Research and improvement of water metering structures for irrigation systems with non-steady flow conditions in agricultural water use

This article examined the problem of improving the accuracy of water metering at water-metering facilities in irrigation systems operating under variable head conditions and subject to intensive siltation. The relevance of this research stems from the need to ensure accurate water flow measurement under unstable hydraulic conditions and the accumulation of bed sediments, which significantly affect the reliability of the structures and the efficiency of water resource allocation. The accuracy of water metering is of vital importance to agriculture, as it affects compliance with irrigation regimes, the rational use of water and the sustainable water supply to the agricultural sector. Insufficient measurement accuracy can lead to water wastage, disruption to irrigation schedules and reduced crop yields. The aim of this study was to develop and provide a hydraulic justification for an improved diaphragm design that ensures measurement stability and reduces the impact of sediment. The study utilised methods of hydraulic calculation, comparative design analysis and modelling of the structure’s operation under various flow regimes and head levels. The influence of the orifice geometry, the position of the bottom opening and the diaphragm configuration on the flow pattern and sediment accumulation processes was assessed. The results showed that, to improve the accuracy of water metering, it is advisable to use two types of diaphragm: a flat plate with an adjustable bottom opening and a design with a fixed opening. It was established that the adjustable opening reduces silting, prevents the cross-section from becoming blocked and stabilises the flow characteristics. The design with a fixed orifice is effective under stable operating conditions. Calculation data confirm a reduction in measurement error, an increase in the stability of the flow coefficient and an improvement in the long-term operational reliability of the structure. The practical value of this work lies in the ability to adapt water metering units to various conditions without complicating the design. The proposed solutions contribute to improving water use efficiency and enhancing water distribution management in irrigation systems