[A-CG42] Water and sediment dynamics from land to coastal zones

[ACG42-05] Estimation of coastal freshwater discharge using surface salinity of Nanao Bay

*Shiho Kobayashi¹, Satoshi Nakada², Kei Senbokuya³, Jun-ichi Okuno ³ (1.Kyoto University, 2.National Institute for Environmental Studies, 3.Ishikawa Prefecture Fisheries Research Center)

Keywords:freshwater discharge, catchment area, surface salinity, coastal sea model, runoff coefficients

Extremely heavy rainfall impacts on marine environment; it causes the significant decrease of surface salinity and intensifies density stratification in coastal seas, and might result in depletion of dissolved oxygen in the lower layer. The study area, Nanao Bay is a semi-enclosed bay in Noto Peninsula faced on Japan Sea. There is no public data of river discharge flowing into the bay, which is important to investigate the impacts of heavy rainfall on the marine environment. On the other hand, salinity in the bay has been monthly measured by Ishikawa Prefecture Fisheries Research Center and daily rainfall is publicized by Japan Meteorological Agency. This study employed a numerical model, FVCOM (Chen et al., 2003) for estimating the decrease of salinity in the surface layer of the bay associated with freshwater discharge which was estimated using the catchment area, rainfall data and runoff coefficients. The Green’s functions method was then applied for inverse estimation of the runoff coefficients using the simulated and the observed salinity in the bay.