South Dakota vs North Dakota, Lake Water Quality Comparison
A data-driven comparison of lake water quality between South Dakota and North Dakota, built from EPA Water Quality Portal monitoring data.
| South Dakota | North Dakota | |
|---|---|---|
| Total Lakes | 9 | 149 |
| Average Grade | F | C |
| Average Score | 0 | 1.77 |
| Grade A Lakes | 0 | 3 |
| Grade B Lakes | 0 | 16 |
| Grade C Lakes | 0 | 39 |
| Grade D Lakes | 0 | 23 |
| Grade F Lakes | 2 | 10 |
| Oligotrophic (Cleanest) | 0 | 1 |
| Eutrophic (High Nutrient) | 0 | 55 |
| Lakes with Invasives | 0 | 8 |
| Improving Trend | 0 | 21 |
| Declining Trend | 1 | 32 |
Analysis
South Dakota has 9 graded lakes averaging a F (score 0), while North Dakota has 149 graded lakes averaging a C (score 1.77). On average water quality, North Dakota comes out ahead.South Dakota counts 0 Grade A lakes and 0 oligotrophic (clearest-class) lakes, against 3 and 1 for North Dakota.
Long-term monitoring shows 0 improving and 1 declining lakes in South Dakota, versus 21 improving and 32 declining in North Dakota. Dataset coverage varies by state: South Dakota has maximum-depth data for 0 lakes and documented fish species on 0, compared with 0 and 0 for North Dakota. 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 South Dakota or North Dakota have cleaner lakes?
South Dakota has an average lake grade of F (score 0) while North Dakota averages C (score 1.77). North Dakota has the better average water quality. Grades are computed from EPA Water Quality Portal clarity and nutrient measurements.
Which state has more graded lakes?
South Dakota has 9 graded lakes while North Dakota has 149. Counts reflect lakes with enough EPA Water Quality Portal monitoring data to grade, not the total number of lakes in each state.