Evaluation of Temporal Contribution of Groundwater to a Small Lake through Analyses of Water Quantity and Quality

Groundwater can flow into or out of surface water and thus can greatly affect the quantity and quality of surface water. In this study, we conducted a water quantity and quality analysis for 11 months in 2018 and 2019 to evaluate the temporal contribution of groundwater to surface water at Osongji, a small lake located in Jeonju-si, Jeollabuk-do, Korea. Groundwater fluxes and groundwater and surface water levels were measured using seepage meters and a piezometer, respectively. On-site water quality parameters, cations, and anions for groundwater and surface water were analyzed. Hydrogen and oxygen isotopes for groundwater, surface water, and rainwater were also analyzed. Groundwater influx did not correlate directly to precipitation, suggesting that it may be delayed after rainwater infiltration. Aqueous chemistry indicated that the hydrogeochemical characteristics of surface water were substantially affected by groundwater. The isotopic composition of surface water changed over time, indicating a different contribution of groundwater in different seasons. This study shows that water quantity and quality data can be used in combination to evaluate temporal changes in the groundwater contribution to surface water.