CE 473/573 Groundwater
Fall 2010
Comments on homework 3
16. Be sure to subtract hbot , the elevation of the aquifer bottom, from the water table
elevations. The challenge in part d is to determine where the water table enters the
lower soil unit, x = xc , say. Recognize that the head at x = xc is b2 . Then the flow
in the right unit is
b2 − (hL − hbot )2
w.
Q2 = K 2
2(L − xc )
The flow in the left unit is
Q1 = K
(h0 − hbot ) − b2
(h0 − hbot )2 − b22
w + (K2 − K1 )b2
w.
2xc
xc
Equate the two flows to find xc . I get xc = 612 m.
17. The key to part b is to realize that the total flow is simply the recharge rate multiplied
by the horizontal area of the aquifer. For part c, if there is a groundwater divide, the
flow at x = 0 is negative. Therefore, the limiting case for no groundwater divide is
that the flow at x = 0 is zero. Use that information to find the recharge rate.
18. I wanted the flow over the entire length of line A-A . Therefore, the two end sections
should have a width of 1500 m.