Hydromad is an R package (i.e. a software package for the R statistical computing environment). It provides a modelling framework for environmental hydrology: water balance accounting and flow routing in spatially aggregated catchments. It supports simulation, estimation, assessment and visualisation of flow response to time series of rainfall and other drivers.

A minimal unit hydrograph framework is used, where areal rainfall is passed through a soil moisture accounting (SMA) model to estimate effective rainfall; this is then passed through a routing model to estimate streamflow. Included are several implementations of models consistent with this framework, notably the IHACRES CWI and CMD soil moisture accounting models, and unit hydrograph transfer functions for the routing.

The above are cited from: http://hydromad.catchment.org/