View source for Calculate stable water level use case (Water Overlay)

For water management purposes it can be relevant to know how water will stabilize throughout the system. This can be in a default situation, where there is a nominal amount of water in- and outflow. This can also be in a situation where the system is under duress, such as with a consistent amount of rainfall. There are multiple possible definitions of a stable water system, but a common characteristic is that the inflow and outflow match up, leading to either a consistent amount of water in the system or a predictable water rise/fall at points of measurement.

For the purposes of this scenario, a simple hydrological model will be assumed, with an inflow of water from an upstream source and a downstream means for water to leave the water system.

==Requirements==
Before implementing this use-case, make sure you have a [[Basic water model use case (Water Overlay)|basic water model]] set up. For the specified scenario, the [[Rainfall_(Overlay)|rainfall overlay]] is recommended, although any variant will work.

Also ensure the following in your project, if possible:
* The hydrological system has appropriate inflows and outflows.
* The hydrological system has a [[Surface last value result type (Water Overlay)|SURFACE_LAST_VALUE]] result type, either as main result or as a [[Result type (Water Overlay)#Multiple result child overlays|child result type]].
* The simulation is set up to output a reasonable amount of timeframes. For a stabilization case, one timeframe per 12 hours of simulation time is reasonable.

==Steps==
The use-case can be implemented through the following steps.
{{Editor steps|title=determine stable water levels
|Configure a [[Basic water model use case (Water Overlay)|base hydrological system]].
|Ensure the overlay is (re)calculated.
|Inspect the "Surface last value" result overlay.
|In the location where water should stabilize, place a point measurement using the [[measurement tool]].
|If the line in the graph becomes horizontal, that's the time and level at which the water is stable.
}}

{{article end
|notes=
* A possibility for water to stabilize is most likely if the water inflow is constant, but the outflow increases as water in the system increases. A [[weir (Water Overlay)| Weir]] at the outflow side of the water system can effectuate this.
* It's possible that the water does not stabilize, if the water flows in faster than water can leave the water system.
* It's possible that the water in the water system is effectively exhausted before stability is reached, if water flows out faster than water enters the system.
}}

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