pysheds

pysheds implements the core DEM hydrology chain — pit filling, depression resolution, flow direction (D8 and D-infinity), flow accumulation, catchment delineation, and distance-to-outlet — as a NumPy/Numba-accelerated Python library with a deliberately small API. Read a DEM, snap a pour point, extract a catchment: about ten lines.

For embedding delineation inside a larger Python application or batch-processing hundreds of outlets, pysheds is the lightest-weight serious option. It doesn't try to be a full terrain suite (no breaching, no lidar); WhiteboxTools complements it where conditioning gets difficult.