Evaluation of the Impact of Meteorological Factors on the Stratification of Structure in Lake Biwa, Japan

Abstract

Hypoxia in Lake Biwa, Japan remains a serious water environmental problem. One of the causes of hypoxia in the lake is the formation of a thermocline, which is largely affected by meteorological factors, such as (1) air temperature, (2) wind speed, and (3) precipitation. However, the effects of these three meteorological factors on the formation of the thermocline have not been clarified quantitatively. In this study, applying a three-dimensional hydrodynamic model to Lake Biwa, the effects of each of the three meteorological elements on the formation of the thermocline was quantitatively analyzed to clarify the governing factors of meteorological conditions in the formation of anoxic oxygen. Sensitivity analysis of the stratification structure in Lake Biwa was performed by changing the three meteorological factors of (1) air temperature, (2) wind speed, and (3) precipitation. As a result, the change in wind speed gives the greatest effect on the stratification structure, the change in air temperature makes the difference in the stratification structure from the surface layer to the vicinity of the thermocline, and the change in precipitation affects it less than the others.