In studying the hydrologic balance such area that permeable materials like sand, gravel or ash and weakly welded pumice flow of the Quarternary, cover impermeable bedrocks, it is extremely important to check whether the specified geological conditions, which will cause the watershed leakage from one river basin to another exist or not.
Generally speaking, the underground divide does not necessarily coincide with the topographic divide in such area due to the relief of bedrocks underlain by permeable materials. Consequently, a part of groundwater which infiltrated in the permeable materials flow across the topographic divide along the surface of the bedrocks.
This report describes a result of investigation on the hydrologic balance in the Kimotsuki River basin (about 450km²) by taking into consideration of all possible items relating to the hydrologic balance, especially to the watershed leakage.
Dr. K. Ogasawara investigated the hydrologic balance of this river basin based on the statistics for three years, 1967 to 1969, and confirmed that the average amount of annual flow (2350mm) is in excess of the average amount of the estimated rainfall (2107mm). However, the amount of loss by spontaneous evaportaion is assumed to be approximately 300mm (i. e. actual annual rainfall of this area comes to 2407mm). This is the reason why Dr. K. Ogasawara suggested the possibility of the watershed leakage of groundwater from another river basin area into the Kimotsuki River basin.
A field investigation by the authors and various published geological data showed the following properties in this area and its vicinity.
1) In the Kimotsuki River basin and its vicinity, pumice flows (20 to 50m in thickness, and probably pleistocene in age) which is commonly known in Japan as “Shirasu” distribute unconformably covering the Nichinan formation which is mainly composed of sandstones and shales in alternation. No doubt, the “Shirasu” has a much higher permeability compared with the Nichinan formation.
2) Former topographic divide of the old Kimotsuki River basin which is composed of the Nichinan formation and is now covered by “Shirasu” may possibly act as a groundwater divide. In the left bank area of the Kimotsuki River basin, such groundwater divide which can be geologically estimated exists within the Hishida and Tabaru River basin across the topographic divide.
3) The area which may possibly supply groundwater to the Kimotsuki River basin by the watershed leakage is estimated about 47km²; 34km² in the Hishida River basin and 13km² in the Tabaru River basin respectively.
Considering above mentioned hydrogeological data, satisfactory results on the hydrologic balance were obtained. That is, if the estimated amount of the watershed leakage from the Hishida and Tabaru River basin is added to the amount of flow, it comes to approximately coincide with the amount of rainfall in the Kimotsuki River basin.
On the contrary, in the Hishide River basin, the estimated amount of flow from corrected area of this river basin (sabtract 34km² from actual river basin area) might be abequate judging from available amount of river water during irriration season.

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In the period 1973-1975, the hydrogeological studies were carried in the area of the Soraku hill, Kyoto Prefecturure. The conclusion are summarized as follows:
1) The geology of the Soraku hill consist of Sonoha formation and the lower part of the Osaka group. The main aquifers are sand bed and sand and gravel bed of the Osaka group.
2) The artesian wells are about 110 to 120 meters in depth and their discharge is about 700-800m³/day.
From the consideration of land subsidence in Osaka, it is suggested that the unit area discharge of ground water for further development of this area is about 1, 000m³/day/km² or 300, 000m³/year/km².
3) The depth of the basement was presumed from the result of gravity survey. The maximum value in the depth situated near Simoumedani is approximately 240 meters under the ground.
4) Though the quality of shallow wells is bad, that of deep wells is good.

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The relationships between the displacement of the rock mass and its structural control are obtained by the procedure based upon the geological structure.
Results of studies on the geological structures and landslides in Kinki, are as follows:
1) Single fault type 2) Double faults type 3) Triplicate faults type 4) Erosion type 5) Weatering type 6) Bedding plane type 7) Bedding plane & fissure type 8) Earthquake type.

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“Shirasu” is a popular name of non-or slightly welded pumice flow and fall deposits which are widely distributed in southern Kyushu. The deposits are rich in pore space and fissure, accordingly, specific discharge of the “Shirasu” area is generally a range of 0.02-0.04m³/sec/km² in low water season for. the drainage basin of about 100km² or more.
The author measured specific discharges at two hilly districts composed mainly of “Shirasu” in low-water season. Each districts are divided into small units of watersheds of 0.05-1.0km² according to topographic features. As results, contrary to expectation, specific discharges are widely dispersed within a range of 0.003-0.157m³/sec/km². The cause of above-mentioned dispersion considered as below: namely, the ground water of the “Shirasu” area pours out towards the streams not always equal quantity around the ridge but within some definite direction affected by the following factors.
1) unisotropy of permeability caused by unhomogenuity of “Shirasu” deposits.
2) geomorphologic feature of each watersheds.
3) existence of concealed hydrogeologic barrier.
So far as the area studied, the author concluded that dispersion of specific discharge is caused by the existence of concealed hydrogeologic barrier, based on relief of boundary between “Shirasu” deposits and underlying non-pyroclastic sediments presumed from geologic background.
And from the results, it is pionted out the way for presuming concealed geologic structure is clarified from hydro-geologic measurements of specific disharge in low-water season.

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