Dissolved major components and oxygen and hydrogen isotope ratios reveal that the groundwaters <30m depth are recharged by the rain at the Uemachi-daichi (uplifted Pleisocene sediments) and by the seawater and riverwater at the western lowland from the Uemachi-daichi of Osaka City. The seawater invades along the rivers into the shallow groundwater at 3km from the coast.
