STREAM WATER - GROUNDWATER INTERACTION CHANGES IN LOWER NAKDONG RIVER BASIN BY USING THE TIME SERIES ANALYSIS AND GROUNDWATER QUALITY

摘要

Total of sixteen river dams has been constructed in four major rivers in South Korea(eight at the Nakdong River, three each at the Han River and Geum River, and two at theYeongsan River) for the purpose of fl ood control and effective water resource vis-a-vis climatechange. However, the river dam construction induced groundwater level rise and streamwater-groundwater interaction at the upstream regions of the river dams. In this study, weexamined stream water-groundwater interaction properties by using the time series analysisof groundwater level and river water level with groundwater quality at the Changreong-Hamanriver dam in lower Nakdong River. Total of 34 manually monitored wells and 5 automaticallymonitored wells in the riparian zone of the Gwangryeo Stream and Iryeong Stream tributariesof the Nakdong River were observed during Mayl 2011–September 2013 with river level(Ducknam observatory station) and rainfall (Jindong rainfall station). As a result of this study,the groundwater level was found to rise by an average of 1.62 m for the observed period. Thecross-correlation function of groundwater level and Nakdong river level has changed from0.04-0.68 (before river dam) to 0.05-0.71(after river dam) and response time ranged 3-229hours(before river dam) to 1-251 hours(after river dam). Also, groundwater quality displayeda lower Ca2+, HCO3-, and CO32- concentration and higher NO3- concentration near theNakdong River after river dam construction. These are indicating a greater interaction betweengroundwater and river water due to the river dam.