Hydrological Sciences
Flow calculation
- r.carve: Takes vector stream data, transforms it to raster and subtracts depth from the output DEM.
 - r.drain: Traces a flow through an elevation model on a raster map.
 - r.fillnulls: Fills no-data areas in raster maps using v.surf.rst splines interpolation
 - r.fill.dir: Filters and generates a depressionless elevation map and a flow direction map from a given elevation layer.
 - r.flow: Construction of slope curves (flowlines), flowpath lengths, and flowline densities (upslope areas) from a raster digital elevation model (DEM)
 - r.topidx: Creates topographic index [ln(a/tan(beta))] map from elevation map.
 - r.terraflow: Flow computation for massive grids.
 
Groundwater flow
- r.gwflow: Numerical calculation program for transient, confined and unconfined groundwater flow in two dimensions.
 - r3.gwflow: Numerical calculation program for transient, confined groundwater flow in three dimensions.
 
Hydrological models
- r.topmodel: Simulates TOPMODEL which is a physically based hydrologic model.
 
Sediment modules
- r.sim.sediment: Sediment transport and erosion/deposition simulation using path sampling method (SIMWE)
 - r.sim.water: Overland flow hydrologic simulation using path sampling method (SIMWE)
 
Stream modules
- r.stream.angle:
 - r.stream.basins:
 - r.stream.del:
 - r.stream.distance:
 - r.stream.extract:
 - r.stream.order:
 - r.stream.pos:
 - r.stream.stats:
 
Watershed modules
- r.basin.fill: Generates a raster map layer showing watershed subbasins.
 - r.water.outlet: Watershed basin creation program.
 - r.watershed: Watershed basin analysis program.
 
Tutorial: Creating watersheds