Quoted from: https://hydrologicmodels.tamu.edu/bochum-water-balance-model-bwbm/hydrology/
BWBM is a spatially distributed continuous soil moisture accounting and precipitation/snow-melt runoff simulation model. The model is intended for mesoscale (approx. 100-10000 sqkm) watersheds. The model continuously simulates stream flow and all components of the water balance on a spatially distributed basis at a daily time step.
Model is intended for mesoscale (approx. 100-10000 km2 ) watersheds. Model continuously simulates streamflow and all components of the water balance on a spatially distributed basis at a daily time step. Individual components include:
- Precipitation, temperature: inputs are given as spatial fields. A method based on detrended kriging is used to compute the fields from station data.
- Snowmelt: a degree-day method is available, or spatial snow depth and melt fields (e.g., from another model) can be read in.
- Evaporation: three methods are available (FAO, Turc-Wendling, Penman- Monteith).
- Interception: based on leaf area index of vegetation type on each modeling unit.
- Soil moisture: based on a variable capacity bucket concept; capacities are determined from soil porosity and vegetation rooting depth. Due to the daily time step, there is no explicit modeling of infiltration, so all water enters the soil moisture storage.
- Percolation and lateral subsurface flow: based on a nonlinear reservoir concept.
- Groundwater storage: two linear reservoir storages.
- Runoff components: four components (surface, subsurface, and fast and slow groundwater).
- Channel routing: all runoff is assumed to reach a channel within the modeling unit, hence no overland flow routing is done. Channel routing is by either a simple time delay based on the flow distance to the watershed outlet, or a geomorphologic instantaneous unit hydrograph (GIUH) method can be used.