Water Module theory

This page acts as a starting point to discover the used theories and technical details behind the Water Module.

The following topics are described:

• Calculation modules
• Theories and formula's
• Computational structure and sequences

Calculation Models

The Water Module performs a large number of calculations to form a complete hydrological simulation. Depending on the desired viewpoint, both the overarching concepts as well as the implemented formulas can be reviewed for detailed insight into how the water overlay works.

Multiple models are implemented which in conjunction form the water model in its entirety.

• Surface model
• Underground model
• Rain model
• Evaporation model
• Sewer model
• Storage model
• Chemical flow model
• Border model

Model connections

To gain insight into how this Water Overlay ties together several models, see Model connections.

Formulas

The precise calculations which govern the water overlay's simulation are many and varied, and based as much as possible on available expert knowledge.

Model related Formula's:

• Timestep formula
• Calculation preference formula
• Surface water level formula
• Groundwater level formula
• Surface flow formula
• Underground flow formula
• Surface evaporation formula
• Underground evaporation formula
• Surface infiltration formula
• Underground infiltration formula

Hydraulic structure related Formula's:

• Culvert formula
• Weir formula
• Breach growth formula
• Breach flow formula
• Pump formula
• Sewer Overflow formula
• Inlet formula

Computational structure and sequences

This section is a stub.

The formulas and concepts come together in a single computational structure which is repeated a large number of times until the total simulation duration has been reached.

Order of operations

During the calculation, multiple facets have to be calculated. In each timestep, each aspect of the calculation has to be performed. Although as timesteps become smaller exact order of operation becomes less important, the order of operations can lead to specific behavioral details in some edge cases.

Calculations are performed in the following order:

• Horizontal surface flow and horizontal underground flow
• Rain
• Building storage
• Sewer inflow
• Surface evaporation
• Groundwater evaporation (saturated zone)
• Groundwater evaporation (unsaturated zone)
• Underground infiltration
• Surface infiltration
• Exfiltration
• Hydrological constructions (culverts, weirs, pumps, in- and outlets, outlets)
• Hydrological areas (sewer overflow, breach in- and outflow)
• Chemical movement, based on the water flow and infiltration which has occurred