Missouri vs Illinois, Lake Water Quality Comparison
A data-driven comparison of lake water quality between Missouri and Illinois, built from EPA Water Quality Portal monitoring data.
| Missouri | Illinois | |
|---|---|---|
| Total Lakes | 278 | 148 |
| Average Grade | C | D |
| Average Score | 1.81 | 0.99 |
| Grade A Lakes | 51 | 9 |
| Grade B Lakes | 11 | 9 |
| Grade C Lakes | 55 | 6 |
| Grade D Lakes | 44 | 20 |
| Grade F Lakes | 55 | 52 |
| Oligotrophic (Cleanest) | 17 | 0 |
| Eutrophic (High Nutrient) | 99 | 35 |
| Lakes with Invasives | 13 | 7 |
| Improving Trend | 89 | 10 |
| Declining Trend | 92 | 7 |
Analysis
Missouri has 278 graded lakes averaging a C (score 1.81), while Illinois has 148 graded lakes averaging a D (score 0.99). On average water quality, Missouri comes out ahead.Missouri counts 51 Grade A lakes and 17 oligotrophic (clearest-class) lakes, against 9 and 0 for Illinois.
Long-term monitoring shows 89 improving and 92 declining lakes in Missouri, versus 10 improving and 7 declining in Illinois. Dataset coverage varies by state: Missouri has maximum-depth data for 0 lakes and documented fish species on 0, compared with 0 and 0 for Illinois. Where a figure is zero, that state dataset has not yet been ingested — grades there rest on EPA clarity and nutrient measurements alone.
Frequently Asked Questions
Does Missouri or Illinois have cleaner lakes?
Missouri has an average lake grade of C (score 1.81) while Illinois averages D (score 0.99). Missouri has the better average water quality. Grades are computed from EPA Water Quality Portal clarity and nutrient measurements.
Which state has more graded lakes?
Missouri has 278 graded lakes while Illinois has 148. Counts reflect lakes with enough EPA Water Quality Portal monitoring data to grade, not the total number of lakes in each state.