| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1997: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1996: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
In order to clarify the behavior and circulation of the suspended materials in the bottom layr and the thermocline, the following observations have been carried out.
1)Routine Observation : Vertical profiles of water temperature, electric conductivity, turbidity and Chlorophyll a were measured in the south area of the north basin of Lake Biwa once a month. At the same time, the Secci disk depth, pH,and wind were observed. Water sampling were also made to determine the concentrations of SS,the ignition loss and chemical element in SS.
2)Continuous recording of current, water temperature and turbidity : Automated current meters and turbidity meters were set to get the continuous records of current and turbidity. Thermometers were set both in the river and the lake to determine the dispersion of the river water into the lake.
3)Sediment trap observation : Five sediment traps were set at three points to measure the SS concentration, ignition loss, chemical elements and particle size.
On the basis of these observations, we obtained the following results ;
1)The river water flows into the surface layr of the lake in spring, but flows into the bottom layr and then intrudes into the thermocline depth in summer and autumn. In winter, the river water flows into the bottom layr and is strongly mixed in vertical by the wind and surface cooling.
2)The benthic nepheloid layr is maintained throughout the seasons of thermal stratification. The turbidity in the benthic nepheloid layr is maintained by organic matter such as phytoplankton under decomposition, but is much affected by the inorganic matter from rivers after heavy rainfall.
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