Future water resources in the context of climate and land use change
In the Southeastern US, population growth and urban development are expected to increase over the next several decades. Combined with increased temperatures and more variable precipitation, regional water scarcity is a significant concern. Scenario-based futures are needed to inform policies to increase the resilience of future water resources. We addressed this need by investigating the impacts of land use and climate changes on water resources throughout the Yadkin River (YR) watershed in North Carolina. The YR watershed spans from the mountains to the coast and contains a mix of land uses. We selected three sub-watersheds representative of the physiography and land use across the watershed for detailed analyses, including changes in land use, climate, and stream flow. Current and projected land use meld the National Land Cover Data and U.S. Forest Service Forest Inventory and Analysis Plots. Land use and climate were modeled using 50-year regional climate and socio-economic forecasts for low (B2, CSIRO) and moderately high (A1B, CISRO) rates of development. These forecasts were used to inform RHESSys, a regional eco-hydrological simulation system.
Our projections indicated that land use, climate, and hydrologic changes will vary across the YR watershed. Land use in forest dominated regions of the watershed remained relatively constant, with a 2.5% loss of forest land and a 1% loss of agricultural land under the moderately high scenario and almost no change under low change scenario. In the Piedmont region near urban areas, approximately 8-20% of forested land in both rural and urban watersheds was converted to development. In the Piedmont region near rural areas, 6-8% of the agricultural land was converted to development. RHESSys analyses indicate that even small changes in land use affect streamflow. In the predominately forested watershed, high flows increased under the moderately high change scenario, causing a 4% increase in annual water yield. Both the low and moderately high change scenarios increase high flows and decreased baseflows in the Piedmont watersheds. With reduced ET and higher impervious surface, water yield increased in the developing rural watershed by 35-70% and 11-17% in the urban watershed. Our results suggest that streamflow is sensitive to small changes in land use, but the greatest land use changes and the impacts on hydrology will occur in urban and rural areas adjacent to metropolitan areas.