基于水位流量关系的流量估算不确定性分析

针对现有水位流量关系线型物理机制不强及流量估算不确定性来源考虑不充分问题,以北江流域石角水文站为例,推导该测站水位流量关系,基于BaRatin模型评估流量测量误差及率定样本选取对估算流量不确定性的影响。发现河槽控制宽浅矩形断面水位流量关系为幂函数,其系数可用糙率、河宽、比降表达,指数为定值5/3;考虑流量测量误差后高水估算流量总不确定性减小32%;率定数据增加1倍、3倍,高水估算流量总不确定性减小12%、34%。结果表明:①水位流量关系模型建立方法可推广至多类型测站;②高水测量误差对率定精度影响较大,建议提高高水流量测量精度;③现有实测水位与流量数据存在信息冗余,主要存在于低水数据中,本方法可减少率定数据使用,降低整编成本。

Uncertainty analysis of estimated discharge based on stage-discharge rating curves

To address the problems that the physical mechanism of the stage-discharge relationship is not clear and the uncertainty sources of estimated discharge is not adequately considered, current study used the Shijiao hydrological station of the North River basin as an example to derive the stage-discharge relationship. Based on the BaRatin model, current study evaluated the discharge measurement error and the effect of the calibration sample selection on the uncertainty of the estimated discharge. It was found that the stage-discharge relationship for the wide and shallow rectangular section of the river channel is a power function, where its coefficient can be expressed by roughness, river width, and energy slop, and the index is a constant value of 5/3. The total uncertainty of the estimated discharge decreases by 32% when considering the discharge measurement error. Doubling (Tripling) the samples drops the total uncertainty of the estimated discharge by 12% (34%). The conclusions of this study are:① The method of establishing the stage-discharge relationship here can be extended to different types of hydrological stations; ② The high water measurement error has significant impact on the calibration accuracy, and it is recommended to improve the high water flow measurement accuracy; ③ Information redundancy exists in the measured data, particularly in the low water measurements. The proposed method requires less calibration data, which can reduce the cost of discharge compilation.