Numerical Modeling for Region of Freshwater Influence by Han River Discharge in the Yeomha Channel, Gyeonggi Bay

Abstract

This study estimates the region of freshwater influence (ROFI) by Han River discharge in the Yeomha channel, Gyeonggi Bay. A 3-D numerical model, which is validated for reproducibility of variation in current velocity and salinity, is applied in Gyeonggi Bay. Distance of freshwater influence (DOFI) is defined as the distance from the entrance of Yeomha channel to the point where surface salinity is 28 psu. Model scenarios were constructed by dividing the Han River discharge into 10 categories (200~10,000 m3/s). The relation equation between freshwater discharge and DOFI was calculated based on performing a non-linear regression analysis. ROFI in Yeomha channel expands from the southern sea area of Ganghwa-do to the northern sea area of Yeongheung- do as the intensity of Han River discharge increases. The discharge and DOFI are a proportional relationship, and the increase rate of DOFI gradually decreases as discharge increases. Based on the relation equation calculated in this study, DOFI in the Yeomha channel can be estimated through the monthly mean Han River discharge. Accordingly, it will be possible to respond and predict problems related to damage to water quality and ecology due to rapid freshwater runoff.

Effect of Freshwater Discharge on the Water Quality in Cheonsu Bay, West Coast of Korea

“…However, the limiting nutrient changed to phosphorus (DIN/DIP of 16 or more) during freshwater discharge. This is consistent with previous studies showing that phosphorus acts as a limiting nutrient when fresh water is discharged from Cheonsu Bay (Lee, Choi, and Song, 2019).…”

“…In general, phosphorus in freshwater ecosystems and nitrogen in seawater ecosystems act as limiting nutrients (Hecky and Kilham, 1988;Kim et al, 2022). The N/P ratio varies depending on the type and amount of nutrients introduced from the water system where the discharge exists, such as estuaries, leading to changes in the limiting nutrient (Lee, Choi, and Song, 2019;Yoon, 2012). In this study, it was confirmed that the limiting nutrient before freshwater discharge was nitrogen, which has with a DIN/DIP of 16 or less.…”

Evaluation of Spatiotemporal Variations in Water Quality Along the Chungnam Province Coast and Inner Estuary (West Coast of Korea)

“…In fact, hypoxia occurs in the bottom water inside Cheonsu Bay during summer (Jung et al, 2015;Lee, Kim, and Lee, 2016). Owing to hypoxia, marine organisms are directly and adversely affected and may occasionally result in their death (Lee, Choi, and Song, 2019;Lee et al, 2014). Numerous studies have been conducted in Cheonsu Bay, focusing on the changes in marine environments before and after dike construction, including studies on the distribution and geochemical sediment characteristics in Cheonsu Bay (Kim and Jang, 2014;Yoon, Lee and Yoon, 2021).…”