Abstract. This paper presents Shyft, a novel hydrologic modeling software for streamflow forecasting
targeted for use in hydropower production environments and research. The software enables
rapid development and implementation in operational settings and the capability to perform
distributed hydrologic modeling with multiple model and forcing configurations. Multiple models
may be built up through the creation of hydrologic algorithms from a library of well-known
routines or through the creation of new routines, each defined for processes such as
evapotranspiration, snow accumulation and melt, and soil water response. Key to the design of
Shyft is an application programming interface (API) that provides access to all components of the
framework (including the individual hydrologic routines) via Python, while maintaining high
computational performance as the algorithms are implemented in modern C++. The API allows for
rapid exploration of different model configurations and selection of an optimal forecast
model. Several different methods may be aggregated and composed, allowing direct intercomparison
of models and algorithms. In order to provide enterprise-level software, strong focus is given
to computational efficiency, code quality, documentation, and test coverage. Shyft is released open-source under the GNU Lesser General Public License v3.0 and available at
https://gitlab.com/shyft-os (last access: 22 November 2020), facilitating effective cooperation between core developers, industry, and
research institutions.