Behavior and relationship of land and lake originated suspended substance in a lake

Research Project

Project/Area Number	10640422
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	Meteorology/Physical oceanography/Hydrology
Research Institution	Shiga University
Principal Investigator	ENDOH Shuichi Shiga Univ., Faculty of Education, Prof., 教育学部, 教授 (30111884)
Project Period (FY)	1998 – 1999
Project Status	Completed (Fiscal Year 1999)
Budget Amount *help	¥3,000,000 (Direct Cost: ¥3,000,000) Fiscal Year 1999: ¥1,200,000 (Direct Cost: ¥1,200,000) Fiscal Year 1998: ¥1,800,000 (Direct Cost: ¥1,800,000)
Keywords	Suspended substance / Lake Biwa / River water / Phytoplankton / Water temperature / Turbidity / 湖底高濁度層 / 湖流
Research Abstract	Suspended substance in a lake is divided into two types, that is a land-originated substance and lake-originated substance. This study focuses on behavior of these substance and also on the relationship between these two. Three dimensional observations of water temperature, electric conductivity, turbidity and chlorophyll a have been carried in Lake Biwa every month from May 1998 to February 2000. At some stations, we sampled water and analyzed SS concentration, ignition loss and chemical element. Two thermistor chain have been set both at Yasu River and Lake Biwa to be recorded water temperature continuously. From these observations, seasonal change of river inflow with substance are clarified. In spring season the river water inflows over the surface layer of the lake. During summer and fall seasons, river water intrudes into the thermocline depth. In winter, river water sinks at the river mouth and is transported offshore by the density current. In the spring season and dry season, the lake-originated substance such as phytoplankton is much important in the SS concentration. After heavy rainfall, the land-originated substance is increased and sink with the lake-originated substance. By comparisons of water temperature between the lake water and river water, the water budget was estimated with a high resolution.