Caravan

Caravan, initiated by Frederik Kratzert and collaborators, standardised what CAMELS started: a single open dataset of catchment attributes, meteorological forcing (ERA5-Land derived) and observed streamflow across thousands of basins worldwide, in one consistent format — plus the open pipeline for the community to extend it, which regional groups have done enthusiastically.

If you train or benchmark hydrological models — machine learning or conceptual — Caravan is the closest thing the field has to a common benchmark substrate. It pairs naturally with NeuralHydrology, and its community extensions keep widening coverage beyond the original countries.