QGIS is viewed as a software for the spatial data processing to create the input data for a hydrogeological modeling as HEC-HMS or RS-Minerve. But, are there any hydrological software that can run on the QGIS interface? There are some half answers and complete answers that we will answer in this article.

Half answers

There are many tools for spatial data processing of hydrological model inputs. These tools are not native QGIS commands, most of them come from SAGA GIS and GRASS GIS under the Processing tool. These tools allow you to:

Perform depresionless elevation layers

GRASS GIS: r.fill.dir
SAGA GIS: Fill sinks, Fill sinks (wang & liu), Fill sinks xxl (wang & liu)

Extract stream networks

GRASS GIS: r.stream.extract
SAGA GIS: Channel network

Delimitate basins and channel networks

GRASS GIS: r.basins.fill, r.water.outlet
SAGA GIS: Channel network and drainage basins, Watershed basins

There are more tools for channel order, accumulation maps, watershed analysis and many more.

Complete answers

There are three complete hydrological models in QGIS as far as the author know. Two of them work as GRASS GIS raster tools, and the last as a QGIS plugin.

SIMWE

Overland flow hydrologic simulation using path sampling method (SIMWE) implemented as a GRASS GIS tool named r.sim.water . More information about the software on:

https://grass.osgeo.org/grass64/manuals/r.sim.water.html

TOPMODEL

A physical based hydrological model written in Fortran and then translated to C implemente as a GRASS GIS tool named r.topmodel . More information and tutorials on this link:

https://grass.osgeo.org/grass74/manuals/r.topmodel.html

QSWAT

An implementation of the Soil & Water Assessment Tool (SWAT) in QGIS. The model was developed to quantify the impact of land managenemet in large basins. It combines a hydrological model with a water quality model. It works on HRUs or hidrological response units, a computational unit of area with homogeneous hydrological conditions and land cover. QSWAT is available only on the 32 bit version of QGIS 2.6 as a QGIS plugin.

More information of QSWAT in this link: https://swat.tamu.edu/