Dujiangyan is located in guanxian, the middle reaches of Minjiang River in Sichuan Province. The upstream water flows quickly. In guanxian, the terrain became open, and the slow flow of water led to sediment deposition.

Qianyuzui diversion dike is used to divert water, which is divided into Neijiang and Waijiang rivers.

Dig a bottle mouth to irrigate Chengdu Plain in Lidui Mountain, Neijiang.

Build a low weir on the opposite side of the bottle mouth to form a flying sand weir, control the height of the water surface, adjust the water inlet of the bottle mouth, and return the sediment at the bottom to the outer river.

Every year, the floodplain of the diversion tributaries should be deeply washed to keep the diversion flow in a certain proportion.

Low water level weir refers to flying sand weir, which returns water above a certain level to the main stream of Waijiang River when the water volume is large.

Every year, the sand and gravel deposited on the flying sand weir should be removed to restore the weir height to the original water level.

This is the meaning of "deep scouring beach, low weir" Now many people use this sentence in management to lower their posture, empty their minds and meet new challenges.