River Discharge Inversion Algorithm Based on the Surface Velocity of Microwave Doppler Radar

• Published in: Remote sensing (Basel, Switzerland) Switzerland), 2023-10, Vol.15 (19), p.4727
• Main Authors: Chen, Zezong, Wang, Tao, Zhao, Chen, He, Zheyuan
• Format: Article
• Language: English
• Subjects: Accuracy; Algorithms; Antennas; Doppler effect; Doppler radar; Efficiency; Hydrology; Methods; microwave Doppler radar; non-contact method; Radar; Radar meteorology; Radar systems; River beds; River discharge; river discharge measurement; River flow; Rivers; Root-mean-square errors; Safety equipment; Shear stress; Surface velocity; Velocity; vertical velocity distribution; Water depth; Water discharge
• ISSN: 2072-4292; 2072-4292
• DOI: 10.3390/rs15194727

Non-contact methods, which are of great significance to the measurement of river discharge, can not only improve the efficiency of measurement but can also ensure the safety of equipment and personnel. However, owing to their inherent drawbacks such as the requirement of riverbed topography measurements and the difficulty in determining hydrological parameters such as equivalent roughness height, velocity index, etc., there are still challenges for measuring river discharge with high levels of efficiency and accuracy using non-contact methods. To overcome the aforementioned challenges, a new river discharge inversion method is proposed in this paper. In this method, vertical velocities are divided into inner and outer region velocities which can be described by the logarithmic law and the parabolic law, respectively. Applying the river surface velocities collected by microwave Doppler radar and the vertical velocity distributions, the water depths are estimated according to the continuity of the vertical velocities and the shear stresses, and then, the river discharges are obtained by the velocity–area method. The proposed method not only has a simple formula but also comprehensively considers the influence of different hydrological conditions, making it suitable for different river widths and water depths. In this paper, surface velocities collected by microwave Doppler radar on the Yangtze River and the San Joaquin River are used to invert the river discharge, and the results show that for wide–shallow, wide–deep, and narrow–shallow river conditions, the mean percent error (MPE) values of the discharges invertedby the proposed method are 3.91%, 3.82%, and 3.6%, respectively; the root mean square error (RMSE) values are 4.53%, 5.19%, and 4.81%, respectively; and the maximum percent error (MaPE) is less than 15%. The results prove that the proposed method can invert the river discharge with high efficiency and high accuracy under different river widths and water depths without measuring water depth in advance, making it is possible to automatically measure the river discharge in real time.