On the Sacandaga River watershed above Hope, New York, a slow one-directional change in land use and an increase in forest cover have been correlated with a decrease in average annual, dormant season, and April runoff over the 39-year period from 1912 to 1950. In 1912, total forest stand density and the density of conifers on the watershed were probably as low as they had ever been, after widespread logging, insect attacks, and a series of fires. As the beaver population increased explosively from 10 individuals to 20,000 individuals and forest density and crown cover of conifers increased up to 1950, the average annual streamflow decreased 7.72 inches, largely as a result of a 5.18-inch decrease in dormant season runoff. April was the only month showing a large enough decrease in runoff (2.98 inches) to be statistically significant. Also, the average length of time it took for the most concentrated one-half of the annual streamflow to run off increased by 19 days, from 67 to 86 days. The storm of November, 1950, disrupted the associated patterns of forest stand development and streamflow change, returning both to a point nearer their 1912 levels. Continuing mortality of trees weakened or exposed by the storm damage had not permitted the re-establishment of any well defined pattern (by 1962) in either stand development or streamflow, although the changes in quantity and timing of flow parallel the changes in vegetation and largely verify the relationships inferred for the previous period.
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