Channel flow metering mainly includes the water level method and the flow velocity area method: The water level method is used to measure the water level upstream (or upstream and downstream) of a building by measuring the amount of water and converting it into flow by an empirical formula or experimental curve. Therefore, the water level flow meter needs to build a volumetric water structure, and the accuracy is not high. When the water head difference along the channel is small, the water quantity building will produce head loss and affect the channel water; on the other hand, the equivalent water structure is built near the downstream of the building. When there are flood gates and other water blocking structures, submerged outflows will form at the volumetric structures, and the measurement accuracy will be greatly reduced. The flow rate area rule does not require the construction of a volumetric structure, and the flow rate is obtained by measuring the cross-sectional area of the cross-section (actually, the cross-sectional area of the cross-section is obtained by converting the measured water level) and the cross-section flow rate, and the accuracy is high. The influence of the downstream supporting water. Flow rate area flowmeters mainly include ultrasonic time difference flowmeters and ultrasonic Doppler flowmeters. Since ultrasonic time difference flowmeters and ultrasonic Doppler flowmeters used to be dominated by foreign products in the past, there are almost no similar products in the country. Therefore, the cost is high, and it is difficult to popularize such products by installing them on major trunk canals and important branch canals. Generally, the water level flow meter (water level meter + water volume building) is used as the main equipment for channel measurement. The HOH-L-01 Doppler Ultrasonic Open Channel Flowmeter developed and produced by Beijing Jinshui Science and Technology Co., Ltd. has the same technical performance as foreign products, and has the advantage of anti-shelving and anti-theft protection, especially its low price. The sum of the cost of the water level meter and the water meter building is the first choice for open channel flow meters.