State Variables in MIKE SHE

The State Variables defined in the MIKE ECO Lab template are passed to MIKE SHE as Species. This is the only way to pass information from MIKE ECO Lab to MIKE SHE.

The Species Name in MIKE SHE must be exactly the same as the State Vari­able Name used in the MIKE ECO Lab Template (except in the case of dual domain mass transfer, which uses the reserved suffix “_2”).

There are four species types in MIKE SHE. Species can be either:

·         Dissolved 
Dissolved species are mobile in the water. They are active in the subsur­face and surface water. Disolved species have a default concentration of [mg/m³].

·         Sorbed 
Sorbed species are only available in the subsurface. They are fixed to the soil matrix and do not move with the water. Sorbed species have a default concentration of [g/g].  

·         Suspended 
Suspended species are only available in ponded water. They do not infil­trate to the UZ or SZ, and they cannot become Sorbed species. If the ponded water infiltrates, the species is left behind. Suspended species have a default concentration of [mg/m³].

·         Fixed 
A fixed species is neither disolved or nor sorbed. It is used as an immo­bile state variable by MIKE ECO Lab. This allows MIKE ECO Lab to read and write arbitrary values to MIKE SHE during the simulation. Fixed spe­cies have an undefined unit.

In particular, the Fixed species is especially interesting in MIKE SHE. It is a species type without pre-defined units of concentration. The non-dimensional species cannot be transported with the flow and can be used as a book-keep­ing mechanism for resulting processes. MIKE ECO Lab itself can read a value from any file, update the value and write it back to the file. However, MIKE ECO Lab cannot append a new value to a file. That is, MIKE ECO Lab cannot read a value, update the value and add the new value as a new time step in file. The Fixed species type gives you a mechanism for handling vari­ous auxiliary user defined quantities during the simulation. In other words, MIKE ECO Lab can read the current Fixed species value, and return a new value to MIKE SHE. MIKE SHE moves forward in time, and MIKE ECO Lab starts over again. In the mean time, MIKE SHE has saved the value from the previous time step. This mechanism greatly increases the flexibility of the MIKE ECO Lab coupling in MIKE SHE. It allows you for example, to create things like ecological indexes that map changing ecohydrologic conditions over time.