Raven is an open source server project offering hydrological modeling and analysis capabilities through the Web Processing Service (WPS) standard. Raven processes can be embedded in a graphical user interface or accessed directly from a programming environment. From Python, birdy WPSClient provides a user-friendly python interface to Raven's WPS processes. Raven was made to help scientists run hydrological modeling experiments with climate change projections. It includes four lumped daily hydrological models (GR4J-CN, HBV-EC, HMETS, MOHYSE) that can be run in multi-model experiments. Meteorological input variables as well as streamflow and storage outputs use the netCDF format. Raven bundles model calibration processes, time series analysis (with xarray), hydrological indicators and frequency analysis (using xclim). On top of this, a database of pre-calibrated model parameters over North America is available to perform model regionalization, allowing simulations in watersheds with no streamflow observations. The properties of custom watersheds can be extracted from a Digital Elevation Model and a land-use database.