin declining sooner than they did in 2025. Continued monitoring will be important as summer progresses, since persistent stratification can lead to oxygen depletion in the deepest waters and increased phosphorus release from bottom sediments, both of which can contribute to algae growth and reduced water quality later in the season.
Secchi Disc Reading
Secchi Disk Clarity
The May 29, 2026 Secchi disk reading was 2.88 meters (9.4 feet), a decrease from 3.19 meters (10.5 feet) measured on May 15. While water clarity declined during the two-week period, the reading remains very similar to late-May conditions observed in both 2024 and 2025. Such changes are common during spring as warming temperatures, biological activity, and changing weather conditions influence water transparency. Overall, water clarity remains within the normal range for this time of year on Unity Pond.
Temperature and Dissolved Oxygen
Temperature Summary
Water temperatures on May 29, 2026 were warmer than on May 30, 2025 throughout the water column. Surface temperature measured 17.5°C (63.5°F), and the lake averaged 16.3°C (61.3°F), about 2.2°C warmer than the previous year. A weak thermocline is beginning to develop between approximately 8 and 10 meters (26–33 feet), indicating the early stages of seasonal stratification.
Key Point: Unity Pond is warming faster than it did in 2025, and stratification is beginning to form. As stratification strengthens, mixing between surface and deep waters will decrease, affecting oxygen conditions at depth.
DO Summary
Dissolved oxygen levels on May 29, 2026 remained adequate throughout the water column, ranging from 9.5 mg/L at the surface to 6.1 mg/L at 12 meters (39 feet). These levels continue to provide suitable habitat for fish and other aquatic life. However, dissolved oxygen concentrations were lower than those measured on May 30, 2025 at every depth, with the greatest reductions occurring in deeper water. Average dissolved oxygen measured 8.33 mg/L, compared to 10.25 mg/L one year earlier.
Key Point: While dissolved oxygen remains at healthy levels throughout Unity Pond, it is somewhat concerning to see lower oxygen concentrations this early in the season. The warmer water temperatures and emerging stratification suggest that deep-water oxygen reserves may begin declining sooner than they did in 2025. As stratification strengthens and persists through the summer, oxygen depletion in the deepest waters and phosphorus release from bottom sediments could occur earlier and more extensively than in recent years.
May 15th 2026 Water Quality Report
Water quality monitoring on Unity Pond/Lake Winnecook on May 15, 2026 showed good early-season conditions. Secchi disk clarity measured 3.19 meters (10.5 feet), indicating relatively clear water for mid-May. Water temperatures were cool and fairly consistent through the water column, showing that the lake is still well mixed in spring conditions. Dissolved oxygen levels were also strong from surface to bottom, remaining around 9 mg/L or higher throughout most depths, which is favorable for fish and aquatic life. Overall, the data suggest healthy spring water quality with good oxygen distribution and moderate clarity.
Secchi Disc Reading
Secchi Disc: The Secchi Disk reading of 3.19 meters (10.5 feet) shows a slight improvement in water clarity compared to May 16, 2025 (3.10 meters), although it remains below the clearer conditions measured on May 16, 2024 (3.63 meters). While it is still too early in the season to identify a meaningful trend, the next several readings will be important in determining whether water clarity stabilizes, improves, or declines as the lake warms and biological activity increases through late spring and early summer.
Temperature and Dissolved Oxygen
Temperature: Water temperature profiles on May 15, 2026 remained relatively uniform with depth, indicating that spring mixing conditions are still largely intact and strong thermal stratification had not yet developed. Average water temperatures were approximately 1.3°C cooler than during the same period in 2025, which is a positive. Average temperature is 12.8 C - 55.0 F
Dissolved Oxygen: Dissolved oxygen concentrations remain relatively consistent throughout the water column, with only modest decreases at greater depths. Average dissolved oxygen levels were approximately 0.7 mg/L lower than the same period in 2025, but concentrations remained at healthy levels across all measured depths.
May 1st, 2026 Water Quality Report
The May 1 reading came in at an encouragingly clear4.01 m (13.2 ft).
For reference, here is early-season data for three years.
Due to high winds on the morning of May 1, we were unable to obtain reliable dissolved oxygen (DO) and temperature readings at depth. Surface dissolved oxygen levels were high - consistent with well oxygenated spring conditions - and temperature readings aligned with seasonal norms.
Surface readings:
DO: 11.1 mg/L (near saturation)
Temp: 10.9°C (51.6°F)
We’re off to a positive start with water clarity!
Past years Water Quality data is below.
Water Clarity UPDATE – Unity Pond (Secchi Depth in Meters)
Current Reading 9/19/2025 - 2.79 m
Clarity Trend - Improving over the last 4 Weeks
Aug 22: Clarity was at its lowest point of the season at 1.39 m, well below the 2.0 m threshold. Conditions at this time were highly impaired and consistent with a bloom.
Sept 5: A significant rebound occurred, with clarity improving to 2.33 m. This represented the first return above the impairment line since late July.
Sept 19: Clarity continued to strengthen, reaching 2.79 m.
2025 Temperature Profile
FOLW Temp Summary — Unity Pond 2025
Surface temperatures rose from ~55 °F in early May to the mid-70s by late July, then cooled to near 68 °F in September.
The mixed layer extended to about 15 ft by midsummer.
A thermocline developed from 15–25 ft in June and persisted through August with sharp gradients.
Deep water below 30 ft remained stable near 52–54 °F all season.
Key Point: Strong stratification prevented oxygen mixing to the bottom, setting up hypolimnetic depletion and nutrient release that can fuel blooms during turnover.
2025 Dissolved Oxygen (DO)
Unity Pond Dissolved Oxygen – 2025 Season Summary
Throughout the summer, Unity Pond showed the classic pattern of oxygen loss in the deeper waters:
Spring (May–June): Oxygen levels were healthy from top to bottom, above 8–10 mg/L, supporting fish throughout the lake (down to 12 m / ~40 ft).
Mid-Summer (July–August): As the lake became layered, the bottom waters (below ~7 m / 23 ft) lost oxygen rapidly. By July, deep areas dropped to near-zero, leaving fish habitat limited to the upper 0–6 m (0–20 ft).
Late Summer (August): The oxygen “dead zone” at the bottom persisted, while surface waters stayed well-oxygenated.
September Turnover: By September 19, the lake began mixing. This turnover brought low-oxygen deep water upward, causing oxygen levels to fall throughout the water column (surface DO dropped below 8 mg/L).
Why this matters
During turnover, nutrients that had built up in the oxygen-poor bottom water were released into the surface. This mixing may explain the cyanobacteria sightings reported September 18th, when short-lived green patches appeared on the pond.
Water Clarity UPDATE – Unity Pond (Secchi Depth in Meters)
Current Reading 9/5/2025 - 2.33 m
Best clarity: ~3.4 m (~11.2 ft) in mid-June
Lowest clarity: ~1.39 m (~4.6 ft) on Aug 8 & Aug 22
Recent trend: Water clarity dropped sharply in July, reached a low in early August, but recovered earlier than in 2024, climbing back to ~2.33 m (~7.6 ft) by Sept 5
Key Point: The midsummer bloom reoccurred, but 2025 rebounded more quickly, likely aided by cooler August nights (mean temp ~1.2 °F lower than 2024), limited rainfall (~1.7" vs. ~3" normal), and early September mixing.
9/5/2025 Temperature Profile Update
FOLW Temperature Summary (9/5/2025)
Surface Temperature: ~70 °F, cooling steadily since mid August
Mixed Layer Extent: From surface down to ~26 ft
Thermocline Range: Between ~26 ft and ~33 ft, where temperature drops rapidly
Deep Water Stability: Below ~33 ft, temperatures remain stable around 61 to 62 °F
Key Point:
The lake remains moderately stratified, but signs of early September mixing are appearing, helping blend some mid-depth waters and setting up conditions for oxygen recovery at depth.
9/5/2025 Dissolved Oxygen (DO) Update
FOLW DO Summary (2025)
Upper Layer (0–13 ft): Oxygen levels stayed strong all season, generally 7–10 mg/L, providing good habitat for fish and aquatic life.
Mid-Depth (16–23 ft): Oxygen depletion began by mid-July, dropping as low as ~2.7 mg/L at 20 ft. Recovery started by late August, rising back above 6 mg/L.
Deep Layer (26–39 ft): Severe hypoxia (<1 mg/L) developed from mid-July through mid-August. By Sept 5, oxygen levels rebounded significantly (up to ~6.1 mg/L at 26 ft), showing early signs of fall mixing.
Key Point:
A prolonged midsummer oxygen deficit created an environment supporting an internal phosphorus release. However, earlier September mixing in 2025 is restoring oxygen more quickly, which helped drive the faster Secchi rebound and may limit late-season algal growth compared to 2024.
Water Clarity UPDATE – Unity Pond (Secchi Depth in Meters)
Current Reading 8/22/2025 - 1.39 m
Best clarity: ~3.4 m (~11.2 ft) in mid-June
Lowest clarity: ~1.39 m (~4.6 ft) on Aug 8 & Aug 22
Recent trend: Water clarity declined significantly from June to early August.
Key Point: Reduced Secchi depth indicates increased algal growth and reduced light penetration, consistent with the warm surface temps and declining oxygen at depth.
8/22/2025 Temperature Profile Update
FOLW Temperature Summary (8/22/2025)
Surface Temperature: ~72.3 °F, cooling from last week
Mixed Layer Extent: From surface down to ~26 ft
Thermocline Range: Between ~26 ft and ~33 ft, where temperature drops rapidly
Deep Water Stability: Below ~33 ft, temperatures remain stable around 59 to 60 °F
Key Point:
The lake remains strongly stratified, preventing mixing between the warm, oxygen-rich upper waters and the colder deep waters.
8/22/2025 Dissolved Oxygen (DO) Update
Dissolved Oxygen (DO) Summary (8/22/2025)
Upper Layer (0–10 ft): ~7.7 mg/L — healthy oxygen levels
Mid-Depth Layer (10–20 ft): ~6.9 mg/L — moderately well-oxygenated
Deep Layer (>26 ft): ~0.8 mg/L — Very low oxygen - anoxic conditions
Key Point:
We have improved DO readings at the 20 to 23 ft levels with the positive effects of wind and wave action. Because of strong stratification, oxygen replenishment from surface waters is not reaching the lower depths. Deep waters remain oxygen-depleted, increasing the risk of phosphorus release from sediments — a process that can fuel algal blooms as mixing occurs later in the fall.
Water Clarity UPDATE – Unity Pond (Secchi Depth in Meters)
Current reading (Aug 8, 2025): 1.39m, the seasonal low.
Trend: Water clarity in 2025 continues to be lower than 2024 for nearly all dates since May 16.
Comparison to 2024: On the same date last year (closest comparable – Aug 7, 2024), clarity was 1.93 m, meaning this year’s clarity is about 25% lower.
Implication: Conditions indicate a sustained bloom period, with visibility well below the 2.0 m threshold used to define significant algal bloom conditions.
Outlook: Unless weather or mixing events occur, clarity is likely to remain low through mid-to-late August before any improvement.
8/8/2025 Temperature Profile Update
Temperature Profile Summary – FOLW Temp Chart (Aug 8, 2025)
Key Point: Strong summer stratification is in place, preventing the mixing of oxygen from the upper layers with the lower layer. This isolation contributes to oxygen depletion in deep water and increases the likelihood of internal phosphorus loading and resulting Algal Bloom.
8/8/2025 Dissolved Oxygen (DO) Update
Dissolved Oxygen Summary – FOLW DO Chart (Aug 8, 2025)
Upper Layer (0–20 ft): Healthy oxygen levels (≥5 mg/L), suitable for fish and aquatic life.
Mid-Depth (23–26 ft): Severe oxygen depletion (<2.5 mg/L).
Deep Layer (>26 ft): Near-anoxic conditions (~1 mg/L or less).
Key Point:
With no mixing, oxygen cannot reach the lower layers, leading to hypolimnetic (Lower Level) oxygen depletion. Low oxygen at the sediment-water interface can cause phosphorus to be released from sediments, fueling algal blooms.
As of July 26, 2025, the Secchi disk reading dropped to 1.88 meters (6.2 feet)—a clear indication of an algal bloom now underway in Unity Pond.
Readings below 2 meters (the dotted red line) indicate a bloom
Lake Temperature Trends – Spring to Summer 2025
Lake Temperature Trends – Spring to Summer 2025
From early May through late July 2025, Unity Pond experienced steady warming of surface and deeper waters. Surface temperatures (0 meters) rose from 13.2°C (55.8°F) on May 3 to 24.5°C (76.1°F) by July 26. At 6 meters, temperatures increased from 11.1°C (52.0°F) to 20.9°C (69.6°F), showing significant warming well below the surface.
Key observations:
Thermal stratification — the layering of warm water over cooler, deeper water — was well established by mid-June.
Temperatures exceeded 20°C (68°F) at depths down to 5–6 meters by late July, limiting mixing and oxygen distribution.
These stagnant, warm conditions set the stage for harmful algal blooms, which thrive in such environments.
Continuous monitoring of temperature patterns supports water quality management and bloom forecasting.
Dissolved Oxygen (DO) Levels – Spring to Summer 2025
Dissolved Oxygen (DO) Levels – Spring to Summer 2025
Oxygen levels in Unity Pond remained high and well-distributed throughout the water column in early spring, with concentrations around 10 mg/L at all depths. However, as surface temperatures rose and the lake stratified:
Oxygen began to decline rapidly below 6 meters, starting in mid-June.
By early July, DO levels fell to hypoxic conditions (below 2 mg/L) at depths greater than 7 meters.
By late July, oxygen was nearly depleted (≤1 mg/L) at depths 9 meters and deeper, creating anoxic conditions in bottom waters.
These changes can lead to the release of nutrients from sediments and promote harmful algal blooms.
Secchi Disc Update 6/27/2025
My apologies to those who attended the Let’s Make it Clean Not Green meeting on June 26, 2025. I incorrectly reported the June 15 Secchi reading as 3.41 meters; the correct reading was 3.14 meters.
The latest Secchi Disc reading taken on June 27, 2025, shows 3.40 meters (approximately 11 feet), indicating an improvement in water clarity.
Temperature Update
The lake continues to warm, and the surface temperature of the lake has increased by 1°C compared to the same time last year. While we've experienced a few hot days with temperatures over 90°F, we've also had some cool nights dipping into the low 50s. The lake is warming, but on average the temperature increase is only 0.1°C compared to last year for the.
Please note: Temperature readings at the 12-meter (39.4 ft) depth are no longer being recorded, as the lake’s depth has dropped to 37.6 ft at the Midas Point—the deepest location in the lake.
Here are the 6/27/2025 temperatures readings with depth converted from meters to feet and temp converted from C to F.
Dissolved Oxygen (DO) Update
Dissolved Oxygen (DO) levels continue a gradual seasonal decline as expected (warmer water holds less oxygen) but encouragingly remain higher this year compared to the same period last year.
On June 27, 2025, DO readings at the 9, 10, and 11-meter depths are above 1.0 mg/L, which is an improvement. In 2024, these same depths had already dropped to 1.0 mg/L or below, a condition known as anoxia—where oxygen levels are too low to support most aquatic life. This is critical because when DO levels fall below 1 mg/L, phosphorus bound to iron in lakebed sediments is released into the water column. This "internal loading" of phosphorus acts like fertilizer and can fuel algae blooms.
The key takeaway:
DO above 1 mg/L at the lake bottom slows phosphorus release from sediments.
Why This Matters
DO < 1 mg/L = Anoxia = Phosphorus Release from Iron in lake bottom sediment
DO > 1 mg/L = Less Internal Phosphorus Loading
This is where Alum Treatment plays a vital role. Unlike iron, aluminum binds to phosphorus in a stable form, even under anoxic conditions. So, even as DO drops later in the season, the phosphorus remains locked up, reducing the risk of algal blooms.
Water temperature significantly impacts lake water quality by affecting the amount of dissolved oxygen, nutrient levels, stratification patterns, and the growth of algae and other aquatic organisms, with warmer temperatures generally leading to decreased dissolved oxygen, increased algal blooms, and potential disruption of the ecosystem balance, ultimately impacting the overall health of the lake
Water Temperature readings for 2024
Dissolved Oxygen readings for 2024
Dissolved oxygen (DO) is crucial to a lake's health because it is essential for the survival of all aquatic organisms, including fish, plants, and invertebrates, as they need oxygen to breathe, making it a key indicator of water quality and the ability of a lake to support life; low DO levels (below 2.0 mg/l) can lead to stress, disease, and even fish kills if significantly depleted
Microcystins
Microcystins are a family of toxins produced by cyanobacteria, a type of blue-green algae, that can cause serious illness in humans and death in animals
Friends of Lake Winnecook tested for Microcystins in 2023 and 2024, the results were negative for the presence of Microcystins.
Secchi Disk
A Secchi Disc Reading is recorded when the Disc is no longer visible
