Abstract
Soné-numa is a small and shallow basin located close to the east coast of Lake Biwa and is analogous to lagoons in it origin (Fig. 1). For further limnological works, the morphometric data were calculated on the basis of isobathic map (Fig. 2) made by the staff of the Laboratory of Analytical Chemistry, Nagoya University (Table 1). The basin is flat and rather steeper in the southern part than in the northern where it was dammed with a narrow sand-dune isolating it from Lake Biwa. This shallow lake of marshy appearance is in senescent stage of succession, leaving the open surface in the south-western part where its maximum depth of 2.2m. was sounded.
The only inlet of the lake is a small stream which flows into Soné-numa in its south-western end. This stream (Fig. 3) receives several brooks which are fed by springs derived from the seepage water of the Usogawa River, of which the middle course is quite devoid of water and which runs into Lake Biwa at the north of Soné-numa. In the second section of the present paper, the drainage area of this river is discussed to a certain extent in relation to Soné-numa.
