Modeling the Potential Effects of Forest Management and Climate Change on Water Yield Across the Southeastern U.S.

Forest ecosystems are expected to undergo dramatic structural and area changes in response to projected pressures of timber demands and global climate change in the 21st century. Associated with changes in forest structure and area distribution is forest water yield, which affects water availability for both humans and aquatic ecosystems needs. Diverse forest hydrology conditions exist in the southeastern U.S. due to great differences in climate, vegetation cover types, and land topography/elevation across the region. The objective of this study is to project the potential effects of forest management and climate change on annual water yield at a regional scale. A generalized annual actual evapotranspiration (AET) model was first calibrated with a watershed-scale database derived from 39 forest-dominated watersheds representing the diverse eco-regions of the Southeast. Then, the model was validated at a 0.5*0.5 degree spatial resolution (about 50 *75 km2) across the region using historic hydrology, climate, and landcover data. Finally, the model was applied to the region using the Hadley Centre Had2CMSul climate change scenario for the region. The simple annual time step hydrologic model adequately explained the spatial variability of water yield across the southeastern region. Modeling results suggest that water yield responses to forest removal are diverse across the physiographic gradients with the highest values occurring in the conifer-dominated regions. The model predicted water yield increases as high as 450 mm/yr as a result of complete forest removal. The Had2CMSul predicts the southeaster