Effects of Short Time Variation in the River Discharge on the Salt Wedge Intrusion in the Yura Estuary, a Micro Tidal Estuary, Japan

Tatsuhiro Funahashi, Akihide Kasai, Masahiro Ueno, Yoh Yamashita

Field Science Education and Research Center, Kyoto University, Maizuru, Japan.
Graduate School of Agriculture, Kyoto University, Kyoto, Japan.

DOI: 10.4236/jwarp.2013.53A035                

Abstract

A numerical model was developed to investigate salinity distribution in the Yura Estuary, a micro tidal estuary in Japan. The model results show that the salinity distribution as represented by salt wedge intrusion agreed well with field observations. In addition to the seasonal variation, the salt wedge responds over short time scales according to the flood events. The retreat of the salt wedge is dependent on the scale of the river discharge; the salt wedge moved back and disappeared from the estuary when over250 m³·s^-1 of fresh water was discharged from the estuary and it takes ~11 days for salt wedge to recover from the fresh water discharge event. The Yura Estuary has on average three floods during summer, this coincides with when phytoplankton is most productive in the river and indicates that the short temporal variations in the river discharge has important effects not only on the hydrodynamics, but also on the ecosystem in the estuary.

Keywords

Micro Tidal Estuary; River Discharge; Salt Wedge Intrusion; Short Time Variation

Conflicts of Interest

The authors declare no conflicts of interest.

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