Evapotranspiration model (Water Overlay) - Revision history

Frank@tygron.nl at 11:41, 14 July 2026

2026-07-14T11:41:24Z

← Older revision		Revision as of 11:41, 14 July 2026
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	* The next time key should always be larger than the previous time key.		* The next time key should always be larger than the previous time key.
	* If the next time key for the evaporation rate is smaller than the previous time key for [[rain model (Water Overlay)\|rainfall]], the previous rate of evaporation is continued until the end of the simulation.		* If the next time key for the evaporation rate is smaller than the previous time key for [[rain model (Water Overlay)\|rainfall]], the previous rate of evaporation is continued until the end of the simulation.
	\|api=*[[Api session event ~~editoroverlay~~ set water weather]]		\|api=*[[Api session event editor overlay set water weather]]
	}}		}}

	{{WaterOverlay formula nav}}		{{WaterOverlay formula nav}}

Frank@tygron.nl at 11:40, 14 July 2026

2026-07-14T11:40:57Z

← Older revision		Revision as of 11:40, 14 July 2026
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	* The next time key should always be larger than the previous time key.		* The next time key should always be larger than the previous time key.
	* If the next time key for the evaporation rate is smaller than the previous time key for [[rain model (Water Overlay)\|rainfall]], the previous rate of evaporation is continued until the end of the simulation.		* If the next time key for the evaporation rate is smaller than the previous time key for [[rain model (Water Overlay)\|rainfall]], the previous rate of evaporation is continued until the end of the simulation.
	\|api=*[[Api ~~editor~~ session event editoroverlay set water weather]]		\|api=*[[Api session event editoroverlay set water weather]]
	}}		}}

	{{WaterOverlay formula nav}}		{{WaterOverlay formula nav}}

Frank@tygron.nl at 11:40, 14 July 2026

2026-07-14T11:40:45Z

← Older revision		Revision as of 11:40, 14 July 2026
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	* The next time key should always be larger than the previous time key.		* The next time key should always be larger than the previous time key.
	* If the next time key for the evaporation rate is smaller than the previous time key for [[rain model (Water Overlay)\|rainfall]], the previous rate of evaporation is continued until the end of the simulation.		* If the next time key for the evaporation rate is smaller than the previous time key for [[rain model (Water Overlay)\|rainfall]], the previous rate of evaporation is continued until the end of the simulation.
	\|api=*[[Api editor session event ~~editor overlay~~ set water weather]]		\|api=*[[Api editor session event editoroverlay set water weather]]
	}}		}}

	{{WaterOverlay formula nav}}		{{WaterOverlay formula nav}}

Frank@tygron.nl: /* Example for dynamic evaporation */

2026-07-14T11:40:27Z

Example for dynamic evaporation

← Older revision		Revision as of 11:40, 14 July 2026
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	* The next time key should always be larger than the previous time key.		* The next time key should always be larger than the previous time key.
	* If the next time key for the evaporation rate is smaller than the previous time key for [[rain model (Water Overlay)\|rainfall]], the previous rate of evaporation is continued until the end of the simulation.		* If the next time key for the evaporation rate is smaller than the previous time key for [[rain model (Water Overlay)\|rainfall]], the previous rate of evaporation is continued until the end of the simulation.
	\|api=*[[~~Editor~~ session event editor overlay set water weather]]		\|api=*[[Api editor session event editor overlay set water weather]]
	}}		}}

	{{WaterOverlay formula nav}}		{{WaterOverlay formula nav}}

Frank@tygron.nl at 11:40, 14 July 2026

2026-07-14T11:40:15Z

Frank@tygron.nl at 11:12, 8 July 2026

2026-07-08T11:12:41Z

← Older revision		Revision as of 11:12, 8 July 2026
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	~~The~~ combined ~~processes through which~~ water ~~is transferred~~ to the atmosphere from open water and vegetation ~~that make up the surface cells~~. Two types of are implemented:		Evapotranspiration is the combined process of water transferring to the atmosphere from open water and vegetation. Two types are implemented:

	* [[#Surface Evaporation\|Evaporation]]: the movement of water directly to the air from sources such as the soil and water bodies. It can be affected by factors including heat, humidity, solar radiation and wind speed.		* [[#Surface Evaporation\|Evaporation]]: the movement of water directly to the air from sources such as the soil and water bodies. It can be affected by factors including heat, humidity, solar radiation and wind speed.
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	=== Feddes factor ===		=== Feddes factor ===
	Conceptually, water can transpirate from the ground via crop, tree and plant foliage. Their roots can draw water from the unsaturated and saturated zones in the ground, when these reach deep enough and the [[Water transpiration factor (Water Overlay)\|transpiration factor]] is non-zero. Water is drawn from the ground and transpirated into the air, effectively removing it from the hydrological model.		Conceptually, water can transpirate from the ground via crop, tree and plant foliage. Their roots can draw water from the unsaturated and saturated zones in the ground, when these reach deep enough and the [[Water transpiration factor (Water Overlay)\|transpiration factor]] is non-zero. Water is drawn from the ground and transpirated into the air, effectively removing it from the hydrological model.
	Water for transpiration can only be drawn from sections of the ground which are within reach of the roots, as defined by the root depth. Using the multiple root depth values, it is also possible to define a threshold at which the roots are unable, or less able, to extract ground water, due to oxygen stress. It such ~~case~~ up to 4 root depth values ~~have to~~ be provided, from deepest to ~~less deep~~.		Water for transpiration can only be drawn from sections of the ground which are within reach of the roots, as defined by the root depth. Using the multiple root depth values, it is also possible to define a threshold at which the roots are unable, or less able, to extract ground water, due to oxygen stress. In such cases, up to four root depth values must be provided, ordered from deepest to shallowest.

	[[File:Feddes_trapezium.jpg\|500px]]		[[File:Feddes_trapezium.jpg\|500px]]
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	Similar to the [[#Surface evaporation\|surface evaporation]], the rate of ground transpiration is also determined by the [[Weather (Water Overlay)\|weather definition]]'s [[Evaporation m (Water Overlay)\|evaporation rate]]. Multiplying the weather's evaporation rate and the transpiration factor of the building or terrain (as applicable) gives the actual transpiration rate for the ground.		Similar to the [[#Surface evaporation\|surface evaporation]], the rate of ground transpiration is also determined by the [[Weather (Water Overlay)\|weather definition]]'s [[Evaporation m (Water Overlay)\|evaporation rate]]. Multiplying the weather's evaporation rate and the transpiration factor of the building or terrain (as applicable) gives the actual transpiration rate for the ground.

	Ground transpiration first draws water from the unsaturated region and then from the saturated region. If, according to the calculated transpiration rate, a sufficient amount of water can transpirate from the unsaturated zone, no water will transpirate from the saturated zone. Otherwise, ~~all~~ water in the unsaturated zone ~~which~~ is ~~in reach of the roots of the building or terrain (as applicable) is transpirated~~, ~~and the remainder of the amount of water which should transpirate according to the transpiration rate is transpirated~~ from the saturated zone. The sum of transpiration in the unsaturated zone and the saturated zone will never exceed the calculated transpiration rate.		Ground transpiration first draws water from the unsaturated region and then from the saturated region. If, according to the calculated transpiration rate, a sufficient amount of water can transpirate from the unsaturated zone, no water will transpirate from the saturated zone. Otherwise, available water in the unsaturated zone is transpired first, with any remaining requirement drawn from the saturated zone. The sum of transpiration in the unsaturated zone and the saturated zone will never exceed the calculated transpiration rate.

	==Example for dynamic evaporation==		==Example for dynamic evaporation==
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	In total it can be expected that 1,5 * ( (35-0) / (2460) ) + 1,9 ( (42-35) / (2460) ) + 0,5 ( (120-42) / (24*60) ) = 0.036 + 0.009 + 0.027 = 0,0728 mm of water will have evaporated in a total simulation time of 120 minutes.		In total it can be expected that 1,5 * ( (35-0) / (2460) ) + 1,9 ( (42-35) / (2460) ) + 0,5 ( (120-42) / (24*60) ) = 0.036 + 0.009 + 0.027 = 0,0728 mm of water will have evaporated in a total simulation time of 120 minutes.

	If~~, during any timestep, the amount of~~ water ~~present~~ is less than ~~what is~~ calculated ~~to evaporate~~, the water ~~present will evaporate, but because there was not enough water to evaporate, the actual total amount of evaporation will be less than the amount that was calculated to potentially evaporate~~.		If available water is less than the calculated evaporation amount for a timestep, only the available water evaporates.

	{{article end		{{article end

Frank@tygron.nl at 10:48, 16 December 2025

2025-12-16T10:48:05Z

← Older revision		Revision as of 10:48, 16 December 2025
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	{{article end		{{article end
	\|seealso=		\|seealso=
			<div style="column-count:2">
	* [[Ground transpiration result type (Water Overlay)]]		* [[Ground transpiration result type (Water Overlay)]]
	* [[Surface evaporation result type (Water Overlay)]]		* [[Surface evaporation result type (Water Overlay)]]
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	* [[Surface last evaporation result type (Water Overlay)]]		* [[Surface last evaporation result type (Water Overlay)]]
	* [[Last evapotranspiration result type (Water Overlay)]]		* [[Last evapotranspiration result type (Water Overlay)]]
			</div>
	==Related formulas==		==Related formulas==
	* [[Surface evaporation formula (Water Overlay)\|Surface evaporation formula]]		* [[Surface evaporation formula (Water Overlay)\|Surface evaporation formula]]

Frank@tygron.nl at 10:46, 16 December 2025

2025-12-16T10:46:48Z

← Older revision		Revision as of 10:46, 16 December 2025
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	* [[Surface evaporation result type (Water Overlay)]]		* [[Surface evaporation result type (Water Overlay)]]
	* [[Evapotranspiration result type (Water Overlay)]]		* [[Evapotranspiration result type (Water Overlay)]]
			* [[Ground last transpiration result type (Water Overlay)]]
			* [[Surface last evaporation result type (Water Overlay)]]
			* [[Last evapotranspiration result type (Water Overlay)]]
	==Related formulas==		==Related formulas==
	* [[Surface evaporation formula (Water Overlay)\|Surface evaporation formula]]		* [[Surface evaporation formula (Water Overlay)\|Surface evaporation formula]]

Frank@tygron.nl at 10:46, 16 December 2025

2025-12-16T10:46:12Z

← Older revision		Revision as of 10:46, 16 December 2025
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	If, during any timestep, the amount of water present is less than what is calculated to evaporate, the water present will evaporate, but because there was not enough water to evaporate, the actual total amount of evaporation will be less than the amount that was calculated to potentially evaporate.		If, during any timestep, the amount of water present is less than what is calculated to evaporate, the water present will evaporate, but because there was not enough water to evaporate, the actual total amount of evaporation will be less than the amount that was calculated to potentially evaporate.

			{{article end
			\|seealso=
			* [[Ground transpiration result type (Water Overlay)]]
			* [[Surface evaporation result type (Water Overlay)]]
			* [[Evapotranspiration result type (Water Overlay)]]
	==Related formulas==		==Related formulas==
	* [[Surface evaporation formula (Water Overlay)\|Surface evaporation formula]]		* [[Surface evaporation formula (Water Overlay)\|Surface evaporation formula]]
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	* [[Ground model (Water Overlay)\|Ground model]]		* [[Ground model (Water Overlay)\|Ground model]]

	~~{{article end~~
	~~\|seealso=~~
	* [[Ground transpiration result type (Water Overlay)]]
	* [[Surface evaporation result type (Water Overlay)]]
	* [[Evapotranspiration result type (Water Overlay)]]
	\|notes=		\|notes=
	* The [[Water Overlay Wizard\|configuration wizard]] is the easiest way to adjust evaporation and rainfall.		* The [[Water Overlay Wizard\|configuration wizard]] is the easiest way to adjust evaporation and rainfall.

Frank@tygron.nl at 10:45, 16 December 2025

2025-12-16T10:45:41Z

@@ Line 66: / Line 66: @@
 If, during any timestep, the amount of water present is less than what is calculated to evaporate, the water present will evaporate, but because there was not enough water to evaporate, the actual total amount of evaporation will be less than the amount that was calculated to potentially evaporate.
 {{article end
@@ Line 83: / Line 91: @@
 * If the next time key for the evaporation rate is smaller than the previous time key for [[rain model (Water Overlay)|rainfall]], the previous rate of evaporation is continued until the end of the simulation.
 }}
 {{WaterOverlay formula nav}}

← Older revision		Revision as of 11:40, 14 July 2026
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	The general evaporation amount per period is converted to an amount per second.		The general evaporation amount per period is converted to an amount per second.

	In case less water is present at a particular grid cell, the amount of evaporation will be less than the maximum possible evaporation at the time in the simulation. The remainder will not be carried over to the next time step and will ~~therefor~~ always be discarded.		In case less water is present at a particular grid cell, the amount of evaporation will be less than the maximum possible evaporation at the time in the simulation. The remainder will not be carried over to the next time step and will therefore always be discarded.

	The default setup for evaporation consists of a single period of evaporation and an evaporation amount. It is possible to configure an evaporation rate which [[How_to_load_in_dynamic_evaporation_rate_(Water_Overlay)\|varies over time]]. More periods with varying amounts of evaporation (including an evaporation rate of zero) can be defined.		The default setup for evaporation consists of a single period of evaporation and an evaporation amount. It is possible to configure an evaporation rate which [[How_to_load_in_dynamic_evaporation_rate_(Water_Overlay)\|varies over time]]. More periods with varying amounts of evaporation (including an evaporation rate of zero) can be defined.
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	=== Feddes factor ===		=== Feddes factor ===
	Conceptually, water can transpirate from the ground via crop, tree and plant foliage. Their roots can draw water from the unsaturated and saturated zones in the ground, when these reach deep enough and the [[Water transpiration factor (Water Overlay)\|transpiration factor]] is non-zero. Water is drawn from the ground and ~~transpirated~~ into the air, effectively removing it from the hydrological model.		Conceptually, water can transpirate from the ground via crop, tree and plant foliage. Their roots can draw water from the unsaturated and saturated zones in the ground, when these reach deep enough and the [[Water transpiration factor (Water Overlay)\|transpiration factor]] is non-zero. Water is drawn from the ground and transpired into the air, effectively removing it from the hydrological model.
	Water for transpiration can only be drawn from sections of the ground which are within reach of the roots, as defined by the root depth. Using the multiple root depth values, it is also possible to define a threshold at which the roots are unable, or less able, to extract ground water, due to oxygen stress. In such cases, up to four root depth values must be provided, ordered from deepest to shallowest.		Water for transpiration can only be drawn from sections of the ground which are within reach of the roots, as defined by the root depth. Using the multiple root depth values, it is also possible to define a threshold at which the roots are unable, or less able, to extract ground water, due to oxygen stress. In such cases, up to four root depth values must be provided, ordered from deepest to shallowest.

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	=== Seasonal factor ===		=== Seasonal factor ===
	[[File:Seasonal_evap_grass.jpg\|thumb\|right\|Varying [[Water evaporation factor (Water Overlay)\|evaporation factor]] of grass, depending on the [[Season formula (Water Overlay)\|time of year]].]]		[[File:Seasonal_evap_grass.jpg\|thumb\|right\|Varying [[Water evaporation factor (Water Overlay)\|evaporation factor]] of grass, depending on the [[Season formula (Water Overlay)\|time of year]].]]
	The ground evaporation can be configured directly by changing the terrain type's [[terrain water transpiration factor (Water Overlay)\|WATER_TRANSPIRATION_FACTOR]] and building 's [[Water evaporation factor (Water Overlay)\|WATER_TRANSPIRATION_FACTOR]]. If these attributes are set to 0, no ground evaporation will take place. This attribute can also be set as 4 distinct values, one for each [[Season formula (Water Overlay)\|growth season]]. This allows for more transpiration during a crops growth season and less during the winter.		The ground evaporation can be configured directly by changing the terrain type's [[terrain water transpiration factor (Water Overlay)\|WATER_TRANSPIRATION_FACTOR]] and building's [[Water evaporation factor (Water Overlay)\|WATER_TRANSPIRATION_FACTOR]]. If these attributes are set to 0, no ground evaporation will take place. This attribute can also be set as 4 distinct values, one for each [[Season formula (Water Overlay)\|growth season]]. This allows for more transpiration during a crops growth season and less during the winter.

	=== Varying transpiration rate===		=== Varying transpiration rate===
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	\|-		\|-
	\|35		\|35
	\|1,5		\|1.5
	\|-		\|-
	\|42		\|42
	\|1,9		\|1.9
	\|-		\|-
	\|120		\|120
	\|0,5		\|0.5
	\|}		\|}
	For the sake of simplicity, we will assume a [[Surface water evaporation factor model attribute (Water Overlay)\|surface water evaporation factor]] of 1. We will also assume that there is sufficient water to evaporate.		For the sake of simplicity, we will assume a [[Surface water evaporation factor model attribute (Water Overlay)\|surface water evaporation factor]] of 1. We will also assume that there is sufficient water to evaporate.

	This format can be interpreted as follows:		This format can be interpreted as follows:
	* The first period is starts at t=0 minutes and ends at t=35 minutes. In this first period, water will evaporate at a rate of 1,5 mm per day. Uniformly this gives 1,5 / (24 * 60 * 60) = 0.000017 mm per second.		* The first period starts at t=0 minutes and ends at t=35 minutes. In this first period, water will evaporate at a rate of 1.5 mm per day. Uniformly this gives 1.5 / (24 * 60 * 60) = 0.000017 mm per second.
	* The second period starts at t=35 minutes and ends at t=42 minutes. In this period, water will evaporate at a rate of 19 mm per day. Uniformly this is 1,9 / (24 * 60 * 60) = 0.000022 mm per second.		* The second period starts at t=35 minutes and ends at t=42 minutes. In this period, water will evaporate at a rate of 19 mm per day. Uniformly this is 1.9 / (24 * 60 * 60) = 0.000022 mm per second.
	* The last period starts at t=42 minutes and ends at t=120 minutes. In this period, water will evaporate at a rate of 5 mm per day. Uniformly this is 0,5 / (24 * 60 * 60) = 0,000006 mm per second.		* The last period starts at t=42 minutes and ends at t=120 minutes. In this period, water will evaporate at a rate of 5 mm per day. Uniformly this is 0.5 / (24 * 60 * 60) = 0.000006 mm per second.
	In total it can be expected that 1,5 * ( (35-0) / (2460) ) + 1,9 ( (42-35) / (2460) ) + 0,5 ( (120-42) / (24*60) ) = 0.036 + 0.009 + 0.027 = 0,0728 mm of water will have evaporated in a total simulation time of 120 minutes.		In total it can be expected that 1.5 * ( (35-0) / (2460) ) + 1.9 ( (42-35) / (2460) ) + 0.5 ( (120-42) / (24*60) ) = 0.036 + 0.009 + 0.027 = 0.0728 mm of water will have evaporated in a total simulation time of 120 minutes.

	If available water is less than the calculated evaporation amount for a timestep, only the available water evaporates.		If available water is less than the calculated evaporation amount for a timestep, only the available water evaporates.
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	* The next time key should always be larger than the previous time key.		* The next time key should always be larger than the previous time key.
	* If the next time key for the evaporation rate is smaller than the previous time key for [[rain model (Water Overlay)\|rainfall]], the previous rate of evaporation is continued until the end of the simulation.		* If the next time key for the evaporation rate is smaller than the previous time key for [[rain model (Water Overlay)\|rainfall]], the previous rate of evaporation is continued until the end of the simulation.
			\|api=*[[Editor session event editor overlay set water weather]]
	}}		}}

	{{WaterOverlay formula nav}}		{{WaterOverlay formula nav}}