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3.13 Aquifer Boundaries 93

Drawdown at the well,
a = 304.8 m
r w = 610 mm>2 = 305 mm = 0.305 m
s w = 3.5 log(2 * 304.8>0.305) = 11.55 m

Drawdown at 152.4 m (or 500 ft) from the stream:
r = 152.4 m
r i = a + r = 304.8 m + 152.4 m = 457.2 m
s = 3.5 log(457.2>152.4) = 1.67 m
Drawdown at 457.2 m (or 1,500 ft) from the stream:
r = 457.2 m
r i = a + r = 304.8 m + 457.2 m = 762 m
s = 3.5 log(762>457.2) = 0.78 m
The results are shown in Fig. 3.10.

For a well located near a stream, the proportion of the discharge of the well diverted
directly from the source of recharge depends on the distance of the well from the recharge
boundary, the aquifer characteristics, and the duration of pumping. Figure 3.11 shows an
inflatable rubber dam that is inflated seasonally (late spring to late autumn) to raise the
river stage by 3 m. The higher stage allows greater pumping rates to be maintained in the
collector wells that supply water to Sonoma County residents in Maui, Hawaii. The contri-
bution from a line source of recharge and distribution of drawdown in such a system can be
evaluated and are extremely useful in determining the optimal location of well fields.
The problem of recirculation between a recharge well and a discharge well pair is of
great practical importance because of the use of wells (or other devices) for underground

Figure 3.11 Inflatable Rubber Dam (Courtesy USGS)