Mass Balance

Theoretically, the applied computational scheme should ensure mass conservation in every case. In practical applications, the mass balance may be jeopardised in a number of situations, such as:

• Relatively sharp changes of storage width due to rapid changes of water depth or a sharp change of cross section shape with depth. This may be e.g. the case at relatively small depths in circular pipes and in cross sections with flow bank zones.
• Sharp changes in surface area of basins
• Surcharge of manholes

The scale of the problem is usually related to the length of the simulation time step.