CE 473/573 Groundwater
Fall 2007
Comments on homework 2
10. When the boundary heads are fixed and K is homogeneous, the value of K does not
affect the heads; however, by Darcy’s law, the flow will double if K doubles since the
gradient is unchanged. (Make sure to answer all parts of a problem and include all
requested results and graphs.)
11. All groups computed the head as a function of x even though I requested only a sketch.
Two groups produced graphs in which the head increased as x increased. That implies
that the flow is in the negative x-direction. The correct way to think through this
problem is to say that conservation of mass requires the flow to be constant at all
positions in this aquifer. Then by Darcy’s law
Q = −K
dh
A
dx
If Q and A are constants and K decreases, then the gradient must increase. That
is, more driving force is required to achieve the same flow when the conductivity
decreases.