Study on Groundwater of Chugoku-Shikoku District

Unit area discharge of groundwater, Z of typical groundwater basins in Chugoku-Shikoku District was computed, and the relation between Z and their hydrogeological conditions was inspected. The results are as follows:(1) It seems that there is a mutual relation between Z of confined and unconfined groundwater of Shikoku Setonaikai coastal plain areas, Hirusenbara area and Misato area and Y value. Value, Y is a ratio of total annual precipitation in the catchment area of groundwater basin to the area of groundwater basin.(2) It is also noted to be some mutual connections between Z of Shikoku Setonaikai coastal plain areas and the degree of development of aquifer, especially of gravel bed.(3) Apparent unit area discharge of spring, Z of the North-West area of Mt. Daisen Volcano and Kusama Karst areas shows a linear zonal relationship with discharge average of spring in “Z-Q-n/A” diagram (Fig. 7).(4) Though land-subsidence by over-pumping has not been occurred in Shikoku Setonaikai coastal plain areas, Z of these areas shows higher value than that of typical land subsidence areas in Japan such as Tokyo downtown area, Osaka sea-side area and Niigata coastal plain area. Salt-water intrusion has been occured in some coastal aquifers of Shikoku Setonaikai coastal plain areas. From above results, the author insists to be of importance to compare Z of various groundwater basins with their hydrogeological conditions for the evaluation, further development and the conservation of groundwater resources.