Overview & Guidance

App Overview & User Instructions

This tool presents the global prediction of rain-dominated catchment behavior in stormflow generation. Users can evaluate ungauged or custom catchments across two primary modules:

HydroBASINS Module

Select an outlet of interest directly on the interactive map provided in the HydroBASINS section to retrieve predicted behavioral classes for dormant and growing seasons, alongside key estimated physio-climatic characteristics.

Dataset Source: Global HydroBASINS database (Lehner & Grill, 2013).

Uploaded Boundaries Module

Upload custom catchment polygon boundaries via the sidebar toggle. Files must be under 5 MB and provided as either:

A ZIP archive containing core shapefile components ( .shp , .shx , .dbf , .prj )
A GeoPackage ( .gpkg ) file

Multiple polygons are supported. Once uploaded, the Uploaded Boundaries section populates an interactive attribute table where specific polygons can be selected for predictions.

Required Citation Policy

If you are utilizing the physio-climatic or stormflow attributes extracted or generated by this application in your research, reports, or datasets, you are required to cite the companion publication listed under the Companion Publication section below.

Disclaimer & Limitations

Dataset Disclaimer

Certain attributes for the original gauged dataset in the companion publication were derived from high-resolution, local data sources (e.g., daily climate time series) rather than aggregated global attribute maps. Consequently, minor inconsistencies may exist between the original published dataset and the outputs generated via this automated global tool.

Operational Limitations & Out-of-Range Warnings

⚠️ Predictions cannot be generated if any of the 27 required attributes are missing (N/A). This may occur if:

Catchment area is too small to compute spatial/topographic features (e.g., slope).
Catchment lies in a region with missing physio-climatic data (e.g., MODIS phenology null zones).

Users are strongly advised to account for uncertainties associated with predicting behavioral classes for catchments with physio-climatic attributes outside the range of trained gauged catchments. Predictions for catchments with snow fraction, aridity index, and/or catchment area outside the training range are automatically withheld.

Companion Publication

Citation: Ameli, A. A., Sharif, H., and McDonnell, J. J. (2026). “A global classification of hydrologic functional diversity in gauged and ungauged catchments”. Nature Water (In Press). https://doi.org/10.1038/s44221-026-00699-6

Abstract: Most of the world’s streams remain ungauged, a longstanding hydrologic challenge. Here we develop a globally scalable, seasonally resolved framework that classifies catchments according to the complexity of how rainfall is converted into runoff across events, yielding three functional types: simple, intermediate, and complex. Applied to over 80,000 gauged and ungauged catchments, it reveals that functional complexity is the global norm: catchments draining 87% of the evaluated ungauged land area are classified as complex in the dormant season, with the number of complex catchments increasing by 63% in the growing season. Africa and much of Asia (except Japan) remain predominantly complex year-round; Europe reaches 94% complex in the growing season; the U.S. Pacific Northwest and Canada’s British Columbia retain simple clusters; and southeastern South America and southeastern Australia show notable transitions from complex to intermediate, demonstrating that catchment functional type is not fixed. Greater urban and agricultural land cover, together with less persistent rainfall, are associated with greater functional complexity. These findings provide a blueprint for prioritizing streamflow gauging in underrepresented complex catchments and for guiding model structural selection, transferability, and prediction in ungauged catchments, ensuring that models are neither simpler than necessary nor more complex than required.