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V� <br /> 1� <br /> 1 <br /> 154 GROUNDWATER HYDROLQCY CRO' <br /> 80 <br /> r so <br /> 1 <br /> Y I <br /> e 40 1 <br /> E i <br /> e 30 j r <br /> i j sQ <br /> p Drawdown I biliz <br /> 20 r" serfe <br /> Inca <br /> to prox <br /> shou <br /> Well 1021CO- in or <br /> o <br /> Fri <br /> 0 5 to 15 <br /> Well discharge,Q,1000 meters;/day <br /> ! Fig.4.30 Variation of total drawdown s.,aquifer loss BQ. Therr <br /> and well loss CQ"with well discharge(after Rorabaugh"). '= straig <br /> b <br /> � y th <br /> ! increases the discharge only 10 percent. When the comparison is - interc <br /> extended to include well loss, however, the effect is significant. _ Ror <br /> Doubling the well radius doubles the intake area, reduces entrance `"'" deterr• <br /> velocities to almost half,and(if n =2)cuts the frictional loss to less ' <br /> than a third.For axial flow within the well,the area increases four <br /> times, reducing this loss an even greater extent. <br /> i It is apparent Heat the well loss can be a substantial fraction of if di. <br /> total drawdown when pumping rates are large, as illustrated by `~` capac. <br /> Fig. 4.30. With proper design and development of new wells (see _ tivity r <br /> Chapter 5),well losses can be minimized.Clogging or deterioration the we- <br /> of well screens can increase well leases in old wells.36 Based on field (Eq.4._ <br /> experience WaltonTO suggested criteria for the well lass coefficient C <br /> in Eq.4.67.These are presented in Table 4.4 to aid in evaluating the <br /> condition of a well. <br /> ( Evaluation of Well Loss. To evaluate well loss astep-drawdown _ so that <br /> pumping test is required. This consists of pumping a well initially <br /> at a low rate until the drawdown within the well essentially sta- <br /> ...... <br />