Demo Iteration Project

An overview of Demo Iteration.

The Demo Iteration project is available for all users and can be found in the main menu under Edit projects. This project does not count towards your license.

This project is intended for hydrologists and other water experts.

This project showcases the rainfall overlay in a iteration mode.

The demo show the iteration functionality that can be used to adjust the ground infiltration speed using a combo formula.

Calculations using the Iteration option

The demo project simulates a Dutch polder to demonstrate how rainfall infiltration can be modeled using the iteration option.

We want the speed at which rainwater infiltrates to depend on the degree of saturation of the soil. By dividing the rain event into several iteration steps, we can adjust the infiltration rate for each iteration step based on the degree of saturation of the soil. In this way, infiltration can be calculated in a more realistic way.

The purpose of this demo project is to clarify how an iterative calculation can be made. In this case, the infiltration of water during and after a precipitation event was chosen. However, on the basis of this demo project, it should also be possible to calculate other calculations iteratively.

Setup of the Demo Project

The demo project consists of a number of components that are essential for this calculation.

• Combo Overlay
• Rainfall Overlay
• Iteration Collector
• Indicator
• Number of Simulation Iterations

Combo Overlays

Before we create the Rainfall event, a number of overlays are created that serve as input for the various iteration steps. At the end of each iteration the combo overlay is updated an serves as the input for the next iteration step. We'll go through the different combo overlays.

Combo Surface U and Combo Surface V

These overlays say something about the initial velocity of the surface water in x and y directions. When water flows down a slope, we want to use the speed at which the water flows at the end of an iteration step as the initial speed at the next iteration step. The input grid is the result of the last calculation. In the formula of this combo overlay, you can see that the formula is aimed at making sure that it computes with the data from the previous time step, unless the previous iteration step was step 0. In that case, 0 is used.

Make sure to check the box "previous" to make sure the Combo Overlay uses the U and V of the previous itertationstep.
The formula in the combo overlay should in this case read: IF(EQ(ITERATION, 0), 0, A)

Combo Fraction and Combo Groundwater Depth

The purpose of the combo overlay Combo Fraction and the combo Groundwater Depth is to set the input from the previous iteration step to be used, unless the previous iteration step was step 0. In that case, a global value is used. The global DEFAULT_FRACTION is used for the saturation percentage, and the global DEFAULT_TABLE is used for the groundwater level.

The formula in the combo overlay Combo Fraction should in this case read: IF(EQ(ITERATION, 0), GLOBAL_DEFAULT_FRACTION, IF(EQ(A, NO_DATA), GLOBAL_DEFAULT_FRACTION, A))
The formula in the combo overlay Combo Groundwater Depth should in this case read: IF(EQ(ITERATION, 0), GLOBAL_DEFAULT_TABLE, A)

Combo Surface

The combo Surface gives the last value of the waterlevel on the surface and is input for the next iteration step. If there is no previous iteration step, the value should be 0. Make sure to check the box "previous" to make sure the Combo Overlay uses the values of the previous itertationstep.

The formula in the combo overlay Combo Fraction should in this case read: IF(EQ(ITERATION, 0), 0, A)

Combo Infiltration Speed

The purpose of the Combo Overlay Combo Infiltration Speed is to set the correct formula depending on the saturation of the soil. This example uses the overlay Ground BOFEK ID to determine the type of soil.

The formula is entirely hypothetical and only serves to make it clear that, for each iteration step, a value is chosen based on the degree of saturation.

The formula in the combo overlay reads in this case: MAX(0, SUB(GLOBAL_DEFAULT_INFIL, SWITCH(B, 0, 1004, MUL(10, SUB(A, GLOBAL_DEFAULT_FRACTION)), 1006, MUL(5, SUB(A, GLOBAL_DEFAULT_FRACTION)))))

Rainfall Overlay

When setting the rainfall overlay, the default settings can be used. The exceptions are described below.

Rain Event Duration: Here the the total duration of the calculation is specified. Later this is divided into different iterationsteps.
Water System – Water Level: Here the initial water level and the U and V flow are set. Use the option "Advanced: Select Grid Overaly to set initial water level and also flow UV". The water level is set based on a specific overlay, which is the combo overaly Surface. Similarly, the y and x speed from the combo overlay is used as initial input.
Groundwater: Initialize the groundwater level using the Groundwater Depth combo overlay.

Unsaturated Zone: Initialize saturation and storage percentages per grid cell using the Fraction combo overlay.
Generated Output Overlays:

• Surface Last Value
• Rain
• Ground Last Value
• Ground Watertable
• Ground Last Unsaturated Storage
• Ground Last Unsaturated Fraction
• Surface Last U
• Surface Last V
• The number of timeframes is set to 1.

Iteration Collector

The iteration collector is a type of overlay. It shows the results of each iteration step. An iteration collector needs an input overlay, in this case it is the Rain event. Of each itteration step a certain amount of timeframes can be saved. This is sed in the modulus, which can be found in the attributes of the iteration Collector. By default, this is set to 1. This means that only one (the last) result of each iteration step is saved and used as a timeframe in the iteration collector.

Indicator

Het doel van de indicator is het instellen van de start en eind tijd van de iteratiestap van de regenwateroverlay. Om dit te bewerkstelligen worden een aantal queries uitgevoerd . Allereerst wordt bepaald hoeveel iteratiestappen zijn gekozen en hoe lang de totale simulatietijd is ingesteld. Dit gebeurd met de query SELECT_ITERATIONS_WHERE en SELECT_ATTRIBUUT_WHERE_NAME_IS_RAIN_M_AND_OVERLAY_IS_10_AND_RELATION_IS_WEATHER_AND_INDEX_IS_2.

Met de querys UPDATE_OVERLAY_PARTIAL_START_SEC_WHERE_OVERLAY_IS_3 en UPDATE_OVERLAY_PARTIAL_END_SEC_WHERE_OVERLAY_IS_3 worden respectievelijk de begin en eindtijd van de volgende iteratiestap bijgesteld. Om te weten wat de volgende iteratiestap is wordt de query SELECT_ITERATION_WHERE uitgevoerd.

Fraction Start en Fraction End geven de start en end als fractie. Bij Start en End wordt dit uitgedrukt in seconden door deze fractie te vermenigvuldigen met de totale simulatietijd.

Number of Iterations

Set through the interface (default is 1).

Notes and Limitations

Debugging cannot be downloaded per iteration but can be saved for each iteration. Specific updates (e.g., updating attributes for certain building types in iteration 5) can be executed using the API and indicator but not through TQL for non-initial iterations.

Exploring the project

To begin exploring the project, see the outlet located on the left side.

See also

• List of Demo Projects