For unconfined aquifers, the storage coefficient can be called specific yield, which is defined as a ratio of the volume of water which a rock or soil, after being saturated, will yield by gravity drainage to that of the rock or soil. Unconfined aquifers yield water to wells or other collection facilities because of drainage of pore space and air replacing water in the dewatered zone as the drop of the water table. Accordingly, if the height of the water table in an unconfined aquifer changes by an amount of 4h, the volume change in water storage per unit area, 4S, is given by, _??_ where Sy, is the specific yield. Because of this important relationship, many efforts have been made to determine the specific yield. Under natural conditions, the specific yield of an unconfined aquifer is often obtained by a pumping test, but this is an expensive procedure. Furthermore, a pumping test of short duration may not produce a full specific yield, because delayed release of pore water from a pumped unconfined aquifer usually occurs. Other methods to determine the specific yield are laboratory measurements on representative samples of the aquifer material, but such determinations are difficult. It is more reasonable to determine the specific yield by plotting the equilibrium volumetric water contents above the water table at the beginning and at the end of a certain drop of the water table. Estimates of the specfic yield can also be obtained by determining the difference between the porosity and the specific retention. In the present paper, the specific yield of Kan to Loam which is a volcanic ash layer covering diluvial uplands in Kanto district is evaluated from the relation between a certain drop of the water table and the volume change of water per unit area drained by a falling of the water table. In addition to this purpose, the author also investigated the relations between the soil water behavior taking place in Kanto Loam and the soil water characteristics of that soil. The study area is located at Imaichi dissected fan, Tochigi Prefecture (Fig. 1). Two test spots surrounded with a paddy field were selected as the representative fields of the fan. The study spots are covered with Kanto Loam (Fig. 2), which has physical properties as shown in Tables 1 and 2 and soil water characteristics as shown in Fig. 4. Water contents of the investigated soil were measured by the neutron method every 7 or 10 days during a ten-month period from April in 1973 to January in 1974. In each measurement, soil water contents were obtained at intervals of 0.2 m down to a depth of 7. 2 meters. Wet bulk densities were also measured by the gamma density meter at the same intervals of that neutron method. The three-phase distribution profiles in each month at the study spots are shown in Figs. 5 and 6. These figures offer some informations suggesting the behavior of the soil water taking place in Kanto Loam. Based on these data and the soil water characteristics of the investigated soil, the author calculated some significant parameters related to soil water characteristics of Ka.nto Loam, such as porosity, field capacity, specific retention and specific yield. These parameters are summarized in Table 3. The excess water retention above the field capacity in each depth seasona lly varied according to the water management in irrigation for the paddy field as shown in Figs. 7 and 8. As can be seen from Fig. 10, the specific yield calculated as the volume change of water by the drop of the water table showed some scatter but was essentially constant at a value of 16% for the spot 1 and 18% for the spot 2. Figure 11 shows the schematic relationship between profiles of the soil water content and the soil water characteristics for Kanto Loam, which was arranged from the data obtained through the present study. The results are summarized as follows.