"Let judgment run down as waters" means let condemnation and punishment pour down on sinners

Amos 5:24 pairs "judgment" directly with "righteousness": "let judgment run down as waters, and righteousness as a mighty stream." That parallel is the tell: Amos wants abundant, unstoppable justice in Israel's courts and streets, not abundant condemnation. "Judgment" in this older, broader sense means the fair administration of a case, the same sense preserved in "the judgment of Solomon" or a courtroom "judgment."

Modern English has narrowed "judgment" toward its negative pole: "don't judge me," "the judgment of God" as a synonym for wrath, so a reader who only knows that sense misses that Amos is demanding more fairness, not more doom.