Measurement of Mountain River Discharge Based on UHF Radar

River discharge is an essential hydrological index of the global water cycle and is important for flood and drought forecast. Ultrahigh frequency (UHF) radar has gained much attention since it can remotely retrieve river discharge from the surface flow velocity measurement in real-time and all-weather condition. However, it becomes challenging for the mountain river case where the water level changes more significant than that of the plain river due to the deep-narrow channel, which breaks the previous empirical relationship between surface flow velocity and discharge. In this letter, an improved index-velocity method is proposed to address this issue. Through modeling the nonuniform variation of the cross-sectional area with water level, a more accurate surface flow velocity–discharge relationship is established. Experimental results show that the proposed method produces higher calculation accuracy than that of the previous methods, which enlarges the applicable scenario of UHF radar in discharge measurement.