Robinson DC Pump
From Andy Halbert - The Robinson DC powered submersible well pump can be found here: http://www.solarpumps.com/products.html (dead link) You would want the smaller of the two about half way down the page " Dual piston BL40D (535240)" It runs off of DC power from 12 - 40 volts and will fit down the 4" well you have. The larger quad piston pump is too large to fit in the 4" well. I would put that in the well you have and pump the water over into the old rain catchment system and see how far that gets you. If you end up needing a new well the Robinson pump can be used in it. There are a few lower cost DC powered well pumps out there but they seem to fail within a matter of months whereas the Robinson last much longer and is rebuildable. Grundfos makes the best DC powered submersible well pumps but they cost twice as much as the Robinsons.