# wflow_sbm

Wflow_sbm represents a family of hydrological models derived from the CQflow model (Köhler et al.,2006) that has been applied in various countries, most notably in Central America. The models have the vertical SBM concept in common. The soil part of wflow_sbm is largely based on the Topog_SBM model but has had considerable changes over time. Topog_SBM is specifically designed to simulate fast runoff processes in small catchments while wflow_sbm model can be applied more widely. The main differences are for the vertical concept SBM of wflow_sbm:

• The unsaturated zone can be split-up in different layers
• The addition of evapotranspiration losses
• The addition of a capillary rise

The vertical SBM concept is explained in more detail in the following section SBM vertical concept.

Topog_SBM uses an element network based on contour lines and trajectories for water routing. Wflow_sbm models differ in how the lateral components:

• river
• land
• subsurface

are solved.

## SBM + Kinematic wave

For the lateral components of this wflow_sbm model water is routed over a D8 network, and the kinematic wave approach is used for river, overland and lateral subsurface flow. This is described in more detail in the section Kinematic wave.

Overview of the different processes and fluxes in the wflow_sbm model:

Below the mapping for this wflow_sbm model (type sbm) to the vertical SBM concept (instance of struct SBM) and the different lateral concepts is presented. For an explanation about the type parameters between curly braces after the struct name see Vertical and lateral models.

vertical => struct SBM{T,N,M}
lateral.subsurface => struct LateralSSF{T}
lateral.land => struct SurfaceFlow{T,R,L}
lateral.river => struct SurfaceFlow{T,R,L}
lateral.river.lake => struct NaturalLake{T} # optional
lateral.river.reservoir => struct SimpleReservoir{T} # optional

## SBM + Groundwater flow

For river and overland flow the kinematic wave approach over a D8 network is used for this wflow_sbm model. For the subsurface domain, an unconfined aquifer with groundwater flow in four directions (adjacent cells) is used. This is described in more detail in the section Groundwater flow.

Below the mapping for this wflow_sbm model (type sbm_gwf) to the vertical SBM concept (instance of struct SBM) and the different lateral concepts. For an explanation about the type parameters between curly braces after the struct name see Vertical and lateral models.

vertical => struct SBM{T,N,M}
lateral.subsurface.flow => struct GroundwaterFlow{A, B}
lateral.subsurface.recharge => struct Recharge{T} <: AquiferBoundaryCondition
lateral.subsurface.river => struct River{T} <: AquiferBoundaryCondition
lateral.subsurface.drain => struct Drainage{T} <: AquiferBoundaryCondition # optional
lateral.land => struct SurfaceFlow{T,R,L}
lateral.river => struct SurfaceFlow{T,R,L}
lateral.river.lake => struct NaturalLake{T} # optional
lateral.river.reservoir => struct SimpleReservoir{T} # optional

## References

• Köhler, L., Mulligan, M., Schellekens, J., Schmid, S., Tobón, C., 2006, Hydrological impacts of converting tropical montane cloud forest to pasture, with initial reference to northern Costa Rica. Final Technical Report DFID‐FRP Project No. R799.