We found 44 public water systems in Monona county (ordered by population size).
| Name | Areas served | Population served | Contaminant count | Violation count |
|---|---|---|---|---|
| Onawa Municipal Water Plant | Onawa | 3,008 | 0 | 1 |
| Mapleton Municipal Water Plant | Mapleton | 1,224 | 0 | 20 |
| Casino Omaha Water System | Onawa | 1,000 | 0 | 0 |
| Whiting Water Supply | Whiting | 762 | 0 | 3 |
| Ute Water Supply | Ute | 379 | 0 | 11 |
| Onawa Koa | Onawa | 302 | 0 | 5 |
| Timber Ridge Lodge Recreation, Ltd. | Castana | 250 | 0 | 7 |
| Dot-3 (i-29 Ra 028e Onawa) | Onawa | 237 | 0 | 0 |
| Moorhead Water Supply | Moorhead | 226 | 0 | 22 |
| Blencoe Municipal Waterworks | Blencoe | 224 | 0 | 20 |
| Dot-3 (i-29 Ra 027w Onawa) | Onawa | 205 | 0 | 0 |
| Soldier Water Supply | Soldier | 174 | 0 | 15 |
| Castana Municipal Water Supply | Castana | 147 | 0 | 49 |
| First Christian Church Camp | County of Monona | 130 | 0 | 0 |
| Interchange Service Corp | Onawa | 120 | 0 | 0 |
| YELLOW ROSE | County of Monona | 104 | 0 | 0 |
| Dwight's Skelly | County of Monona | 100 | 0 | 0 |
| Robert Mcfarland | County of Monona | 80 | 0 | 0 |
| Rodney Water Supply | Rodney | 74 | 0 | 0 |
| Lewis And Clark State Park | Onawa | 67 | 0 | 0 |
| Linda's Cafe | County of Monona | 63 | 0 | 0 |
| Frog Pond Cafe | County of Monona | 60 | 0 | 0 |
| Turin Head Start | County of Monona | 54 | 0 | 0 |
| Jesco's Stkhse Lng | County of Monona | 54 | 0 | 0 |
| The Office Tavern | County of Monona | 50 | 0 | 0 |
| Onawa Country Club | Onawa | 50 | 0 | 0 |
| Divide Hill Bar & Grill | Castana | 50 | 0 | 0 |
| The Bank | County of Monona | 50 | 0 | 0 |
| Camp Onawa | County of Monona | 50 | 0 | 0 |
| Ticonic Methodist Church | County of Monona | 40 | 0 | 0 |
| Reds Turin Inn | County of Monona | 40 | 0 | 0 |
| Mcdonald Tavern | County of Monona | 40 | 0 | 0 |
| United Christ Church | County of Monona | 35 | 0 | 0 |
| Lighthouse Marina | Whiting | 30 | 0 | 0 |
| Huff-warner Acc-monona Conserv | County of Monona | 25 | 0 | 0 |
| Broer's Conoco | County of Monona | 25 | 0 | 0 |
| Leachollow Inn | County of Monona | 25 | 0 | 0 |
| Decatur Bend Acc-monona Conser | County of Monona | 25 | 0 | 0 |
| Monona Arboretum-monona Conser | County of Monona | 25 | 0 | 0 |
| Oldham Rec Ar-monona Conservat | County of Monona | 25 | 0 | 0 |
| Whiting Wds-monona Conservatio | County of Monona | 25 | 0 | 0 |
| Loess Inn | County of Monona | 25 | 0 | 0 |
| Preparation Canyon State Park | County of Monona | 25 | 0 | 0 |
| The Country Inn | County of Monona | 25 | 0 | 0 |