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Output Items

Some of the available output items are calculated as part of another process. For example, the depth of overland water is calculated based on seepage to and from the groundwater and as part of the river model surface water calculations, even if the overland flow is not directly simulated.

Furthermore, some of the output items require that more than one process be simulated. For example, the leaf area index is only available if both evapotranspiration and unsaturated flow are calculated.

In the absence of an explicit remark, the sign convention for MIKE SHE’s output is positive in the positive direction. In other words, all flows in the direction of increasing X, Y and Z coordinates are positive. Thus, vertical downward flows, such as infiltration are negative.

Flows that do not have a direction are positive if storage or outflow is increasing. Thus, all flows leaving the model are positive, and water balance errors are positive if the model is generating water.

Also important to remember is that the output items related to flow are accumulated over the storing time step. In many cases, these values are required for the Water Balance program described in the section Using the Water Balance Tool. The values that are part of the water balance are automatically turned on when the water balance option is selected.

However, the output items that are not flows, such as temperature, water depth and Courant number represent the instantaneous value at the end of the storing time step.

Finally, some of the output items are actually input items. For example, precipitation is usually input as a time series for several polygons or grid code areas. The output file is a fully distributed dfs2 version of the input time series files.

The available output items for gridded data and time series data are listed in Appendix A.1 MIKE SHE Output Items.

Note

The Code listed in the tables in Appendix A.1 MIKE SHE Output Items is the Data Type Code that is needed when importing time series items into the Detailed WM time series output dialogue.

1. Overland flow

The overland flow velocities are discussed in more detail in the section, Output: Overland Flow Velocities.

Overland flow in the x- and y-direction

The overland flow in the x- and y- in the list of available output items is used for the water balance calculations.

The cell velocity cannot be directly calculated from these because the overland water depth is an instantaneous value output at the end of storing time step. Whereas the overland flow in the x- and y- directions are mean-step accumulated over the storing time step. Thus, it is the accumulated flow across the cell face on the positive side of the cell.

You may be tempted to calculate a flow velocity from these values. But you can easily have the situation where the accumulated flow across the boundary is non-zero, but at the end of the storing time step, the water depth is zero. Or, you could have a positive inflow and a zero outflow, which may be misleading when looking at a map of flow velocities.

H Water Depth, P flux and Q flux

The P and Q fluxes are instantaneous fluxes across the positive cell faces of the cells. These are found in a separate _flood.dfs2 results file, along with the H Water Depth. This file is the same format as the MIKE 21 output files generated by MIKE+. Thus, you can use this file to generate flood maps etc. in, for example, the Flood Modelling Toolbox, or the Plot Composer.

You can also add these values to create flow vectors in the Results Viewer.

TS average, TS min, and TS max

Three calculated depths and velocities are available. These are the Average, Minimum and Maximum velocities and depths over the storing timestep.

These values could be useful, for example, when evaluating susceptibility to erosion, or to calculate a flood hazard indicator.

2. Recharge

The data item Total recharge to SZ (positive for downwards flow) is stored on the UZ storing time step interval. It is a Step Accumulated value stored in the results file: _2DUZ_AllCells.dfs2. The calculated Recharge includes the following items:

  • Exchange between UZ and SZ, calculated by the UZ solver.
  • Recharge from Bypass or Macropores if included.
  • Direct flow between SZ and overland (when groundwater table is above ground)
  • Transpiration from SZ (when the roots reach the groundwater)

So, neither baseflow (SZ-M11) nor drain flow is included. These items can be found in the two data items:

  • SZ exchange flow with river (positive when flow from SZ to M11, negative the other way)
  • SZ drainage flow from point (positive drainage, only one way)

The Total recharge to SZ should correspond with the water balance items but note the sign. The easiest way to check this is to look at a Saturated zone water balance, table type:

  • Recharge: exchange between UZ and SZ + Bypass flow or Macropore recharge if included + direct flow between SZ and Overland + transpiration from SZ, all POSITIVE UPWARDS
  • Drain: Drainage flow from point
  • SZ->River: SZ exchange flow with river, positive for flow to the river

Note

The total recharge result type is a flux (i.e. mm/d, mm/h, m/s, etc.) depending on the chosen user unit for Recharge. Whereas the SZ river exchange and Drainage are flows (i.e. m3/s or similar). The Water balance output is in units of Storage depth (mm). That is, it is normalized with the catchment area (using the area inside the outer boundary), or the subcatchment area if a sub-catchment water balance has been extracted.