How to manually configure a Water Overlay
When first added to the project, each variant of the water overlay will be created with a default configuration which will allow for an initial calculation to take place and results to display. For most use-cases, it is desirable to add additional data and tweak the settings and parameters of the overlay. This will improve the accuracy and relevancy of the overlay. It is possible to configure the parameters manually, or by using the configuration wizard. A few settings can only be changed manually. Besides the data of geographical features, which have their own means of loading in depending on their type, all manual configuration options are listed here.
Grid cell size configuration
- Main article: Grid overlay
Like all grid overlays, the water overlays have a number of configuration options related to their general method of calculation. Most notably, it is possible to configure the cell size on which the calculations occur.
The grid cell size can be changed by selecting "Change Grid". The minimum and maximum grid cell size depend on the project size. A larger cell size will allow for faster calculations. A smaller cell size will produce more detailed results.
Calculation preference configuration
- Main section: Calculation preference formula
The calculation preference indicates the level of accuracy the calculations should be performed with. Depending on the configuration timesteps will be calculated more conservatively. This affects the time it takes to perform the full calculation, and the exact quantities of water moving between cells.
The calculation preference can be changed by selecting a different setting.
Weather configuration (simulation time, rainfall, evaporation)
- Main section: Weather
The weather configuration, which dictates the duration of the simulation, the amount of rain and the evaporation rate, is modeled as a separate weather object which is connected to the water overlay. The weather object can be replaced with another, changing the main simulation and weather properties. The weather itself can be changed as well.
By selecting the weather object and then switching to the "Simulation" tab, it's possible to change the settings of the weather either for a simple linear setup or with a more complex sequence of values for the duration of the simulation. The complex setup can be created by loading in a CSV (comma separated values) file. By switching to the attributes tab of the weather object, the same properties can be adjusted by directly modifying the attributes.
Ground water configuration
- Main section: Ground water
A ground water GeoTIFF can be loaded in to prepopulate the underground with water in the form of a saturated zone. This is only a relevant configuration when the underground model is active. A ground water GeoTIFF is optional. If no ground water tiff is selected, the assumed ground water level is equal to the WATER_LEVEL of the water area.
The presence of a ground water GeoTIFF can be toggled by checking or unchecking the "Include ground water tiff" checkbox. When checked, a number of GeoTIFFs are available for ground water levels by default. Other GeoTIFFs for groundwater levels can also be loaded in by clicking on "Select GeoTIFF".
Subsidence configuration
- Main section: Subsidence
It's possible to connect the water overlay to a subsidence overlay, if one exists in the project. The result of the subsidence calculation, specifically the amount the terrain has lowered, are applied to the terrain height at the start of the water model's simulation. A connection to a subsidence overlay is optional. If no subsidence overlay is connected, the terrain height is not adjusted in this fashion.
The connection to a subsidence overlay can be made by changing the value selected in the "Subsidence" dropdown to the appropriate subsidence overlay.
Showing system visualization setting
- Main section: System visualization
The water overlay performs a simulation in which much detailed flow takes place, but in which a number of features perform special functions related to water flow. These features include the sewers and the hydrological buildings. The flow of these sections of the hydrological model can be visualized as an explicit graph overlayed on the overlay.
The system visualization can be toggled by checking or unchecking the "Show System Visualization" checkbox.
Active in simulation setting
- Main article: Grid overlay
Like all grid overlays, the water overlays can be configured to either an active or inactive state. This is especially useful when the results of a calculation should be available for insight without the computational overhead of always recalculating the overlay when changes in the project take place.
An overlay can be toggled between active and inactive by checking or unchecking the "Active in simulation" checkbox.
Result type configuration
- Main section: Result type
The water model performs a complete simulation in which water flows through the project area. For many use-cases only a specific type of output resulting from the simulation is relevant. The result type of the water overlay indicates exactly what kind of data is recorded and outputted.
The result type can be changed by selecting the desired result type in the "Result type" dropdown.
Note that via the configuration wizard multiple result types can be added in parallel in the form of result child overlays.
Legend configuration
- Main article: Grid overlay
Depending on the selected result type, the output created by the water overlay can or should be interpreted in different ways. The raw data calculated is assigned colors based on the configured legend. Each result type has an assigned default legend which helps with interpreting the output. The default legends will often be sufficient, but can be modified to fit specific meanings or result ranges.
The legend can be modified in the "Legend" tab by checking the "Has custom legend" checkbox. Entries for the legend can then be added, modified, and removed. Any changes in the legend are applied to the visualization immediately, without recalculation of the overlay's output values.
Keys configuration
- Main section: Keys
The water model's calculations rely on a number of areas and buildings for their input data. Hydrological features and hydrological buildings have special meanings in terms of policy or scenario. To allow for both compatibility with external data as well as parallel calculations for different scenario's, it is possible to (re)define the exact attributes the overlay uses for those inputs. This would allow two instances of a water overlay to work with the same dataset but with different configurations for hydrological features or buildings.
The exact attributes the overlay uses as input from hydrological features and buildings can be changed on the "Keys" tab, by using the relevant dropdown to change the attribute name to the desired attribute.
Keys
The water model makes use of data present in geographical features in the project. This data is used as input for the various calculations which together model the water flow. The water model recognizes what attributes of geographical features form the parameters required for the calculation through key definitions. Each key is the name of an attribute which the water model should use to determine a specific parameter.
Keys are set to default attribute names, which apply to hydrological features, hydrological buildings, and hydrological properties of terrain. Keys can be changed so that imported data can be interpreted without renaming attributes, or to allow different configurations to come forth from the same dataset.
Attributes configuration
- Main section: Attributes
The water model's calculations make use of a number of centralized parameters, which are configured as attributes of the overlay. Depending on the exact variants of the water overlay, some of the parameters will have different defaults to better suit the exact type of calculation. The parameters can be tweaked further to better fit specific use-cases, but in general the defaults are appropriate for most calculations.
Any of the attributes of the overlay can be changed on the "Attributes" tab, by changing the value in the input box for the attribute which is to be changed.