  These are notes that I compiled while studying the equations of long-range
groundwater flow for my first paper. By "long-range," I mean horizontal
distances that are significantly greater than the vertical thickness of the
aquifer, in addition to some other assumptions discussed below. None of this
material constitutes original development of important new equations, but it
might be useful to someone learning about simplified models of groundwater flow
for numerical solution.
  I start from Darcy's Law, reminding myself how to formulate the vertically
averaged conservation law for groundwater flow. Then I discuss some ideas about
how to solve the flow equation numerically. After that, I go through some cases
where the hydraulic conductivity is a simple function of the vertical
coordinate and the the steady-state flow equation can be simplified. Finally,
there is a very short discussion of the transient case.
