Abstract
The extreme variation in the amount of annual precipitation and rainfall during single events is typical of the East Asian monsoon climate and may greatly influence the characteristics of the suspended sediment load. The turbidity in Lake Imha which is the eighth largest multipurpose dam in Korea has been the cause of major water quality problems for use as drinking water. The turbidity rose to 882 NTU, and it remained over 30 NTU continuously for 170 days during 2002, as the result of significant amounts of soil erosion from the watershed during the Asian monsoon typhoon. In this study, characteristics of suspended sediment loadings under the Asian summer monsoon climate was investigated by comparing the variation of yearly suspended sediment loads and the ratio of maximum suspended sediment loads in a single event to yearly suspended sediment load from Lake Imha watershed using the Hydrologic Simulation Program-FORTRAN (HSPF). The model calibration is performed according to the 2009–2010 events, and simulation results characterized suspended sediment loadings under the Asian summer monsoon climate for 2001–2010. Water sampling and flow rate measurements were performed every 4–6 h, and calibration was performed using hourly simulated sediment loads. The calibration results demonstrated good agreement with the observed data. The characteristics of suspended sediment loadings under the Asian summer monsoon climate are a high variance of the yearly suspended sediment load and a significant of amount of suspended sediment load during a single event influenced by the typhoon intensity. The maximum yearly suspended sediment load was 10 times higher than the minimum yearly value. About half of the yearly suspended sediment load was loaded with a single event under the Asian summer monsoon climate and the ratio of suspended sediment loads by a single event to total yearly loads ranged from 29% to 90%. Structural best management practices (BMPs) to trap suspended sediment in stormwater such as stormwater ponds or wetlands rely on much more storage volume or area and non-structural BMPs to minimize soil erosion by source control such as mulching or revegetation in disturbed areas, which are important BMPs, especially in the Asian summer monsoon region.
Highlights
The rainfall under an Asian summer monsoon climate is strongly concentrated in summer in Korea
Soil erosion can be a major factor in water quality problems caused by the Asian summer monsoon typhoon in Korea [1]
Hydrologic Simulation Program-FORTRAN (HSPF) is available from the U.S Environmental Protection Agency (U.S EPA)
Summary
The rainfall under an Asian summer monsoon climate is strongly concentrated in summer in Korea. Significant amounts of nonpoint source pollution are generated which flow into water bodies. Soil erosion can be a major factor in water quality problems caused by the Asian summer monsoon typhoon in Korea [1]. Pollution tightly attached to sediment can cause water quality problems. Crabill et al [3] identified sediment with high fecal coliform counts, averaging 2200 times higher than those of the water column, which causes a deterioration in water quality during the summer season in Oak Creek, Arizona, USA. The major source of phosphorus, which causes eutrophication in lakes and reservoirs, was found to be soil erosion in the Hii River basin, Japan [4]
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