Consideration on Changes of Density Stratification in Saemangeum Reservoir

Oh, Chul‐Woong; Choi, Jung-Hoon

doi:10.7846/jkosmee.2015.18.2.81

Cited by 10 publications

(9 citation statements)

References 8 publications

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“…From April 2006 to December 2010, the sluice gates on the southern parts of the seawall remained open, allowing unrestricted interaction between freshwater and seawater. However, from January 2011 to August 2014, the sluice gates were opened selectively twice daily (daytime and nighttime) for one hour to manage the water levels within the inner area (Oh and Choi, 2015). The sluice gates were opened once daily for less than one hour between Sep. 2014 and Nov. 2020.…”

Section: Study Areamentioning

confidence: 99%

“…The Saemangeum seawall sluice gates irregularly control freshwater and seawater exchange, contributing to increased environmental stress (Lee et al, 2009;Kim et al, 2020). In summer, when freshwater inflow is high owing to increased precipitation (Park and Sin, 2022), the influence of low salinity on freshwater becomes more pronounced, leading to strong stratification of internal waters (Kim et al, 2006;Oh and Choi, 2015). The outer region has an average salinity above 28 psu in the outer region, whereas the inner region has an average salinity below 25 psu.…”

Section: Introductionmentioning

confidence: 99%

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Coastal environmental changes after the Saemangeum seawall construction

Baek,

Guerreiro,

Kim

et al. 2024

Front. Mar. Sci.

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The coastal environment in the Saemangeum area has experienced persistent physical stresses owing to the irregular operation of the sluice gates and related artificial disturbances since seawall construction, which has led to restricted freshwater-seawater circulation. To understand the impacts of stress, we performed long-term (1999-2022, 24 years) in situ measurements of relevant biotic and abiotic parameters and employed the random forest (RF) technique to determine the phytoplankton community response to environmental disturbance. Specifically, we estimated chlorophyll-a (Chl-a) concentrations using an RF model based on various environmental factors such as sea surface temperature (SST), sea surface salinity (SSS), dissolved oxygen saturation (DO), dissolved inorganic nitrogen (DIN), and dissolved inorganic phosphorus (DIP) as input variables. From the RF analysis, each environmental factor contributed to variation in Chl-a concentration as follows: SSS (42.91%), SST (17.88%), DIP (14.38%), DIN (13.36%), and DO (11.48%). In addition, we performed sensitivity experiments by altering the salinity, which was revealed to be the most influential environmental parameter. As a result, Chl-a concentration increased by approximately 1.79 times in lower salinity conditions (from 7 to 27 psu) compared to the normal salinity conditions prior to the seawall construction (from 12 to 32 psu) in both areas, including the inside and outside the seawall. More importantly, lower salinity conditions stimulated dinoflagellate blooms, that is, red tides, implying that restricted freshwater-seawater circulation could worsen coastal ecosystems. Thus, this study contributes to understanding the impacts of environmental changes caused by sluice gate manipulation on marine ecosystems, such as phytoplankton community dynamics. Moreover, this study recommends an ecologically suitable operation scheme for Saemangeum sluice gates to ensure a healthy coastal ecosystem.

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Section: Study Areamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Coastal environmental changes after the Saemangeum seawall construction

Baek,

Guerreiro,

Kim

et al. 2024

Front. Mar. Sci.

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“…The seawall project was initiated in year 1991 and complete in year 2006 as the largest man-made dike (Beigel & Christou, 2010). This project has caused public concerns, controversial environmental issue as well as intense political turbulence in the recent history (Koh et al, 2010). With these constructed first generation of CRs, it was concluded that first-generation CR has to improve in order achieve environmental sustainability.…”

Section: First Generation Of Crmentioning

confidence: 99%

Hydrodynamic modelling and shape optimisation of second-generation coastal reservoirs in consideration of algal bloom occurrence

Wong

Teo²

2023

Environ Dev Sustain

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Algal bloom has been a persistent problem for both fresh and marine water, with no exception for a coastal reservoir (CR). Among the algal bloom mitigations for a CR, shape optimisation to reduce algal bloom occurrence has been frequently mentioned. However, there was no literature found on the actual shape optimisation study or process for CR. Thus, this research was done to bridge this gap, particularly for the second-generation CR. Hydrodynamic model of MIKE 21 has been used, with secondary data obtained from published papers and Google Earth. The secondary data of critical velocity corresponding to algal growth were only available for cyanobacteria, chlorella, filamentous algae and phytoplankton. Hence, only these algae species were considered in the algal mapping. All models were simulated for eight idealised cases of second-generation CR at the Yangtze Estuary. These different geometric shapes were analysed and compared, considering several factors including the average velocity in the reservoir, presence of stagnant water, percentage of occurrence for each algae species and so on. From the results, the reservoir model with the shape of “shorter piano key” ranked the highest among all the shapes in terms of proneness to algal bloom, based on the flow velocity within the reservoir. From the findings, further shape optimisation was done on second-generation CRs. From shape optimisation process, the optimised shape of the “little dinosaur” and “little pencil” showed excellent reduction in algal blooming. However, “little dinosaur” was preferred as its location for algal bloom is small and controllable due to the presence of “piano key” structure. Lastly, all the findings were applied to an existing CR at Qingcaosha to see if shape optimisation based on the analysis can reduce areas prone to algal blooming. The optimised model of Qingcaosha showed great reduction on area prone to algal blooming compared to its original shape but the addition of “piano key” structure did not have significant impact on the reduction of algal bloom occurrence since the shape of Qingcaosha is highly dependent on its natural topography. From the study, it was concluded that shape optimisation for topographic-dependent CR should be done on case-by-case basis, following the flow direction in the reservoir. As for second-generation CR without topographical constraints, the shape optimisation can be done by placing inlet perpendicular to the flow direction, minimising corners, implementing piano-key-like structure, optimising shape based on flow direction and refer “little dinosaur” or “little pencil” for the overall shape optimisation design.

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“…This Saemangeum artificial lake receives terrigenous effluents mainly from the Mangyeong and Dongjin Rivers, and their annual freshwater discharges are 1100 × 10 6 and 700 × 10 6 m 3 /year, respectively [19]. The water level of the Saemangeum artificial lake is maintained at 1.6 m below sea level [23], and thus, water exchange between the coastal waters and the artificial lake is restricted, occurring only episodically when it is necessary to control the water level and quality, such as during heavy precipitation in the watershed or during drought. Before construction, the tidal range in the study area was up to 6 m; after construction, it is less than 1 m, even when the sluice gates are fully open [24,25].…”

Section: Site Descriptionmentioning

confidence: 99%

Assessment of Water Quality in a Coastal Region of Sea Dike Construction in Korea and the Impact of Low Dissolved Oxygen Concentrations on pH Changes

Lee

et al. 2023

JMSE

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To investigate the factors affecting water quality in coastal regions with sea dike constructions, surface water outside a sea dike was monitored for six years from 2015 to 2020 in the Saemangeum region of Korea. Statistical analyses of the six years of high-frequency measurements revealed that the water quality in this system was predominantly governed by natural processes followed by pollutant inputs as the secondary influencing factor. Severe dissolved oxygen (DO) depletion was observed in the surface waters during warm periods, probably owing to the advection of DO-depleted water from elsewhere to the surface layer. Based on the apparent oxygen utilization (AOU)–pH relationship (r = 0.52, n = 1837), the maximum AOU (180 µM) led to a pH decrease from 8.04 to 7.50, which was considerably lower than the estimated value of 7.72. This extra pH drop was probably due to a reduction in the buffering capacity associated with increased CO2 in the water column originating from the atmosphere and in situ production, as well as local water column redox reactions associated with benthic inputs of reduced chemical species. Overall, persistent DO depletion with ongoing eutrophication/hypoxia could accelerate ocean acidification in Korean coastal waters, which could be more acute in coastal regions with artificial coastal constructions.

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Consideration on Changes of Density Stratification in Saemangeum Reservoir

Cited by 10 publications

References 8 publications

Coastal environmental changes after the Saemangeum seawall construction

Coastal environmental changes after the Saemangeum seawall construction

Hydrodynamic modelling and shape optimisation of second-generation coastal reservoirs in consideration of algal bloom occurrence

Assessment of Water Quality in a Coastal Region of Sea Dike Construction in Korea and the Impact of Low Dissolved Oxygen Concentrations on pH Changes

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