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A handful of studies have modeled hydrologic response to climate change in the Southeast using scenarios based on GCMs or other projections. The scenarios used in these studies consistently project warming by the end of the 21st century (although vary in magnitude) but differ in the projected chang- es in precipitation patterns, with some scenarios projecting decreases and others projecting increases in annual precipitation. A regional assessment of the effects of climate change on forest productivity and hydrology suggested that climate change could significantly alter stream flow across many forested areas in the southern U.S. (McNulty et al. 1997). The studies reviewed here (see Box 2 -2) are limited to forested systems in the coastal plain. However, a common finding was that hydrologic regimes are likely to be much more sensitive to changes in precipitation than to changes in temperature. Box 2 -2. Hydrological models applied at watershed and regional scales in the southeast. Sun et al. (2000) looked at climate change impacts on the hydrology and productivity of loblolly pines using PnET -IIS on a flat lower coastal plain in North Carolina. The PnET -IIS model closely integrates forest hydrology with biological processes, however, like most other models reviewed here, it does not consider biological responses such as stomata conductance and water use efficiency to changes in temperature and carbon dioxide concentra- tions. Under a climate scenario projecting warmer temperatures and increased precipitation (HadCM2), forest productivity, evapotranspiration, and drainage were all projected to increase, suggesting that overall water yield will track trends in precipitation patterns. Amatya et al. (2006) used DRAINWAT to reassess climate change impacts on drainage and shallow groundwater tables in a loblolly pine plantation in North Carolina. Unlike the PnET-IIS model, DRAINWAT is based on a model developed for use with poorly drained soils. Amataya et al. (2006) examined two future climatic scenarios repre- senting warmer /wetter (HadCM2) and hotter /drier (CGC1) regimes projected over a 25 -year period. The results of both climate scenarios indicated that the change in air temperature would have a less significant impact than the change in precipitation on the hydrology of the system. In both scenarios, evapotranspiration increased. However, there was little effect on the drainage outflows under the HadCM2 climate scenario (5% increased precipitation). Under the CGC1 scenario (12% decreased precipitation) decreased outflow was the result of reduced rain and deeper predicted water table depths. Even under these conditions, water was not limited enough to significantly reduce forest productivity. Lu et al. (2006) applied the MIKE SHE model to a coastal plain watershed in South Carolina. The MIKE SHE model simulates the full hydrologic cycle characteristics of forest ecosystems, including evapotranspiration and verti- cal soil water movement in the unsaturated zone to the groundwater. They looked at response to increased air temperature or decreased precipitation independently using fixed scenarios rather than inputfrom GCMs. Warmer temperatures (2 °C) or decreased precipitation (10 %) resulted in reduced groundwater recharge and thus a lower water table. Similarly, projected stream flow decreased in response to warmer temperatures or reduced precipi- tation. However, stream flow was much more sensitive to changes in precipitation than temperature. Qi et al. (2009) found similar results using the USGS Precipitation Runoff Modeling system model with downscaled GCMs to examine the potential impacts of climate on the monthly stream flow of a river basin on the lower coastal plain of eastern North Carolina. Simulated stream flow response was more sensitive to changes in precipitation than to air temperature using scenarios based on the HadCM2 and CGC1.