Water scarcity in the southeastern United States has increased in recent decades due to rapid population growth, land use intensification, and climate variability. While precipitation in the region is relatively high (~1300 mm/year), declines in river discharge suggest a growing need to evaluate land management options focused on reducing evapotranspiration and maintaining watershed yield. Restoration of longleaf pine [Pinus palustris Mill. (Pineaceae)] forests, which once dominated the southeastern United States Coastal Plain, represents one possible land management option to restore hydrologic function and help mitigate regional water scarcity. Ichawaynochaway Creek is a major tributary of the lower Flint Basin, which is mostly within the historic range of longleaf pine and has seen interstate conflicts over water appropriations. We used the Soil and Water Assessment Tool (SWAT) to evaluate the potential effect of large-scale longleaf pine restoration on streamflow in the Ichawaynochaway Creek Basin. We modified the default model by adding field-derived plant growth parameters including leaf area index and stomatal conductance for longleaf pine, loblolly pine and mixed oak species. We then simulated the conversion of ~24,000 ha (~32% of basin area) of degraded mixed-species forest to longleaf pine savanna.
Results/Conclusions
Model results confirmed that longleaf pine savanna has the lowest demand for water as evapotranspiration compared to other major vegetated land cover types in the basin. Longleaf pine restoration increased streamflow across a wide range of hydrological conditions by 18 mm, or 53 million m3 annually. The difference is ~20% for upper watershed and ~8% for the entire watershed when compared with original landuse. The impact was most prominent during low flow and low precipitation periods, which increased by as much as 50% for the upper watershed. These changes in stream flow may prove vitally important in maintaining quality in-stream habitat for imperiled aquatic organisms during seasonal droughts and critically dry periods. Large-scale restoration of longleaf pine savanna could help mitigate water scarcity in the Ichawaynochaway Creek Basin and other areas, especially during drought.