Abstract
The writer carried out some investigations in order to estimate the amount of groundwater flow in Koromo Basin, the Yahagi River valley. He surveyed the geology of the basin by means of the electric resistivity method, using an apparatus of the Electro-Technical Laboratory type (Fig. 1). Koromo Basin is drained by Yahagi Valley and is filled up by granite, Tertiary formations and Diluvial (? ) and Alluvial deposits. Alluvial sand and gravel layers are of great importance in the study of the groundwater hydrology, for they now constitute the source of most productive and intensively used groundwaterr supply.
About 110 wells were examined and a groundwaterr contour map was obtained (Fig. 2). From this map, direction and gradient of the groundwater flow were procured. He evaluated permeability coefficient k by Tiem's E method and discussed its accuracy by other methods. Using these data above mentioned, he calculated groundwater amount through a valley section and obt_??_ined 2.63 m3/sec as the total groundwater discharge through a valley section (Fig. 3. 4. 5. Table 1. 2. 3).
This amount answers to a relative discharge of 0.236m3/sec/100km2. It is not without interest that this sum is almost equal to the relative ordinary discharge of the Yahagi River:-i. e. 0.270m3/sec/100km2.
