Seres — D.3 River Discharge ATBD.

7 Derive discharge from merged products The traditional process to estimate river discharge that uses data from altimetry is here advanced with the contribution of multispectral images and river width to overcome the limits of individual sensors related to the temporal frequency. The merging procedure is carried out through the L3 Merging approach. Details on this approach will be provided in the next version of the document (v2.1). 8 References Altenau, E. H., Pavelsky, T. M., Durand, M. T., Yang, X., Frasson, R. P. D. M., & Bendezu, L. (2021). The Surface Water and Ocean Topography (SWOT) Mission River Database (SWORD): A global river network for satellite data products.

Water Resources Research , 57 (7), e2021WR030054. https://doi.org/10.1029/2021WR030054. Andriambeloson, J. A., Paris, A., Calmant, S., & Rakotondraompiana, S. (2020). Re-initiating depth- discharge monitoring in small-sized ungauged watersheds by combining remote sensing and hydrological modelling: a case study in Madagascar. Hydrological Sciences Journal , 65 (16), 2709- 2728. Belloni, R., Camici, S., & Tarpanelli, A. (2021). Towards the continuous monitoring of the extreme events through satellite radar altimetry observations. Journal of Hydrology , 603 , 126870. Biancamaria, S., Durand, M., Andreadis, K. M., Bates, P. D., Boone, A., Mognard, N. M., ... & Clark, E. A. (2011).

Assimilation of virtual wide swath altimetry to improve Arctic river modeling. Remote Sensing of Environment , 115 (2), 373-381. Bogning, S., Frappart, F., Paris, A., Blarel, F., Nico, F., Picart, S. S., ... & Braun, J. J. (2021). Hydro- climatology study of the Ogoouй River basin using hydrological modeling and satellite altimetry. Advances in Space Research , 68 (2), 672-690. Bogning, S., Frappart, F., Blarel, F., Nico, F., Mahй, G., Bricquet, J. P., ... & Braun, J. J. (2018). Monitoring water levels and discharges using radar altimetry in an ungauged river basin: The case of the Ogoouй. Remote Sensing , 10 (2), 350. Chow, V. T. (1959). Open-Channel Hydraulics. McGraw-Hill Education.

Chow, V. T., Maidment, D. R., & Mays, L. W. (1988). Applied Hydrology. McGraw-Hill Education. [Chapter 10: Open-Channel Flow, specifically sections discussing rating curves and power-law relationships] Clayton, D. (1978) A model for association in bivariate life tables and its application in epidemiological studies of familial tendency in chronic disease incidence. Biometrika 65, 141–151. doi:10.1093/biomet/65.1.141 Elmi, O., Tourian, M. J., Bбrdossy, A., & Sneeuw, N. (2021). Spaceborne river discharge from a nonparametric stochastic quantile mapping function. Water Resources Research , 57 (12), e2021WR030277. Elmi, O., & Tourian, M. J. (2023).

Retrieving time series of river water extent from global inland water data sets. Journal of Hydrology , 617 , 128880. Elmi, O., Tourian, M. J., Saemian, P., and Sneeuw, N. (2024). Remote sensing-based extension of GRDC Discharge time series-a monthly product with uncertainty estimates. Scientific Data , 11 (1), 240. https://doi.org/10.1038/s41597-024-03078-6. Filippucci P., Brocca L., Bonafoni S., Saltalippi C., Wagner W., Tarpanelli A. (2022) Sentinel-2 high- resolution data for river discharge monitoring. Remote Sensing of Environment. , 281, 113255, https://doi.org/10.1016/j.rse.2022.113255. D.3 River Discharge ATBD. Reference:

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