Research on Real-Time Flow Online Monitoring Technology Using Multi-Angle Inclined Deployment of H-ADCPs

In response to the challenge of limited accuracy in flow online monitoring under complex hydraulic and flow conditions, this study proposed a multi-angle inclined deployment technology using horizontally mounted acoustic doppler current profilers (H-ADCPs). By installing multiple H-ADCP devices with different frequencies at varying tilt angles along the same monitoring cross-section, a multi-angle collaborative observation system was established, together with a combined computational and analytical model. This system effectively enhanced the representativeness of index velocities and the precision of discharge measurement results, thereby providing improved adaptability to variable backwater effects, low-flow conditions, and other complex hydrological situations that commonly affect river monitoring accuracy. By taking the Zhicheng Hydrological Station as a case study, two ChannelMaster-type H-ADCPs, operating at 600 kHz and 300 kHz, were deployed in a combined multi-angle inclined configuration. A long-term comparative monitoring campaign was carried out from January 10 to September 17, 2024, to evaluate the performance of this technology. The study focused on comparing the accuracy improvements achieved by the dual-device combined monitoring scheme against two independent single-device monitoring schemes. Results indicate that when both H-ADCPs adopt an optimal index velocity cell range of 5~30, the correlation coefficients (R2) between the index velocity and the cross-sectional mean velocity for the dual-device combined scheme and the two single-device schemes are 0.990 3, 0.989 3, and 0.988 0, respectively. The regression fitting and calibration model accuracy of the dual-device synchronous monitoring configuration are overall superior to those of either single-device system, demonstrating that multi-angle inclined deployment can significantly enhance both the representativeness of index velocity and the robustness of the flow-velocity relationship model. The calculated flow processes derived from both the dual- and single-device schemes exhibit strong agreement with the compiled discharge data, with relative runoff volume errors of -0.36%, -0.66%, and 1.25% during effective monitoring periods. Furthermore, under typical high, medium, and low water level conditions, the maximum errors of inverted runoff volume during representative periods are 0.76%, -1.33%, and 2.84%, respectively, confirming that the proposed discharge inversion model maintains good stability and consistency across varying hydraulic conditions. Overall, the multi-angle inclined H-ADCP-based flow online monitoring technology integrates both multi-device and single-device configurations that are independently functional yet mutually complementary. This arrangement enhances the continuity, reliability, and fault tolerance of hydrological data acquisition. Consequently, it provides a practical and effective technical pathway for improving the accuracy, stability, and long-term reliability of flow online monitoring systems at hydrological stations, especially in rivers influenced by variable backwater, sediment transport, and other complex flow dynamics.