Comparison of Time Series of Alluvial Groundwater Levels before and after Barrage Construction on the Lower Nakdong River

Abstract

Increasing the river cross-section by barrage construction causes rises in the average river water levels and discharge rates in the rainy season. The time series patterns for groundwater levels measured at 23 riverside monitoring wells along the lower Nakdong River are compared for two cases: before and after water-filling at the Changnyeong-Haman Barrage. Monthly average groundwater levels indicate a distinct increase in groundwater levels in the upstream riverside close to the barrage. River-water level management by barrage gate control in August, during the rainy season, resulted in a 0.1 m decrease in groundwater levels, while water-filling at the barrage in December caused a 1.3 m increase in groundwater levels. The results of hierarchical cluster analysis indicate that seven groundwater monitoring wells and river water levels were in the same group before barrage construction, but that this number increased to 14 after barrage construction. Principal component analysis revealed that the explanation power of two principal components corresponding to river fluctuation, PC1 and PC2, was approximately 82% before barrage construction but decreased to 45% after construction. This finding indicates that the effect of the river level component that contributes to change in groundwater level, decreases after barrage construction; consequently, other factors, including groundwater pumping, become more important. Continuous surveying and monitoring is essential for understanding change in the hydrological environment. Water policy that takes groundwater-surface water interaction into consideration should be established for riverside areas.

Enhanced monitoring of water quality variation in Nakdong River downstream using multivariate statistical techniques

“…As mentioned above, the backflow of saltwater was flowed into the river downstream during the summer season, which increased the EC concentration. However, the normal and low loading appeared from August 2012 due to low EC concentration because of the stabilization of the upstream river water level by the completed weirs [25]. The range of fluctuation of water level was decreased by the weirs after the barrage construction in the Nakdong River basin [26].…”

Characterizing the Impact of River Barrage Construction on Stream-Aquifer Interactions, Korea

“…The Quaternary alluvium has an average thickness of 1 to 33 m and is distributed predominantly along the sides of the Nakdong River and its tributaries. Kim et al [38] reported a sand layer with a thickness of 0.3 to 4 m, a gravel layer with a thickness of 1 to 10 m, and a weathered zone with a thickness of 1 to 3 m in and around the study area. On the basis of shallow hydrogeological profiles in the study area (Figure 2), the alluvial aquifer is composed of clay, sand, gravel, and weathered layers.…”

Spatio‐Temporal Variations in Stream–Aquifer Interactions Following Construction of Weirs in Korea

“…Thus, the influence of river‐level variations on the groundwater level decreased, and was largely controlled by precipitation. Principal component analysis also showed that the effect of the river‐level component that contributes to change in groundwater level decreases after weir construction; consequently, other factors, including groundwater pumping, become more important (Kim et al , ).…”