Issue 5

Key Findings From Coweeta

The Impacts of Forest Management on Water Quality and Quanitity

The amount of water flowing from a forest watershed increases after timber harvest, mainly because of reduced transpiration from trees.

The volume of water from storms (stormflow) and maximum peak flows also tend to increase after harvest.

Water yields and changes in stormflow lessen as vegetation grows back.

Increases in the concentrations of nutrients such as nitrogen and phosphorus tend to be short lived.

Leaving stream management zones—buffer strips of uncut trees and shrubs—protects stream temperatures by providing shade.

Though erosion and sedimentation from forest management activities is small compared to other land uses, it can be significantly higher than that on undisturbed forest watersheds.

Natural disturbances such as insect outbreaks can also temporarily increase nutrient losses from forest watersheds.

Poorly designed or maintained roads are the main source for increased sediment levels associated with forest activities. Streamside management zones of sufficient width and extent are critical for reducing the delivery of pollutants to streams.

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