Why does Noah decide to stay behind? How will he survive?

Noah falls in love with the clear water of the Colorado River and decides not to follow his family. He says he will fish for food.

It ain't no use. I was in that there water. An' I ain't a-gonna leave her. I'm a-gonna go now, Tom—down the river. I'll catch fish an' stuff, but I can't leave her. I can't."