1981 Volume 3 Issue 1 Pages 1-13
This paper consists of Part I and Part II. In part I, the measurements of the depth and the surface-and vertical-water temperature distributions which were carried out by means of the boat-borne infrared radiation thermometer, echo-sounding type fish detector and the thermistor thermometer, respectively, are described of crater lake Yugama, Volcano Kusatsu-Shirane, on the three days in the summer of 1978. The results show (1) the conical shape with 14.6 deg of the slope and 34.4±1.4m of the maximum depth, (2) 21.1°C of the mean surface water temperature with one high and one low regions which are considered in relation with upwelling of hot spring water and the slope of the lake bottom and (3) 19.6 t of the mean water body temperature with 20.8 to 23.4°C of the lake bottom temperature which suggests heat supply from the bottom to the overlaid water body. In Part II, to be published in not-so-distant issue, water and heat budgets of the lake will be discussed historically, based on the data presented here in connection with many morphometrical and thermometrical data in the previous papers.