Stage-discharge rating curves using satellite radar altimetry

River discharge is a fundamental quantity that is required to improve our understanding of the hydrological cycle and to inform flood, drought, and water resources management (Gerten et al., 2008; Rajsekhar and Gorelick, 2017; Rao et al., 2020). Discharge monitoring plays a vital role in detecting climatic and environmental change because discharge is an integrated variable reflecting the coevolution of many processes within a basin (Hansford et al., 2020). However, ground-based measurements of discharge are often expensive and not available for many rivers globally. Therefore, spaceborne measurements are pursued as alternatives. 

Recent studies have proposed various methods based on hydraulic equations to estimate discharge from multiple remotely sensed variables, such as water surface elevation (WSE), river width, and slope (Durand et al., 2016). However, such methods generally demand instantaneous observations of several variables. Some other methods rely on one single variable, such as width, WSE, or raw signal reflectance, provided that in-situ discharge data are available to build empirical relationships. 

One widely used approach involves stage-discharge rating curves. Like ground-based methods, these curves estimate discharge by relating river stage (water level or WSE) measured by altimetry to discharge values previously recorded at gauging stations. This approach is straightforward to implement. This study leverages the power of Sentinel-3 altimetry to augment discharge estimates at the global scale. 

We aim to achieve this through two key objectives:

• Developing a global network of rating curves: We will create a comprehensive dataset of stage-discharge rating curves using Sentinel-3 altimetry data.
• Investigating key influencing factors: We will investigate how river characteristics impact the reliability of these curves. Understanding these factors is crucial for optimizing their effectiveness.