The purpose of this study is to clalify the characteristics of groundwater and base runoff small basins composed of relatiuely unconsolidated sediment of the Osaka group. The auth in carried out observations of groundwater levels, stream discharges, and precipitation fro orm middle June,1975 to late March,1976.
At first, the variations of groundwatr level and the characteristic of base runoff are studied. There are two aquifers in a basin. The groundwater levels in a main aquifer do not always reflect the rainfall pattern. The groundwater level in the main aquifer is found to be proportional to the amount of base runoff during dry periods. From the change in the height of groundwater storage and the groundwater runoff from the main aquifer, the amount of groundwater recharge is estimated weekly, and the characteristics of base rnuoff relative to the groundwater recharge are examined.
The base runoff is found to change according to the magnitude of groundwater recharge, and does not necessarily decrease exponentially during dry periods.