| Water body | 1952-1970 | 1970-2000 | 2000-2012 | |||
| PLNV | SD | PLNV | SD | PLNV | SD | |
| Namakan Reservoir | 0.71 | 0.32 | 0.54 | 0.27 | 0.72 | 0.24 |
| Rainy Lake | 0.82 | 0.19 | 0.89 | 0.14 | 0.72 | 0.30 |