Hydrogeological and hydrochemical characteristics of alluvial groundwater and river water in the Nakdong River basin

Category Hydrogeology
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Hamm, Se-Yeong۱; Cheong, Jae-Yeol۱; Lee, Jeong-Hwan۱; Kim, Hyoung-Soo۲; Lee, Sang Il۳
Holding Date 03 September 2008

In Korea, the dominant portion of municipal water comes from regional water supply system which uses dam water and river water. The other less important portion is from provincial water supply and village water supply systems. However, Korea has been confronted with the degradation of drinking water quality due to worsening of source water quality because of artificial pollution. In this situation that downstream areas were encountered with quality problem more crucially than upstream areas, riverbank filtration has been attracted by central and provincial governments as a substitute for water sources. In relation to riverbank filtration, this study aimed to reveal hydrogeological and hydrochemical characters of alluvial groundwater and stream water in seven areas of the middle and low Nakdong River basins. In the middle section of the river, hydraulic conductivity (K) of alluviums ranges from the order of 10-6 to 10-5 m/s. By contrast, in the lower section of the river, K of alluviums ranges from the order of 10-6 to 10-5 m/s. Electrical conductivity of the river is distributed between 209 to 262 mS/cm in the middle section while it is in 460 and 608 mS/cm in the lower section, indicating stronger impact of pollution toward downstream. Electrical conductivity of alluvial groundwater turned out between 247 and 419 mS/cm in the middle portion whereas it was in the range of 505 and 756 mS/cm in the lower section of the Nakdong River basin. Hydrogen and oxygen isotope analyses of the river water resulted in -58.5 and -61.4¢ of ¥نD, and -7.83 and -8.42 of ¥ن18O in the middle section. According to hydrogen and oxygen isotope analyses of alluvial groundwater, the values of ¥نD ranged from -53.6 to -65.0, and ¥ن18O ranged from -7.41 and -8.95in the middle section. On the other hand, ¥نD of river water ranged from -51.7 and -64.8and ¥ن18O of river water from -7.93 and -9.01 in the lower section; ¥نD and ¥ن18O of riverbank filtered water were between -56.6 and -7.88respectively, in the lower section. In the middle and lower basins, the river water and alluvial groundwater mostly belong to Ca-HCO3 type, regardless seasons. Yet, the river water shows more diverse water types than the alluvial groundwater. This indicates that the river water is more vulnerable to man-made contamination than the alluvial groundwater, and also directly affected by precipitation. Besides, going downstream, chemical properties of the river and the alluvial groundwater are degraded due to anthropogenic pollution. The authors wish to acknowledge the financial support of the Sustainable Water Resources Research Center under the program of the 21st Century Frontier R&D Program (project no: 3-4-3).