This study aims to estimate hydrogeological properties of riverside deposits in the middle part (the Gumi-Waegwan-Seongju area) of the Nakdong River basin. Hydraulic tests (pumping, slug, and infilitration tests) were conducted located near the Gumi Bridge, Waegwan Bridge and Seongju Bridge.
The...
This study aims to estimate hydrogeological properties of riverside deposits in the middle part (the Gumi-Waegwan-Seongju area) of the Nakdong River basin. Hydraulic tests (pumping, slug, and infilitration tests) were conducted located near the Gumi Bridge, Waegwan Bridge and Seongju Bridge.
The geology in the study area is composed of Precambrian Sobaeksan Complex, age-unknown granites, Triassic granites, Jurassic Daebo granites, sedimentary Sindong Group (Nakdong, Hasandong and Jinju Formations), volcanic Yucheon Group, and Cretaceous Bulguksa granites. Quaternary alluvium overlies all the above rocks by the unconformity. The fracture system in the study area is characterized by NE to NNE direction. This direction is similar to that of main and tributary Nakdong River system.
As the result of hydrogeological study, the geology of the fluvial deposits consists of medium sand layer, sandy gravel layer, weathered zone, and bedrock. The vertical thickness (28.6 m) is hickest in the Waegwan Bridge area. The horizontal extent (2km) of the riverside deposits is broader in the Seongju Bridge area than the other areas. This is because the hyporheic zone is more developed in the Waegwan and Seongju Bridge areas than the other areas. Transmissivity is higher as 1.62x10-3 m2/sec in the Waegwan Bridge area than the other areas. Unsaturated hydraulic conductivity ranges from 10.83 cm/hr to 366.04 cm/hr, reflecting the hydraulic property of sandy layer.
Groundwater level of the Seongju and Waegwan areas is stable with slight seasonal fluctuation. However, in the Gumi Bridge area, groundwater level is declining influenced by artificial pumping effect of the Gumi industrial complex. The relation between groundwater level and Nakdong River level is stronger in the concave bank than in the convex bank.
The ionic concentration is mostly higher in the convex bank than in the concave bank. Water type of the concave bank is Ca-HCO3 type and the convex bank is Na-HCO3 type. This is explained by high hydraulic energy acting on the concave bank, inducing strong hyporheic flow between the Nakdong River and the riverside deposits.
According to oxygen isotopes and total dissolved solids (TDS) methods, groundwater outflow between the Gumi Bridge and the Seongju Bridge is 4.56% in dry season and 10.46% in flood season. The groundwater outflow in the Waegwan-Seonju area is -7.36% of total river discharge, explaining the decrease of the Nakdong River discharge at the Waegwan Bridge. In addition, the hyporheic flow is stronger in the Waegwan Bridge area than the other areas.
This study aims to estimate hydrogeological properties of riverside deposits in the middle part (the Gumi-Waegwan-Seongju area) of the Nakdong River basin. Hydraulic tests (pumping, slug, and infilitration tests) were conducted located near the Gumi Bridge, Waegwan Bridge and Seongju Bridge.
The geology in the study area is composed of Precambrian Sobaeksan Complex, age-unknown granites, Triassic granites, Jurassic Daebo granites, sedimentary Sindong Group (Nakdong, Hasandong and Jinju Formations), volcanic Yucheon Group, and Cretaceous Bulguksa granites. Quaternary alluvium overlies all the above rocks by the unconformity. The fracture system in the study area is characterized by NE to NNE direction. This direction is similar to that of main and tributary Nakdong River system.
As the result of hydrogeological study, the geology of the fluvial deposits consists of medium sand layer, sandy gravel layer, weathered zone, and bedrock. The vertical thickness (28.6 m) is hickest in the Waegwan Bridge area. The horizontal extent (2km) of the riverside deposits is broader in the Seongju Bridge area than the other areas. This is because the hyporheic zone is more developed in the Waegwan and Seongju Bridge areas than the other areas. Transmissivity is higher as 1.62x10-3 m2/sec in the Waegwan Bridge area than the other areas. Unsaturated hydraulic conductivity ranges from 10.83 cm/hr to 366.04 cm/hr, reflecting the hydraulic property of sandy layer.
Groundwater level of the Seongju and Waegwan areas is stable with slight seasonal fluctuation. However, in the Gumi Bridge area, groundwater level is declining influenced by artificial pumping effect of the Gumi industrial complex. The relation between groundwater level and Nakdong River level is stronger in the concave bank than in the convex bank.
The ionic concentration is mostly higher in the convex bank than in the concave bank. Water type of the concave bank is Ca-HCO3 type and the convex bank is Na-HCO3 type. This is explained by high hydraulic energy acting on the concave bank, inducing strong hyporheic flow between the Nakdong River and the riverside deposits.
According to oxygen isotopes and total dissolved solids (TDS) methods, groundwater outflow between the Gumi Bridge and the Seongju Bridge is 4.56% in dry season and 10.46% in flood season. The groundwater outflow in the Waegwan-Seonju area is -7.36% of total river discharge, explaining the decrease of the Nakdong River discharge at the Waegwan Bridge. In addition, the hyporheic flow is stronger in the Waegwan Bridge area than the other areas.
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