Determining Groundwater Drought Relative to the Opening of a River Barrage in Korea

Abstract

Groundwater droughts are one of the natural disasters that raise serious water issues for humans, and are increasing in frequency due to global climate change. In order to identify groundwater droughts, we recorded groundwater level fluctuations upstream at Changnyeong-Haman River barrage from May 2012 to October 2020, based on the groundwater level characteristics and Nakdong River stages. Next, we grouped groundwater levels by K-means clustering, converted groundwater levels to kernel density estimation (KDE), and calculated a standardized groundwater level index (SGLI). Finally, we judged groundwater drought by using the SGLI values corresponding to the opening and closing of the barrage. In the study area, the SGLI criteria for discriminating groundwater drought were −0.674 (caution), −1.282 (severe), and −1.645 (very severe), respectively, corresponding to the 25th, 10th, and 5th percentiles. Based on the SGLI values, groundwater levels on the monitoring wells mostly lie below the 25th percentile during the five opening periods of the barrage. According to cross-correlation analysis, the groundwater level sensitively reacted with the river stage, which influenced groundwater drought. As a result, the SGLI along with the river stages was verified as an efficient tool for evaluating groundwater drought as well as for appropriately operating the barrage.