The "10 rivers carry 93%" figure quoted above is Schmidt et al. 2017 (Env. Sci. & Tech.). The field has revised it hard since: Meijer et al., Science Advances 2021 (open access, doi:10.1126/sciadv.aaz5803) finds 1,656 rivers account for 80% of global emissions (0.8-2.7 Mt/yr), not 10. Small rivers dominate: 830 rivers under 10 m3/s carry 30% of emissions, while the 33 largest rivers account for ~3%. Worth noting the lead author is at The Ocean Cleanup, so the revision came from inside the project itself.