Hydrological science depends on reliable observations. At the same time, many hydrological datasets are distributed across numerous national and regional services, each with its own access routes, documentation, and terms of use. This fragmentation can make it difficult to clearly document where data come from and to reproduce data retrieval in a consistent way.
To provide more transparent and reproducible access to hydrological observations, GRDC has developed hydrodownloadR. The R package offers a standardized way to discover hydrological stations and download daily time series such as discharge, water level, water temperature and selected water-quality parameters directly from public national and regional APIs.
Transparency in data retrieval is crucial because hydrological assessments and scientific results must be explainable and verifiable across institutions. This is particularly relevant for the annually released WMO State of the Global Water Resources Report, for which GRDC provides data. The hydrodownloadR package supports data retrieval workflows for both routine GRDC data updates and the WMO report. However, the package can also benefit users who require stations that are not yet included in the GRDC database. In such cases, the package provides a straightforward way to access time series directly from the original provider while keeping the data source explicit.
It is important that hydrodownloadR, where available, highlights licensing and terms of use information for each API. Furthermore it is designed to access services responsibly by avoiding excessive requests. Nevertheless, users remain responsible for complying with the providers’ terms of use and citation requirements. Coverage and available parameters depend on the underlying public APIs and their data policies.
Call to action: If you know a public hydrology API or you operate one, please share with us the documentation link, licensing information, terms of use and, if possible, stable endpoints. Also, if you encounter errors or unexpected behavior, please report them via the project’s GitHub issue tracker so we can address them efficiently. This will help to further improve the package and optimize the discoverability and accessibility of hydrological data.
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