《史记·八书·河渠书》
而鄃县在黄河以北，黄河决口水向南流，鄃县没有水灾，收成很好。
鄃居河北，河决而南则鄃无水灾，邑收多。
And Guan county was north of the Yellow River, and the Yellow River burst open, and the water flowed south. Guan county didn't have any flooding, and it obtained good harvests.