How to initialize a groundwater prequel
When working with the complete groundwater model of the Water Overlay, it is very likely that any initial configuration for groundwater is not actually the state of the groundwater "at rest", meaning that during the initial period of the simulation the groundwater will always flow to a different location into a more stable configuration. For example, an initial groundwater dataset may have a consistent groundwater level defined for a large plot of land, while the more natural situation may be that the water follows a curve due to the way water flows into and out of the ground.
The consequence of this phenomenon, especially for short simulations, is that groundwater will not yet have reached a natural state by the the time the main event of the simulation takes place, or even when the simulation ends. To compensate for this, it is possible to prepare the groundwater data by setting up and running a stationary calculation for groundwater, allowing it to settle, and using the (more natural and stable) result as the initial groundwater state for the actual calculation.
This can also be achieved in a dynamic setup in which the calculation for intialization is set up as a "prequel", an explicit precursor calculation to the actual simulation.
- Add a Groundwater Overlay intended to initialize a groundwater level, ahead of the actual intended simulation.
- Ensure that the Groundwater Overlay has the groundwater mode set to "Complete".
- Ensure that the Groundwater Overlay has data for groundwater set, if one is available.
- Ensure that the Groundwater Overlay has a ground last value output.
- Configure the rainfall for the model to run stationary, for a period of multiple weeks.
- Recalculate the Groundwater Overlay.
- Add a second Groundwater Overlay, which will use the first Groundwater Overlay's results as input.
- Open the second Groundwater Overlay's Water Overlay configuration wizard, and proceed to the groundwater step.
- Select the option "Select a Groundwater Depth Grid Overlay".
- Select the first Ground Water Overlay as prequel.