55t W K

r2S 4Tt

Equation 9.8(36) is similar to Equation 9.7(20) for a confined aquifer except that the well function contains the additional term r/A. The values of W(u, r/A) are given in Table 9.8.2.

Walton Method

Walton's solution (1962) of Equation 9.8(36) is similar to the Theis method for a confined aquifer. Plotting s versus t/r2 gives the data curve. Plotting W(u, r/A) versus u for various values of r/A gives several type curves. Figure 9.8.8 shows the type curves. The data curve is superimposed on the type curves to get the best fitting curve. Again, four coordinates of a match point are read on both graphs. The resulting values of W(u, r/A) and s are substituted into Equation 9.8(36) to calculate T. The value of S is obtained from Equation 9.8(37) when u, t/r2, and T are substituted. The value c is calculated from c = A2/T where A is obtained from the r/A value of the best fitting curve.

Hantush's Inflection Point Method

Hantush's procedure (1956) for calculating T, S, and c from pumping test data utilizes the halfway point or inflection point on a curve relating s to log t. The inflection point is the point where the drawdown s is one-half the final or equilibrium drawdown as

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