Breed might be one of the bigger losers in the genre. It's not totally uncommon for the protagonist to be forced into an accidental promise for a big project beyond their current means. Breed is only the one that's such a huge loser he thinks if he doesn't complete a decades long project in a day he'll be bad mouthed. There's no way with their level of technological development that the people think of this as anything less than a years if not decades long project. Even after finding a source for the river it would probably take years to scout and determine the path the river should take let alone dig that route.