| |
Free-flowing River |
Dammed River |
| Temperature |
Natural temperature regime |
Greater surface area of impoundment and surface release often results in higher water temperatures in impoundment and downstream |
| Dissolved oxygen |
Turbulent flow and shallower water depths result in high dissolved oxygen concentration |
Loss of turbulent flow may reduce dissolved oxygen concentration; impoundment may stratify, further reducing dissolved oxygen |
| Habitat |
Riverine coldwater habitat |
Habitat is more lake-like and often unsuitable for coldwater fish species |
| Fish movement |
Fish and other organisms free to move upstream and downstream, including migratory fish such as Atlantic salmon |
Access to habitat blocked or fragmented |
| Flow regime |
Natural flow regime |
Modified flow regime |
| Sediment |
Natural transport processes maintained |
Trapped in impoundment—natural substrate buried by sediment in impoundment, downstream channel erosion may result to “replace” trapped sediment |
| Pollutants |
Metals and organics are distributed downstream |
Metals and organics are concentrated in fine sediments trapped in impoundment |
| Nutrient transport |
Nutrients are transported downstream |
Portion of nutrients trapped in impoundment |
| Woody debris |
Woody debris is transported downstream to create habitat |
Portion of woody debris trapped in impoundment |
Watershed Management Division 
dec calendar 
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