Hydrologic Effects

1. Large impoundments can arrest the flow of water.
2. Flow regulation can result in reduced flow during spring freshet and controlled summer discharge. Maintenance of pre-development fish populations has not been achieved in cases where river flows have become regulated.
3. Loss of spring freshets degrades aquatic habitat by inhibiting the annual sediment flush of physical habitats.
4. Reduced flows can strand fish and fry.
5. Culverts and weirs can become velocity barriers, where the current of water moves too quickly for migrating fish.
6. Wide dams and weirs spread water across the top of the spillway; this diffuses the attraction flow, making it difficult for fish to find passage.