大橋川における高塩分水塊の遡上現象

Appearance of a high-salinity water mass that frequently intrudes into the Ohashi-River from the Lake Nakaumi and causes oxygen-deficient water mass in Lake Shinji in San'in District, western Japan, has been studied with special reference to the variations in water levels as well as wind patterns in Lake Nakaumi. Although no seasonal fluctuations in the high -salinity water mass index(HSI) were found, correlations seemed to exist between the monthly HSI and the water level differences as well as discharge of the Hii River. In a shorter time-scale, it was probable that the level of HSI increased when water level differences were large. The average velocity of the high-salinity water mass was estimated to be 0.44 m/s. Large HSI occurred more frequently during westerly winds than easterly ones, suggesting thereby that some of the HSI were associated with the rise of wind-induced halocline. Extensive HSI was likely to occur when the difference of water level was large and westerly winds prevailed.