The large number of arithmetic calculation and excessive computer storage required for a numerical solution usually precludes solving the equations in three-dimensional problems for subsurface hydrogeology. Under condition of clear contrast in permeability between the main aquifer and adjacent aquitards, the flow can be assumed to be vertical in the aquitards and horizontal in the aquifer. The analysis of a three-dimensional aquifer system can be reduced to solving two-dimensional equations for each of aquifer. The present paper deals with a quasi three-dimensional flow system concerning the squeeze from storage in the semiconfining layers and the leakage through adjacent semipervious strata. The differential equations for radial flow system in an elastic artesian aquifer with linear leakage were given by JACOB (1946) in early time. This leaky theory was solved in various ways analytically with the vertical recharging or discharging flow through semipervious strata to the main aquifer, but the squeezing from storage in the semipervious layers was neglected. Although the aquitards are relatively low permiabilities, the supplemental released storage water from semipervious strata has an important role in the water balance of a confined groundwater system. The mechanism of squeezing from storage in these semipervious layers was solved by HANTUSH (1960) analytically. To analyze quasi-three dimensional flow systems concerning leakage and squeeze numerically, it is necessary to evaluate two kinds of flow systems leakage and squeeze independently in the process of analysis. Though many of numerous numerical techniques are available for solving parabolic equations, the ADI method was used as the most suitable technique for solving two-dimensional groundwater problems. The merits of this ADI method are following three points which, the field can be treated as a series of one-dimensional strips, the size of matrices can be reduced, and the computer running time can be decreased. Applying this technique to land subsidence problems of the Nanao coastal basin, Ishikawa Prefecture, adequate results were obtained.
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