Ground-water development in East St. Louis area, Illinois. Urbana, IL ...

where:
(16)
(17)
(18)
The reach of the streambed, , within the area of influence
of pumping is determined by noting the location
of the points upstream and downstream where drawdown
is negligible (say 0.01). The area of induced infiltration,
A r , is then the product of L r and the average
distance between the river's edge and the recharge
boundary.
The infiltration rate of the stream bed per unit area
can be computed with the following equation:
where:
(19)
Rough approximations of the average head loss, s r ,
due to the vertical percolation of water through the
stream bed can be determined by averaging drawdowns
computed at many points within the area of infiltration.
Values of drawdown within the stream-bed area of infiltration
are computed, taking into consideration the
pumped well and the image well associated with induced
infiltration, with equations 14 through 18.
The average infiltration rate of the stream bed per
unit area per foot of head loss can be estimated by use of
the following equation:
where:
(20)
The infiltration rate of the Mississippi River bed at
three sites was determined from aquifer-test data. The
sites are just south of the confluence of Wood River and
Figure 55. Graph showing the relationship between percent of
pumped water being diverted from a stream and the factor 'f'
the Mississippi River, west of Wood River, and west of
Monsanto. A summary of the results of aquifer tests
and computed infiltration rates are given in table 27. The
infiltration rate near the confluence of Wood River and
the Mississippi River at a river temperature of 33F was
estimated to be 305,000 gpd/acre/ft; the infiltration rate
west of the city of Wood River was estimated to be
36,300 gpd/acre/ft; and the infiltration rate west of
Monsanto at a river temperature of 83F was estimated
to be 91,200 gpd/acre/ft.
Infiltration rates per foot of head loss vary with the
temperature of the river water. Average monthly infiltra-
48