Streamflow Response to Climate and Landuse Changes in a Coastal Watershed in North Carolina

Abstract

It is essential to examine the sensitivity of hydrologic responses to climate and landuse change across different physiographic regions in order to formulate sound water management policies for local response to projected global change. This study used the U.S. Geological Survey's Precipitation Runoff Modeling System (PRMS) model to examine the potential impacts of climate and landuse changes on the monthly streamflow of the Trent River basin on the lower coastal plain of eastern North Carolina. The model was first calibrated and then validated using measured, historic, long-term daily streamflow. The model performed satisfactorily for simulating monthly streamflow, as indicated by an overall Nash-Sutcliffe simulation efficiency greater than 0.85. We examined the sensitivity of streamflow to changes in air temperature and precipitation. The simulations suggested that streamflow of individual years could change from -93% to 238%, depending on the two global circulation model (GCM) scenarios used (i.e., HadCMSul2 and CGC1). Streamflow of the Trent River will decrease with an increase in air temperature, and increase (or decrease) with an increase (or decrease) in precipitation. Streamflow was more sensitive to prescribed changes in precipitation than to air temperature for the study area, given its high and stable evapotranspiration rates in the humid climatic environment. Seven hypothetical landuse change scenarios representing forest conversion to crop lands and urban areas indicated that water yield could increase by 14% to 20%. The likely impacts of landuse changes may not be as high as those caused by predicted changes in climate, but moderate urbanization and extreme hydrologic events caused by climate change could pose significant water quantity and quality problems in the Trent River basin.