A first continuous and distributed satellite-based mapping of river discharge over the Amazon

Victor Pellet (1) , Filipe Aires (1) , Dai Yamazaki , Xudong Zhou , Adrien Paris

1 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique

River discharge integrates many water-related processes over land, it is crucial for understanding inland water. Unfortunately, in situ measurements are very sparse at the global scale. This paper presents a totally new approach for the mapping (i.e. spatially continuous estimate) of the river discharge based on satellite observation of hydrological variables and the water budget balance. First continuous satellite estimate of three water components (precipitation, evapotranspiration, and total water storage change) are corrected at basin scale using river discharge from a few gauge measurements. Secondly, the water budget is balanced at the grid level using flow direction for horizontal water exchange. This new approach is therefore based solely on satellite products and in situ measurements without the use of any dynamical model (except river map). The methodology is evaluated in interpolation mode between successive gauges (median KGE is 0.8) and extrapolation mode over small confluent rivers (mean KGE is 0.6), to be compared to 0.6 and 0.4 for a river dynamic model such as CaMa-flood. The spatially continuous river discharge shows a good agreement with altimetric water surface level (WSL, median correlation of anomalies is 0.6) and surface water extent satellite estimate (correlation of anomalies is up to 0.7 over rivers with floodplains). This suggests that timing of flood and low flow is fine. A comparison with the hydrological model CaMa-flood shows the benefit of such a continuous product to investigate model differences at high or low flow, as well as early flow peak modeling. While the spatial pattern of extreme events cannot be well represented only by in situ gauges information, our study shows the added value of the mapping to better describe these events. As hydrological application, our method can be used in synergy with all the altimetric stations to create discharge-WSL pair data, which will benefit to advanced applications.

Mots clés: 86A32; 86A22

Domaines: Planète et Univers [physics]

Victor Pellet, Filipe Aires, Dai Yamazaki, Xudong Zhou, Adrien Paris. A first continuous and distributed satellite-based mapping of river discharge over the Amazon. Journal of Hydrology, 2022, 614, ⟨10.1016/j.jhydrol.2022.128481⟩. ⟨insu-03851596⟩