iMOD User Manual version 5.2 (html)

12.1CAP MetaSWAP Unsaturated zone module

The process of groundwater recharge and discharge through the unsaturated zone is simulated in iMODFLOW with the MetaSWAP concept (see Annex 1). MetaSWAP is developed by Alterra, Wageningen as part of the SIMGRO model code [Van Walsum(2017b)], [Van Walsum(2017a)]. The SIMGRO framework is intended for regions with an undulating topography and unconsolidated sediments in the (shallow) subsoil. Both shallow and deep groundwater levels can be modelled by MetaSWAP. This model is based on a simplification of ‘straight Richards’, meaning that no special processes like hysteresis, preferential flow and bypass flow are modelled. Snow is not modelled, and neither the influence of frost on the soil water conductivity. A perched watertable can be present in the SVAT column model, but interflow is not modelled. There are plans for including the mentioned special processes in MetaSWAP Inundation water can be modelled as belonging to both groundwater and surface water at the same time. Processes that are typical for steep slopes are not included. The code contains several parameterized water management schemes, including irrigation and water level management.
The input data required for MetaSWAP are [Van Walsum et al.(2016)]:

• BND: Boundary setting, used to specify active MetaSWAP elements

• LGN: Landuse code, should be referred to by the file luse_mswp.inp

• RTZ: Rootzone thickness in cm (min. value is 10 centimeter).

• SFU: Soil Fysical Unit should be referred to by fact_mswp.inp.

• MET: Meteo Station number, should be referred to by mete_mswp.inp.

• SEV: Surface Elevation (m+MSL).

• ART: Artificial Recharge Type, 0=no occurrence, ART$>$0 means present at current location whereby ART=1: from groundwater, ART=2: from surface water extraction

• ARL: Artificial Recharge Location, number of modellayer from which water is extracted.

• ARC: Artificial Recharge Capacity (mm/d).

• WA: Wetted Area (m${}^{2}$) specifies the total area occupied by surface water elements. Value will be truncated by maximum cellsize.

• UA: Urban Area (m${}^{2}$) specifies the total area occupied by urban area. Value will be truncated by maximum cellsize.

• PD: Ponding Depth (m)

• PWT: Depth of the perched water table level (m-SL)