Illinois vs Indiana, Lake Water Quality Comparison
A data-driven comparison of lake water quality between Illinois and Indiana, built from EPA Water Quality Portal monitoring data.
| Illinois | Indiana | |
|---|---|---|
| Total Lakes | 148 | 22 |
| Average Grade | D | B |
| Average Score | 0.99 | 2.5 |
| Grade A Lakes | 9 | 0 |
| Grade B Lakes | 9 | 1 |
| Grade C Lakes | 6 | 1 |
| Grade D Lakes | 20 | 0 |
| Grade F Lakes | 52 | 0 |
| Oligotrophic (Cleanest) | 0 | 1 |
| Eutrophic (High Nutrient) | 35 | 0 |
| Lakes with Invasives | 7 | 4 |
| Improving Trend | 10 | 4 |
| Declining Trend | 7 | 8 |
Analysis
Illinois has 148 graded lakes averaging a D (score 0.99), while Indiana has 22 graded lakes averaging a B (score 2.5). On average water quality, Indiana comes out ahead.Illinois counts 9 Grade A lakes and 0 oligotrophic (clearest-class) lakes, against 0 and 1 for Indiana.
Long-term monitoring shows 10 improving and 7 declining lakes in Illinois, versus 4 improving and 8 declining in Indiana. Dataset coverage varies by state: Illinois has maximum-depth data for 0 lakes and documented fish species on 0, compared with 0 and 0 for Indiana. 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 Illinois or Indiana have cleaner lakes?
Illinois has an average lake grade of D (score 0.99) while Indiana averages B (score 2.5). Indiana has the better average water quality. Grades are computed from EPA Water Quality Portal clarity and nutrient measurements.
Which state has more graded lakes?
Illinois has 148 graded lakes while Indiana has 22. Counts reflect lakes with enough EPA Water Quality Portal monitoring data to grade, not the total number of lakes in each state.