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Title: Temporal variations in baseflow for the Little River Experimental Watershed in South Georgia, USA

Author
item Bosch, David
item Arnold, Jeffrey
item ALLEN, PETER - Baylor University
item LIM, KYOUNG-JAE - Kangwon National University
item SHIK, YOUN - Kongiu National University

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2017
Publication Date: 3/17/2017
Citation: Bosch, D.D., Arnold, J.G., Allen, P., Lim, K., Shik, Y. 2017. Temporal variations in baseflow for the Little River Experimental Watershed in South Georgia, USA. Journal of Hydrology. 10:110-121. https://doi.org/10.1016/j.ejrh.2017.02.002.
DOI: https://doi.org/10.1016/j.ejrh.2017.02.002

Interpretive Summary: A detailed characterization of the portion of streamflow attributed to direct surface runoff and that attributed to water flow which travels through the soil is critical to understanding hydrologic and water quality processes at the watershed scale. Streamflow data collected by the Southeast Watershed Research Lab from the Little River Experimental Watershed in the Southern Coastal Plain were analyzed to separate these surface and subsurface (baseflow) components. Baseflow for this watershed was found to produce 53% of annual streamflow, 14% less than prior published results. Baseflow was the largest during the months from December through May (55-57%) and the least during the months from June through November (43-46%). Annual BFI index was found to decrease with increasing annual precipitation. These provide important baseline values for hydrograph separation in Coastal Plain Watersheds.

Technical Abstract: Water flow across the soil surface and in streams is the driving force of sediment, nutrient, and pesticide movement. Separation of streamflow hydrographs into rapid surface runoff and baseflow, the portion of streamflow coming from vadose zone and groundwater sources, can vastly improve our understanding of watershed processes. Data collected at the Little River Experimental Watershed (LREW) in the Southern Coastal Plain Major Land Resource Area of the U.S.A. (N31'26’13”, W83'35’17”) from 1972 to 2015 were used for hydrograph separation. Greater precipitation and lower evapotranspiration rates during the winter and spring months in the region create higher soil-moisture and greater aquifer recharge, increasing surface runoff responses and groundwater contributions to streamflow. Baseflow makes up a large fraction of the streamflow during the winter and spring periods. Thus, baseflow is extremely important to sustaining streamflow throughout the SCP. Increasing demands on groundwater, changes in land-use, and changes in precipitation patterns due to climate change are all expected to impact baseflow conditions and streamflow volume. The two parameter Eckhardt digital filter method used for separation of high and low frequency signals was used for baseflow separation. The method requires estimation of two fitting parameters, BFImax and alpha (a). The baseflow index (BFI) is the ratio of baseflow volume to total streamflow volume. BFImax was set at 0.80 and a at 0.98. Baseflow was found to produce 53% of annual streamflow, 14% less than prior published results. Baseflow was the largest during the months from December through May (55-57%) and the least during the months from June through November (43-46%). Annual BFI index was found to decrease with increasing annual precipitation.