Symbolism, Imagery, Allegory
Before her death, Ma suggests that Daddy dig a pond near the windmill to create a new water source. Daddy quickly shoots down this idea, but after Ma's death, we see him actually start putting the plan into action—despite everyone in town thinking he's gone nuts, he begins digging a giant hole.
But is a pond really his original intention? Again, the fact that we're reading Billie Jo's diary introduces some ambiguity about the actions of others. When he begins digging the hole in chapter fourteen of part three, not long after Ma's death, Billie Jo seems to agree with the general consensus of insanity and wonders if he's really thought through what he's doing. When the cancerous spots begin showing up on Daddy's skin, she develops a new, much darker theory:
My father's digging his own grave / he calls it a pond / but I know what he's up to (97.4)
The pond may carry an air of darkness about it at first, but fortunately, that's not what's really going on here. When Daddy meets Billie Jo at the train station, he tells her that the pond is finished and that he has plans to fill it and release catfish into the water. For the first time, the hole begins to take on an actual shape and plan for the future, and Daddy accomplishes this goal.
As Louise and Billie Jo look at the pond, Louise muses, "A hole like that says a lot about a man" (104.6). Although the hole begins as a symbol of grief and death—digging it is a sort of way for Daddy to dig deep into the pain he feels over losing Ma—the new life it brings forth demonstrates Daddy's journey out of grief and the harsh circumstances of the land.