Assessing Salinity Reduction by Environmental Restoration in the Seomjin River Estuary (South Korea): A Numerical Model Approach for Corbicula Habitat Conservation

This study modelled possible ways of reducing salinity in the Seomjin River estuary to improve habitats for corbicula, which are important components of the ecosystem (ecologically and commercially) in the Seomjin River. Additionally, we analyzed the salinity reduction effects of structural measures to sustain optimal salinity. To do this, salinity measurement facilities were installed at crucial habitat locations in the Seomjin River estuary. After ensuring the reliability of the model, numerical simulations were conducted. Salinity changes were analyzed for four major locations (Dugok, Shinbi, Mokdo, Hwamok) and simulated under various conditions, resulting in concentrations of 4.7 psu in Dugok, 16.0 psu in Shinbi, 19.2 psu in Mokdo, and 28.2 psu in Hwamok. Additionally, this study analyzed reduction effects by applying three reduction scenarios (riverbed restoration, submerged weir, and groyne) by simulating the numerical model. The reductions in salinity for the submerged weir (SWS-1 to 3) and groyne (GS-1 to 3) scenarios were minimal, below 1 psu, indicating a very limited reduction effect. In conclusion, the salinity concentration in the Seomjin River estuary is dominated by the neap tide, and the salinity intrusion distance is influenced more by the spring tide. The Songjeong discharge strongly impacts the spring tide, while the neap tide is less dominant due to salinity stratification. Among the salinity reduction scenarios, riverbed restoration has the most critical effect, but artificial reduction measures may pose challenges in terms of cost and practicality.