《汉书·志·沟洫志》
王莽的时候，征召能治理黄河的人有一百来人，其中大致比较突出的有长水校尉平陵关并说： 黄河决口一般常在平原、束郡左右，它的地形低下而土质疏松。
王莽时，征能治河者以百数，其大略异者，长水校尉平陵关并言： 河决率常于平原、东郡左右，其地形下而土疏恶。
During Wang Mang's reign, more than 100 people were recruited to manage the Yellow River, among whom Changshui Lieutenant Pingling Guan was the most outstanding. Pingling Guan said: The Yellow River often breaches in the areas around Pingyuan and Boshun, because the terrain there is low and the soil is loose.