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WCH Test Anal sis <br /> aquifer occurs as the water table attempts to catch up with the <br /> plozometrle surface established In phase one, A Piot of the <br /> drawdown vs, time data for this portion of a pump test Indicates <br /> that file slops at the curve decreases relative to the Theis curve. <br /> This is a result of additlonn! water becoming availablo, due to <br /> drainage, which a erIs c the measured drawdoy,a in the tiveIi. The <br /> third and last phase Is characterized by coinclden �c of the <br /> tuble with the piezamctric surface produced In phasewater ono. When this <br /> occ"rs, most of the water being removed from story.;e Is trara the <br /> dewatering of the aquifer. A plot of drawdnwn vs. time data from <br /> tills portion of a pump test would have the same shape as the Thels <br /> curve. The calculated specific yield of the aquifer w,)uld be much <br /> higher than the storativity calculated In phase one since a much <br /> greater quantity of water is available via dewatering of ale aquifer <br /> than due to water expansion and compaction of the aquifer. <br /> Neuman (1972) proposed a method that combines till three phases Into <br /> one solution. Ills solution, It stated In a form similar to the equation <br /> for confined aquifers (Eq. [D f,))� is: <br /> 4 <br /> s = — W(u ,'� �R) <br /> 4=T A D ID. 7) <br /> where: <br /> r 2 S <br /> A , <br /> Tt <br /> r 2 S <br /> -- u _ .�y <br /> D Tt <br /> and <br /> r2 <br /> jo <br /> b2 <br /> "i for an isotropic, homogeneous aquifer. Equation 111.7 <br /> 1 can <br /> divided Into two separate equations. One equation provides aesolution <br /> for the early response portion of the pump test (T <br /> and tile other Provides a solution for the late resp nseAportions)of <br /> sire:le pump test (Type D curves - delayed yield). The two equations <br /> s _ _ W(u ,�) <br /> 4YT A [D. 8] <br /> s W(V ,B) <br /> 4vT L3 <br /> 13.7 <br />