Wow. I don't have much more to add than what Jason already said, other than "Jean de Florette" was obviously never meant to be a stand-alone movie. If you do not see "Manon of the Spring", you do not know the full extent of the story. I rented it from blockbusteronline.com and the disk came with a movie on each side.
I guess I would liken it somewhat to "The Count of Monte Cristo" (book, not the movie) in that you know there will be revenge, but you don't know how terrible it will be until the very end. For all who were pissed off at the old Soubeyran uncle, all I can say is he gets his comeupins, and then some.
Maybe everyone else saw both movies; it wasn't clear to me. I actually fell asleep in "Jean," but I was wide awake for "Manon." They made me a believer in French filmmaking. I'm hesitant to say anymore in case you haven't seen "Manon." It's too good and dark to spoil. The two films could quite possibly be the best "prequel and sequel" ever (and yes, I know that's probably not a correct phrase).