Water scarcity in the Southeastern U.S. has increased in recent decades due to rapid population growth, land use intensification, and climate variability. Streams that normally experience reduced flows in summer now frequently run dry and the frequency of stream drying is expected to increase in the future. Future water-centric land management, especially restoration of native longleaf pine, may have some potential in helping to mitigate water scarcity in the region. We used the Soil and Water Assessment Tool (SWAT) to examine the potential effects of future land cover change scenarios on streamflow in the Ichawaynochaway Creek, part of the Lower Flint Basin (Georgia, USA). The SWAT model is a semi-distributed, runoff based model that uses weather, land use, elevation, and soils as inputs in order to simulate river discharge and loadings of nutrients, sediment, bacteria, and pesticides. The model was calibrated for average monthly flow at two USGS sites (Ichawaynochaway Creek at Milford and below Newton) from 2007-2015. We then ran a number of land cover change scenarios that included changing cover type (e.g. reduced agricultural cover, increased hardwood forest cover, and increased longleaf pine forest cover) as well as increasing irrigation efficiency, and reducing irrigation.
Results/Conclusions
Model calibration resulted in Nash-Sutcliffe efficiency of 0.85, r2= 0.86, and a percentage bias of -6.3% at the watershed outlet. Converting all agriculture and pasture land cover in the watershed to hardwood forest cover decreased average discharge 16.2%. However, converting the same lands in the watershed to all pine cover increased average discharge 13.7%. While these results are preliminary, they indicate that the SWAT model can be used successfully to assess the effects of land cover change on changes in the magnitude and direction of stream discharge in this watershed. These results also indicate that forest restoration activities that focus on species with higher water use efficiency can improve stream discharge. Because large-scale reforestation is unlikely throughout the entire watershed, future work will focus on the potential of longleaf pine restoration to increase discharge in specific, targeted sub-watersheds that have been identified as losing stream reaches during summer droughts. Future results will help managers and policy-makers better assess the full value of ecosystem service derived from longleaf pine restoration.