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' tic t lU Mb 1 2U M 1tv ltr A VLUvlh5 No .i A r DU/04 <br /> point is highly sensitive to the anisotropy of the aquifer. The length of the screen section <br /> is of small importance within usual proportions (as described above). The knowledge of <br /> the distance (S) from the stagnation point can be used to determine the positions of <br /> measuring equipment The operation of a UVB can also be supervised using depth- <br /> dependent measurements between the stagnation point and the well <br /> The sphere of influence of the circulation around a UVB at sites with natural <br /> groundwater flow is of special interest. This sphere of circulation is limited in a quite <br />' different way than at a site with absence of natural flow (Fig. 9a) as can be seen in <br /> Figures 3b, 3c, 4b, and 7. In the direction of natural groundwater flow, this sphere has <br /> a mammum expansion of (S) (see Fig. 12) to the upstream and downstream sides. <br /> Normal to this direction, the mammum radius of the sphere of circulation is <br /> approximated by (B$+BT)/4 (Fig. Ila), and, in the case of several wells in one line, by <br />' D/2 (Fig.11c). <br /> Figures 9, 11, and 12 can be used for the dimensioning of a UVB or UVB field <br /> when the parameters KH/K„and Q/(Hzv) can be estimated, where Q depends on the well <br />' size and on the additional pump. For an irregular well field, a layered aquifer, or special <br /> critical cases, numerical calculations can be performed. <br /> S I a . <br /> H H <br /> 01 KH =10 <br /> d3 Kv <br /> 2s al KH =5 <br /> 03 � K„ <br />' i s Q1 KH =1 <br /> Q3 Kv <br /> CLS <br />' 00 5 >d 15 20 25 :0`:5 L4 LS SO <br /> H= <br />' Figure 12. Upstream distance (S) of the stagnation point from the well aids. <br /> I <br />