FUNDAMENTAL STUDY ON DISSOLVED OXYGEN SUPPLY INTO DEEP LAYERS IN LAKE BIWA

Abstract

In this paper, using data from consecutive observations of Lake Biwa water quality and existing long-term weather observation data, the authors clarified the mechanism in which water temperature and dissolved oxygen (DO) concentration in deep layers of Lake Biwa change during the period from autumn to winter, i.e. from the stratification collapse period to the circulation period. The relationship between the DO recovery of deep layers and the air temperature in the circulation period was also studied. The amount of the DO supply to the deep layers by circulation was then calculated as a trial, and compared to the results of investigations related to water temperature and water quality in Lake Biwa.
As a result, it was clarified using measured data that the oxygen supply by lake water circulation through the surface of the lake was predominant in the mechanism of DO supply to the deep layers in Lake Biwa than the DO inflow caused by melted snow. It was also pointed out that the coldness of winter which hits during the circulation period was essential in the DO recovery of deep layers.