Shoal Lake Water Quality Trend
Itasca County, Minnesota · 2020–2024 · 5 years of data
Shoal Lake water quality has been stable over the 5-year window from 2020–2024, based on EPA Water Quality Portal samples. The lake holds an overall Grade C today.
Water Clarity (Secchi)
→ StablePhosphorus
Insufficient data (0 years, need 4+).
Chlorophyll-a
Insufficient data (0 years, need 4+).
How to read this
- Clarity (Secchi depth): deeper visibility is better. An upward line means the water is getting clearer.
- Phosphorus & Chlorophyll-a: lower is better. A downward line means fewer nutrients fueling algae growth.
- Year-to-year variability is normal. Weather, sample timing, and short-window data all add noise. Look at direction, not single-year jumps.
Methodology
Each metric is calculated from EPA Water Quality Portal samples. Annual values are the median of all samples taken that year. The trend direction comes from a linear regression of those annual medians; we classify it as improving, declining, or stable when the change-per-year is below 2% of the long-run mean. The current cache spans roughly 2020–2024, which is a short window for climate-scale claims. Use this page to spot direction and as a launch point — link out to the EPA WQP for the raw record before citing as evidence.