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z ...� Fn ... s „r. szzg - "iS °;` w _ 3` • s"'k.: �a da x r Pon i- J , t 1S2 GROUNDWATER HYDROLOGY ? CROtJ" .� Hsntush25-" and others.37,39,45 Although evaluating the effects is complicated except for the simplest cases, common field situations canny often reduce the prpctical importance of partial penetration.* One inves occurs where an obsr;vation well is located more than 1.5 to 2 times t sides. the saturated aquifer thickness from a pumping well,In this situation TO the effect of partial penetration can be neglected for homogeneous may and Isotropic aquifers. Another applies to many alluvial aquifers with pronounced anisotropy. Here the vertical flow components t become small,thereby enabling a pumping well to be approximated wherf as a fully penetrating well in a confined or leaky aquifer with a co saturated thickness equal to the length of the well screen, condi ondi Well Flow for Special Conditions A variety of solutions to well flow problems have been derived so tha for special aquifer.pumping,and well conditions.=3,33 Inasmuch as these are of less general application than those outlined heretofore and Involve more extensive mathematical treatment, they will be There omitted here.It is worth noting,however,that solutians have been the fo obtained for the following special conditions: Cor. t.Constant well drawdown?43 betwe 2.Varying•cyclic,and intermittent well discharges.22,4r•.s.U.63.ca can be 3.Sloping aquifers.23 ables 4.Aquifers of variable thickness." small., 5.Two-layered aquifers.�s.32,51 &Anisotropic aquifers.r3•:s•29•30.72 7.Aquifer conditions varying with depth 47.34 8 Large-diameter wells.42,73 _ 9. Collector wefts(see Chapter 5)'-4•13 10. Wells with multiple-sectioned well screens.°' Characteristic Well Losses The drawdown at a well includes not only that of the logarithmic drawdown curve at the well face,but also a well foss caused by flow through the well screen and flow inside of the well to the pump Intake.Because the well loss is associated with turbulent flow,it may — be indicated as being proportional to an nth power of the discharge, as Q".where n is a constant greater than one.Jacob"suggested that a value n =2 nhpointed t;ght be reasonably assumed,but Rorabau s3 M21 z g ..�_• out that n can deviate significantly from 2. An exact value for n 'It should be noted that any well with 85 percent or mom open or screened hole in the saturated thickness may be considered as fully peaetrauaa. t.