It also serves to explain why the sad flashback to Ennis's childhood appears to take place in the most arid and desert-like landscape of the entire movie, a contrast to the rushing waters of Brokeback Mountain and all that they symbolize.
Oh, wow, good catch, Mikaela. That's the scene that I think was filmed in New Mexico (the vegetation and rocks look like northern NM, at least), and every now and then I've wondered why they trekked all the way down to New Mexico to film that scene. I mean, it seems as if they managed to find places to stand in for everything else, even Texas, in Alberta. I haven't been through Ennis's hometown, but at that elevation and in that part of Wyoming, the vegetation should be a bit different, still sagebrush but not so desert-like.
But if they wanted a lack of water to be really symbolic of that memory, well, that makes the choice make more sense.
Katherine:
But anyway: "What's your name?" "Ennis ... Del Mar." (And I love, in the Cassie scene, that odd little half-smile Ennis gives after saying that.)
And that sets up a sad parallel with Jack's encounter with Randall, when Randall talks about getting together to go fishing and everything. Other people are trying to pick up both Ennis and Jack, but the experiences just remind both men of each other.
You know, I like the additions of the Cassie and Randall stories to the movie. They show just how intense the bond between Ennis and Jack was -- even after so many years of being surrounded by other people, it's clear that none of the other options is a satisfying substitute.
As for other repeated lines: Ennis calls Jack "Jack fucking Twist" at the reunion and the 2nd to last camping trip. (And in the lake confrontation? I can't remember.) Jack calls Ennis "son of a bitch" at the reunion, and "son of a whore-son bitch" in the lake confrontation. Terms of affection turned painful.