Available Water Balance Items

The .shres file contains a list of all of the simulation output files generated during the WM or WQ simulation. When you use the water balance extraction utility, all of these files are processed and a special set of water balance files are created - the .wblgross files. One file is created for each of the water bal­ance components:

·         Snowmelt and precipitation - projectname_sm.wblgross

·         Canopy interception - projectname_ci.wblgross

·         Ponded surface water - projectname_ol.wblgross

·         Unsaturated zone - projectname_uz.wblgross

·         Saturated zone - projectname_sz.wblgross

The contents of each of these files can be output using the “Detailed” water balances. All of the items in these files are listed and described in the follow­ing tables:

·         Table 6.1 SM - Precipitation and snowmelt items (p. 106)

·         Table 6.2 CI - Canopy interception water balance items (p. 108)

·         Table 6.3 OL - Overland flow items (p. 111) 

·         Table 6.4 UZ - Unsaturated Zone items (p. 115)

·         Table 6.5 SZ - Saturated Zone - all layers (p. 119)

·         Table 6.6 SZ - Saturated Zone - specified by layers (p. 124)

·         Table 6.7 SZ - Saturated Zone - Linear Reservoir all layers (p. 126)

The water balance utility is a very flexible tool that allows you to modify exist­ing Water balance types or create custom Water balance types to suit your needs. The water balance calculations use a water balance Config(uration) file to define Water balance types using the available water balance items and a macro language to control program execution.

To modify existing or custom Water balance types you must understand the available items and what data they contain.

Sign Conventions

MIKE SHE uses a sign convention that is positive in the positive coordinate direction. In other words, water flowing upward in the model is a positive flow in MIKE SHE. Likewise, flow in the direction of increasing x or y is also posi­tive. Boundary flows and other flows that do not have a direction are positive outwards.

However, the water balance utility uses a control volume sign convention, such that all inflows are negative and all outflows are positive. This can cause confusion when calculating a water balance. For example, a vertical down­ward flow through the unsaturated zone will always be a negative result in MIKE SHE. In the water balance control volume, a downward flow into the unsaturated zone will be a positive outflow in the water balance for ponded water, but a negative inflow into the unsaturated zone water balance.

The sign convention for the water balance error of each storage is such that an increasing storage is positive. Thus, a positive water balance error means that the change in storage plus the total outflows is greater than the total inflows. In other words, the error is positive if your model is creating water.