CatchmentUHMMaxNumberOfCells Property |
Maximum number of cells in hydrograph routing. To disable maximum, set to zero. A sound value
is 200-400.
If the maximum is enforced, the advanced routing method will be used. The advanced routing is a higher order advection scheme, AdvectiveTransport.
The advanced routing/advection scheme is computationally somewhat more expensive than the simple routing, so the number of advanced routing cells will be half of MaxNumberOfCells.
Namespace: DHI.Mike1D.RainfallRunoffModule
Assembly: DHI.Mike1D.RainfallRunoffModule (in DHI.Mike1D.RainfallRunoffModule.dll) Version: 19.0.0.0 (11.1.1.1111)
SyntaxRemarks
When lagtime is large, (LagTime or Length, depending on LagTimeType),
the number of computational cells can also be very large. UHM is used for catchments of size from a few km2 to 10000 km2
and even larger. The length can be up to several hundred kilometers and lagtimes in the order of days. Assuming a
lagtime of, say 10 days, that can give a hydrograph time of 30 days, and with a time step of 1 minute, that
will produce more than 40000 computational cells, which are evaluated in each time step. This has a performance impact
both in terms of computation time and memory consumption.
In general, for fair accuracy using the UHM model, no more than a hundred computational cells are required.
There are two approaches for limiting the number of computational cells:
- Increase the time step. In case of a lagtime of 10 days, timestep of one or two hours could be applied. This is computationally very efficient. The downside is that the loss is very rudimentary modelled, and may result in larger losses than desired. E.g. a short, intense rain over one minute, used in a two hour time step may be completely absorbed by losses.
- Create less cells, and apply the advanced routing between the cells.
See Also