Once you have selected your processes, then there are several simulation parameters that need to be defined. None of these are initially critical and the default values are generally satisfactory initially. You can come back to all of these at any time.
However, we recommend that you set up you simulation period when you first create your model. The simulation period is used to verify all of you time series data to make sure that your time series cover your simulation period. You can still add your time series files, but if your simulation period is not correct, then you will get a warning message in the message field at the bottom of the page and the time series graphs will not display the proper portion of the time series.
In MIKE SHE, all of the simulation input and output is in terms of real dates, which makes it easy to coordinate the input data (e.g. pumping rates), the simulation results (e.g. calculated heads) and field observations (e.g. measured water levels).
The default solver parameters for each of the processes are normally reasonable and there is usually no reason to change these unless you have a problem with convergence or if the simulation is taking too long to run. For more information on the solver parameters, you should see the individual help sections for the different solvers:
· OL Computational Control Parameters (V1 p. 191)
· UZ Computational Control Parameters (V1 p. 196)
· SZ Computational Control Parameters (V1 p. 197)
Likewise, the time step control is important, but the default values are usually reasonable to get your model up and running. Then, you should go back to the Time Step Control (V1 p. 186) dialogue to optimize your simulation time stepping. For more information on time step control, you can see the Controlling the Time Steps (V1 p. 81) section.
Note: Although the different hydrologic processes can run on different time steps, the processes exchange water explicitly. There are restrictions on the relationship between the time steps in the processes. In particular, the longer time steps must be even multiples of the shorter time steps. In other words, a 24 hour groundwater time step can included four 6-hour unsaturated flow time steps, which can each include three 2-hour overland flow time steps. See Time Step Control (V1 p. 186) for more information.
