Hello Matthews Lake Neighbors,
As we settle into the peak of summer and enjoy long, sunny days out on the water, it is the perfect time to check in on the overall health of our lake. Following up on our spring baseline testing, our first of three summer water samples were collected on June 29, 2026, and sent to the Water and Environmental Analysis Lab at UW–Stevens Point to monitor key indicators like algal growth, nutrient levels, and water clarity. Tracking these parameters during the warmer months gives us a clear window into how the lake is holding up under summer conditions and helps us catch any subtle shifts early. Overall, the latest findings bring very good news about our water quality—let’s dive straight into what the numbers tell us about Matthews Lake as we head into July testing.
When reading lab results, the Limit of Detection (LOD) and Limit of Quantitation (LOQ) define how sensitive testing equipment is at detecting trace amounts of a substance. The LOD is the absolute lowest concentration a lab method can detect to confirm that a compound is present, though it cannot be measured with exact numeric precision. The LOQ is a slightly higher threshold—the lowest concentration where the lab can confidently measure the precise amount with high statistical accuracy. Any result below the LOD is reported as “Not Detected” (ND), while a result that falls in the narrow band between the LOD and LOQ is considered a trace estimate (often flagged with a “J” qualifier on lab reports).
🟢 Green Status: Excellent / Healthy
- Total Phosphorus: ND (Not Detected) (Lab Tolerance — LOD: 0.008 mg/L / LOQ: 0.028 mg/L)
- Acceptable / Healthy Range: Less than 0.020 mg/L.
- Note: Phosphorus is the primary fuel for algae blooms. Seeing Total Phosphorus drop from May’s 0.013 mg/L down to “Not Detected” in late June is a good result. It suggests that there is no major runoff loading into the lake as summer heats up.
- Chlorophyll a (non-acidified): 3.9 µg/L (Lab Tolerance — LOD: 0.2 µg/L / LOQ: 0.7 µg/L)
- Acceptable / Healthy Range: Less than 7.0 µg/L represents clear, oligotrophic-to-mesotrophic water. Levels above 10–15 µg/L indicate noticeable green algae growth, while severe blooms usually exceed 20–30 µg/L.
- Note: Chlorophyll a measures the amount of green algae floating in the water column. A reading of 3.9 µg/L confirms that while aquatic life is active in early summer, algae levels remain relatively low and water clarity remains strong.
🟡 Yellow Status: Normal Baseline / Watch
- Nitrate + Nitrite (NO3+NO2): 0.3 mg/L (Lab Tolerance — LOD: 0.1 mg/L / LOQ: 0.5 mg/L)
- Acceptable / Healthy Range: Less than 0.3 mg/L is standard for healthy, unpolluted lakes.
- Note: This represents inorganic nitrogen. Because 0.3 mg/L falls between the LOD (0.1) and LOQ (0.5), it receives a “J” Qualifier flag, meaning the lab detected a real trace amount, but it sits right on the edge of the machine’s precision limit. In May, this was “Not Detected,” so this minor uptick is consistent with normal early-summer plant and soil activity.
- Total Kjeldahl Nitrogen (TKN): 0.54 mg/L (Lab Tolerance — LOD: 0.12 mg/L / LOQ: 0.41 mg/L)
- Acceptable / Healthy Range: Less than 0.60 mg/L for clean, healthy lakes.
- Note: TKN measures organic nitrogen (naturally occurring living and decaying plant matter). It rose slightly from May’s reading of 0.41 mg/L to 0.54 mg/L. References suggest that this gentle seasonal uptick is consistent with normal aquatic plant growth and biological activity increases.
- Total Nitrogen (TKN + NO3 + NO2): 0.840 mg/L (Lab Tolerance — LOD: 0.120 mg/L / LOQ: 0.470 mg/L)
- Acceptable / Healthy Range: Less than 1.0 mg/L.
- Note: This is a calculated total combining organic nitrogen and inorganic nitrates. At 0.840 mg/L, it remains within a healthy baseline, showing that nutrient levels are stable as we head into mid-summer.
Summary Comparison: May vs. June 2026
| Parameter | May 2026 Result | June 2026 Result | Trend / Interpretation |
| Total Phosphorus | 0.013 mg/L | ND (<0.008 mg/L) | 🟢 Improved: Nutrient availability dropped, keeping algae risk very low. |
| Chlorophyll a | Not Sampled | 3.9 µg/L | 🟢 Excellent Baseline: Low floating algae levels. |
| NO3 + NO2 | ND | 0.3 mg/L (Trace – J) | 🟡 Normal: Minor trace increase typical of summer biological activity. |
| Total Kjeldahl Nitrogen | 0.41 mg/L | 0.54 mg/L | 🟡 Normal: Expected seasonal rise as lake plant life grows. |
| Total Nitrogen | Not Calculated | 0.840 mg/L | 🟡 Healthy: Below the 1.0 mg/L threshold. |
Key Takeaways
- No Algae Fuel Surplus: The fact that Total Phosphorus dropped to “Not Detected” in late June is great news. Without excess phosphorus, the lake lacks the primary fuel needed to spark severe blue-green algae blooms during warm July and August days.
- Healthy Seasonal Shift: Nitrogen levels (TKN) naturally crept up slightly from May (0.41 to 0.54 mg/L). The literature suggests that this is completely expected as aquatic plants grow, insects hatch, and biological life peaks in early summer.
- Clean Water Conditions: A Chlorophyll a reading of 3.9 µg/L indicates that water clarity remains in great shape heading into the peak summer recreational season.
While I enjoy diving into these numbers and sharing my perspective as a fellow neighbor, please keep in mind that I’m just a lake enthusiast, not a professional limnologist or water chemist! If you’re curious to learn more about the science behind these indicators or want to explore regional water data in depth, I encourage checking out the excellent resources on the University of Wisconsin–Stevens Point Extension Lakes website or looking through other credible conservation sources. You can access the free University of Wisconsin’s official guide to water quality interpretation directly through the UW-Stevens Point Extension Lakes Data Page or download the Understanding Lake Data PDF directly via UW Extension’s Learning Store.
What the Guide Covers
This publication (Understanding Lake Data, G3582) is the standard reference for interpreting Wisconsin laboratory results. It provides detailed explanations for:
- Nutrients & Clarity: How phosphorus, nitrogen, and chlorophyll a drive trophic status (oligotrophic, mesotrophic, eutrophic).
- General Chemistry: Normal background ranges for pH, alkalinity, hardness, and conductivity across various lake types (seepage vs. drainage).
- Dissolved Minerals & Metals: Typical levels for chloride, sodium, sulfate, calcium, and magnesium.
- Limnology Terminology: A comprehensive glossary of terms used in Wisconsin lake study reports.
Thanks again for your interest and for staying engaged. More next month.
Mike
Historical Trends
