FOREST HARVESTING AND WATER: THE LAKE STATES EXPERIENCE1

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Abstract
The impact of forests on water has‐been a subject of argument for more than a century. It still is; and many studies conform that there is no single right answer in the debate. In the Lake States, clearcutting natural peatlands will not change annual stream‐flow nor will it seriously impact water quality if logging is done on frozen soils. However, clearcutting will cause water tables to fluctuate more, ranging from 9 cm higher to 19 cm lower than in peatlands with mature forests. Clearcutting upland hardwoods or conifers will increase annual strearnflow by 9to20 cm (a 30‐to80‐percent increase). Streamfiow returns to preharvest levels in 12 to 15 years. Annual peak flows are at least doubled and snowmelt flood‐peak increases may persist for 15 years. Water quality is not widely impacted, but operating logging equipment in stream channels will cause channel clogging by filamentous algae and loss of fish habitat. Permanent changes from forest to agricultural and urban land use on two‐thirds or more of a watershed will significantly increase the size of flood peaks in the 2‐ to 30‐year return interval storm or snowmelt.