Comparison Studies About The Ultrasonic Flow Meter's Application And Velocity Instrument In The Flow Measurement Of The Large-scale Irrigation Districts

The implementation of water-saving measures is very necessary because of the shortage of water resources in our country. As a major area of water uses, irrigation district is the key area of water-saving. At present ,the phenomenon that farmland irrigation water was wasted largely is more serious, the considerable part of water quantity irrigated might be wasted by poor irrigation water management. Using water according to plan is the core content of irrigation water management, that is, according to the consumptive use law of crops, water quantity irrigated should be controlled and distributed to meet the crop's water needs timely and economically. Generally speaking, the water-saving potential of irrigation water management might account for above 50 per cent of various water-saving measures. So, the construction of the flow-measuring facilities in irrigation districts is indispensable means in realizing water-saving and improving management capability.Flow measurement is one of the important contents of irrigation water management. Because flow measurement is the basic means of water-saving irrigation and scientific management, so we should pay more attention to it. In addition, with the growing scarcity of the water resources, the requirement of flow-measuring precision should be getting higher and higher. Moreover, scientific management would demand the automation and digital of flow-measuring facilities in irrigation districts. Yet, the requirements of precision, automation and digital of flow measurement have not been satisfied by the traditional flow-measuring method such as velocity instrument. Ultrasonic flow measurement is a new technology, it has overcome the limitations of the traditional flow-measuring technique which doesn't have satisfying precision and doesn't realize real-time recording process, also its measured data is difficult to deal with and so on. And ultrasonic flow measurement has unique advantages. In recent years, with the development of the large-scale irrigation information establishment, ultrasonic flow meters have been applied to the flow measurement of open channels so as to realize the real-time monitoring of the hydrological data in many irrigation districts. So far, there are less comparison studies about ultrasonic and velocity instrument in the flow measurement of irrigation districts. Therefore, in order to promote the application of ultrasonic flow measurement in open channels and be able to build digital irrigation districts as well as realize the optimal allocation of water resources and modern management of large-scale irrigation districts as soon as possible, the comparison studies about ultrasonic flow meter's application and velocity instrument in the flow-measuring of large-scale irrigation districts should be conducted systematically, which also has great practical significance.This studies choose Gaoya Reservoir irrigation district and Rizhao Reservoir irrigation district as study sites. Firstly, through the installation of the ultrasonic flow meters, the flow measurement method of non-uniform flow in the open channels had been studied: (1) the water depth, flow velocity, flow discharge and accumulative discharge of the water-carrying section could be real-time monitored by the five-path ultrasonic flow meter in Xujiamiao station of Gaoya Reservoir irrigation district; (2) the water depth, flow velocity, flow discharge and accumulative discharge of the water-carrying section could be real-time monitored by the five-path ultrasonic flow meter in Majialing station of Rizhao Reservoir irrigation district. Secondly, the ultrasonic flow meter and the velocity instrument have been used to measure the flow discharge at the same water-carrying section by means of synchronous method. Finally, based on the theory of mathematical statistics, the correlativity of the measured date by both the ultrasonic flow meter and velocity instrument could be analyzed. The main results can be concluded as follows: Under the condition of stringent verification(α= 0.01), the linear correlative coefficients (r=0.902 ~ 0.954)of the measured date by both the ultrasonic flow meter and velocity instrument were bigger than the threshold( r_α= 0.6226). The measured date show highly positive correlation. The straight lines of linear regression equations also close to the theoretical straight lines. Furthermore, the ultrasonic flow meter possesses higher precision and stronger applicability than the velocity instrument. Also ultrasonic flow meter does not affect the flow state of open channel, and it can realize the real-time monitoring of hydrological data. Moreover, it is convenient to the implementation of flow measurement and data processing,etc. So, ultrasonic flow meter should be promoted properly as an accurate method of the open channel flow measurement in the information establishment of large-scale irrigation districts.