| The results of recent current measurements in Lake Biwa are described.
Two methods have been applied to measure the water movements. One is the
continuous current measurements by using current meters, and the other
is the tracking of drifters by using a radar. The gyres in the northern
basin of Lake Biwa are quite stable in the season of thermal stratification.
The locations of the gyres are quite different from those of the old study.
A vertical circulation consisting of horizontal convergence in the surface
layer is found in the cyclonic gyre. This vertical circulation should play
an important role in the sedimentation process. Internal waves have a great
influence on the current field of the offshore zone as well as the coastal
zone. Water movements in the deep layer and the bottom layer are strongly
controlled by the internal waves. Under the influence of a strong wind
blowing perpendicular to the shore line, coastal bottom water is often
transported offshore. The front of turbidity exists in the area about 3
km south of Biwako Ohashi Bridge both in the summer and winter. After two
or three days from the cold wave, the colder water in the eastern part
of the southern basin flows continuously into the bottom layer of the northern
basin for several days. |