Responses to Land Use and Climate Change for a Culturally Significant Blackwater Stream

Hydrological modeling can reveal insight about how rainfall becomes streamflow in a watershed comprising heterogeneous soils, terrain and land cover. We applied the Soil & Water Assessment Tool for ArcGIS (ArcSWAT) to the Lumbee River watershed, also known as the Lumber River Watershed, in the coastal plain of North Carolina (USA) to better understand how streamflow may be impacted by predicted climate and land use change in the mid-21st century. The Lumbee River has cultural significance for Native American communities, including the 60,000-member Lumbee Tribe. Thus, we sought to understand effects of climate and land use change on the Lumbee River and on the surrounding, interdependent communities. We calibrated and validated ArcSWAT with historical climate and USGS streamflow data from the late 20th century. We then used mid-21st century climate and land use projections to simulate streamflows in ArcSWAT. Specifically, we used statistically downscaled climate forcing from general circulation models (GCMs) running the RCP8.5 scenario. We also used a land use projection from the USDA Forest Service's Southern Forest Futures Project. We simulated daily streamflow on the Lumbee River for the 2040-2060 period with uncertainty estimates derived from multiple GCM forcing and ensemble parameter sets. We identified shifts in streamflow by season and by flow frequency quantile for climate and land use change separately and in combination. We discuss implications for shifting flow regimes for the river, for its adjacent wetland and agricultural ecosystems, and for the related concerns of the Lumbee people.