Treatment of Li Bing Stone Statue in Minjiang River

Li Bing and his son Erlang made a field trip along the Minjiang River, learned about the water conditions and topography, and worked out a plan for harnessing the Minjiang River. In order to make the water of Minjiang River flow eastward, a 20-meter-wide hole was opened in Leiyushan, which was called "Baokou Bottle". The end of the separated Leiyu Mountain looks like a big pile, which is called "left pile" by later generations. In addition, a diversion weir was built in the middle of the river to make the water in the river into two streams, forcing one of them to flow into the bottle mouth. In the process of building the diversion weir, after failing to throw stones in the middle of the river, Li Bing found a new method, which made bamboo workers weave a big bamboo cage three feet long and two feet wide, filled with pebbles, and then sank to the bottom of the river one by one, finally overcoming the rushing river and building the diversion levee. The front end of the levee looks like a fish head, hence the name "fish mouth". It faces the upper reaches of Minjiang River and divides the surging river into two parts. The western share is called Waijiang, which is the positive flow of Minjiang River. Neijiang in the east is the main canal of irrigation canal system, with Baokou at the head, which flows through it and is divided into many large and small canals, forming a criss-crossing fan-shaped water network to irrigate thousands of miles of farmland in Chengdu Plain. Gravel berms are built on both sides of the diversion weir. The one near Neijiang is called the inner diamond dike, and the one near the outer river is called the outer diamond dike, also called the "golden dike". After the completion of the diversion weir, there are few floods and droughts in Chengdu Plain irrigated by Neijiang.

Later, in order to further control the amount of water flowing into the bottle mouth, a flat trough and a "flying sand weir" spillway for flood diversion were built at the tail of the fishmouth diversion dike. The flying sand weir is also made of pebbles in bamboo cages, and the top of the weir is at a suitable height. When the water level in Neijiang is too high, the flood will overflow the Sha Fei weir and flow into the outer river through the horizontal flume to protect the Neijiang irrigation area from flooding. At the same time, due to the vortex effect of water flowing over the flying sand weir into the outer river, the sediment deposition before and after the bottle mouth is effectively washed away. There is a certain proportion of water in the fish mouth. During the spring ploughing season, the water in Neijiang accounts for about 60%, and the water in Waijiang accounts for about 40%. In flood season, when the Neijiang River exceeds the amount of water needed for irrigation, the Sha Fei weir will overflow the Neijiang River. Bottle mouth is the entrance of Neijiang to control water quantity. In order to control the flow of Neijiang, Li Bing and his son stood in the middle of the river like stone men, as a yardstick to observe the water level, demanding that the water level be "inexhaustible and full of shoulders".

Li Bing also made a stone rhinoceros and buried it in Neijiang as the depth standard for repairing dredged sediment every year. The principle of annual maintenance is "deep scouring beach and low weir". "Deep beach scouring" refers to digging the sediment deposited at the bottom of the river deeper to avoid the water in Neijiang being too small to be irrigated; "Low weir" means that the top of the flying sand weir cannot be built too high, so as to avoid poor flood discharge in flood season and endanger the Chengdu Plain. Later generations carved a six-character formula on the stone wall of Erwang Temple built in memory of Li Bing and his son on the east bank of Neijiang, which was very eye-catching. The method of annual maintenance is to intercept Waijiang River with a fork (Mazar) on the west side of Yu Zui in the first frost season with the least annual water quantity, so that all the river water flows into Neijiang, and then dredge the sediment deposited in Waijiang River and its irrigation channels. Around the spring of the following year, the annual maintenance of Waijiang River was completed, the bridge was moved to Neijiang to let the river flow into Waijiang River, and then the Neijiang River was excavated to carry out the annual maintenance of flat channel and flying sand weir. Before Tomb-Sweeping Day, Neijiang was completed in the New Year, the bridge was demolished and drainage irrigation was started. Chacha is a simple and effective temporary interception device. It is a tripod made of three large wooden stakes tied with bamboo ropes, with a platform in the middle, and pebbles are placed in bamboo cages on the platform for stability. Put an appropriate number of rafters in the river, tie horizontal and vertical wood on the water surface, enclose bamboo mats, and cultivate soil outside to stop the water flow and prevent leakage.