Page 130 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

JWCL344_ch03_061-117.qxd 8/17/10 7:48 PM Page 92

92 Chapter 3 Water Sources: Groundwater

Well Stream

Undisturbed
water level
Cone of depression
or real well with
supply from stream
a
(a)

Q
Cone of
impressional

Recharging
Buildup component image well
Undisturbed water level s
of image well i
Discharging Q
Real well Cone of depression
for real well with
s r
supply from stream
Drawdown
component of
Cone of depression
for real well with real well
supply from stream Center line of stream
(b) a a

Figure 3.10 Application of the Method of Images to a Well Receiving Water from a
Stream (idealized). (a) Real System. (b) Equivalent System in an Infinite Aquifer.

Drawdown at 1,500 ft (5 m) from the stream:
r 1,500 ft
r i a r 1,000 1,500 2,500 ft
s 11.55 log(2,500>1,500) 2.56 ft
Drawdowns at other points can be calculated in a similar manner.
The results are shown in Fig. 3.10.
Solution 2 (SI System):
In the region of interest, the use of semilogarithmic approximation is valid:
s = (0.366 Q>T) log (r i >r)
s w = (0.366 Q>T) log (2a>r w )
0.366 Q>T = 0.366 * 3,815>397.4 = 3.5 m