PREDICTION OF DESALINATION TIME OF SAEMANGEUM RESERVOIR

摘要

The Saemangeum reservoir is located on the western coast of the Republic of Korea and isconnected by a 33.9 km sea dyke. The Saemangeum watershed consists of the Mankyeongand Dongjin river watersheds, which have an immediate infl uence on the hydrodynamiccharacteristics of the Saemangeum reservoir. The objectives of this study are to simulate aseries of temporal and spatial distributions of water temperature and salinity to estimate therequired time for desalination of the Saemangeum reservoir and to suggest possible timingfor the fi rst agricultural water supply, considering the plan of the inner dike construction anddredging operations. To achieve this objective, EFDC, a hydrodynamic numerical model, iscalibrated using measured water temperature and salinity data. Considered conditions forestimating the required desalination period include: baseline without any salt input (SN1),percolated seawater amount through the sea dyke (SN2), leached salt amount from reclaimedareas (SN3), elution of salt from the benthic sediment layer (SN4), and the combined conditionsof aforementioned cases 2, 3, and 4 (SN5). The numerical simulation results show that thesalinity has a maximum value of 21 PSU during the spring season and the salinity graduallydecreases during the summer season due to the replacement of seawater by freshwater fromthe Mankyeong and Dongjin watersheds. The simulated period for desalination is 2.0-2.5years considering the conditions of percolated seawater and leached salt from the reclaimedareas, while the period of desalination is expected to take more than 5 years considering theconditions of salt elution from the benthic layer. Under the conditions that rural water can mostlybe supplied from the surface layer of the Saemangeum reservoir, it is expected to supplywater for agricultural use in 3 years after the desalination of the surface layer of the reservoir.Therefore, it may be concluded that both freshwater infl ow from upstream watersheds andsalt fl ux from the benthic sediment have the greatest infl uence on the desalination period,compared to lesser affecting conditions, such as percolated seawater through the sea dykeand leached salt from reclaimed areas.