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Unit area discharge of groundwater, Z(m^3/day/km^2) can be expressed by the following equation, Z=n/AQ^^- where Q^^- is the average discharge (l/sec) of well or spring, A is the area (km^2) of the surrounding terrain having the same hydro-geologic condition at the well site. N/A is called the coefficient of well distribution or of spring distribution. This paper deals with the calculation of Z values for Tokai and Chugoku-Shikoku districts with the amount of free groundwater and with that of artesian groundwater. The Z values of artesian groundwater in those districts were plotted on the inter-section chart, Z-Q^^--n/A diagram, with reference to several well-known land subsidence area. On the diagram, the regression equation based on the method of least squares for 10 sites in the spring area is as follows : log Z=0.772 log Q^^-+2.357 and that for 4 sites in the land subsidence area is log Z=0.890 log Q^^-+2.617 The value of n/A in the land subsidence area was high as 2.5〜4. This result suggests that the land subsidence might be due to the overdraft of artesian groundwater rather than that of free groundwater.