Green-Ampt Infiltration Parameters - Revision history

Anne.Kolega: /* Capillary Suction Head */ delete a for grammar

2026-02-26T02:04:28Z

Capillary Suction Head: delete a for grammar

← Older revision		Revision as of 12:04, 26 February 2026
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	'''Figure 3: Sensitivity of cumulative infiltration in the Plynlimon Gwy catchment to the Capillary Suction Head parameter in the Green-Ampt infiltration model.'''<br>		'''Figure 3: Sensitivity of cumulative infiltration in the Plynlimon Gwy catchment to the Capillary Suction Head parameter in the Green-Ampt infiltration model.'''<br>
	<br>		<br>
	As a consequence of this, there is a less runoff generated as shown in Figure 4. As can be seen, the model is not particularly sensitive to the suction head parameter and this fits with observations made within the literature from other similar studies.<br>		As a consequence of this, there is less runoff generated as shown in Figure 4. As can be seen, the model is not particularly sensitive to the suction head parameter and this fits with observations made within the literature from other similar studies.<br>
	<br>		<br>

Anne.Kolega: /* Saturated Hydraulic Conductivity */ changed figure 7 to Figure 7

2026-02-26T01:57:54Z

Saturated Hydraulic Conductivity: changed figure 7 to Figure 7

← Older revision		Revision as of 11:57, 26 February 2026
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	=== Porosity ===		=== Porosity ===
	The porosity value represents the volume of dry voids per volume of soil and provides the maximum moisture deficit that is available, the difference between the moisture content at saturation and at the start of the simulation. Sandy soils tend to have lower porosities than clay soils, but drain to lower moisture contents between rainfall events because water is not held as strongly in the soil pores. Therefore, values of porosity tend to be higher for sandy soils when compared to clay soils. As shown in ~~figure~~ 7, the higher the porosity value, then the less runoff that is generated due to increased infiltration although the model is not particular sensitive to the porosity value.<br>		The porosity value represents the volume of dry voids per volume of soil and provides the maximum moisture deficit that is available, the difference between the moisture content at saturation and at the start of the simulation. Sandy soils tend to have lower porosities than clay soils, but drain to lower moisture contents between rainfall events because water is not held as strongly in the soil pores. Therefore, values of porosity tend to be higher for sandy soils when compared to clay soils. As shown in Figure 7, the higher the porosity value, then the less runoff that is generated due to increased infiltration although the model is not particular sensitive to the porosity value.<br>
	<br>		<br>

Anne.Kolega: /* Green-Ampt Infiltration */ change 7.3.7.7, to section, as numbering can change

2026-02-24T03:03:23Z

Green-Ampt Infiltration: change 7.3.7.7, to section, as numbering can change

← Older revision		Revision as of 13:03, 24 February 2026
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	The Green-Ampt approach varies the rate of infiltration over time based on the soil’s hydraulic conductivity, suction, porosity and initial moisture content. The method assumes that as water begins to infiltrate the soil, a line is developed differentiating between the ‘dry’ soil with moisture content θ<sub>i</sub> and the ‘wet’ soil (with moisture content equal to the porosity of the soil η). As the infiltrated water continues to move through the soil profile in a vertical direction, the soil moisture changes instantly from the initial content to a saturated state. This concept is shown schematically in Figure 1.		The Green-Ampt approach varies the rate of infiltration over time based on the soil’s hydraulic conductivity, suction, porosity and initial moisture content. The method assumes that as water begins to infiltrate the soil, a line is developed differentiating between the ‘dry’ soil with moisture content θ<sub>i</sub> and the ‘wet’ soil (with moisture content equal to the porosity of the soil η). As the infiltrated water continues to move through the soil profile in a vertical direction, the soil moisture changes instantly from the initial content to a saturated state. This concept is shown schematically in Figure 1.

	Note: The Green-Ampt approach is appropriate for simulating single rainfall events where evapotranspiration and gravity-driven drainage are not significant. The 2023-03 release introduced functionality in TUFLOW HPC to allow for horizontal movement of soil water, enabling long-term simulations with multiple rainfall events. To support this, a change was implemented in the Green-Ampt equation to account for changing initial soil moisture and cumulative infiltration over time. For further details, see ~~Section 7.3.7.1.1~~ Green-Ampt (GA) in the [https://docs.tuflow.com/classic-hpc/manual/2025.1/TwoD-Domains-1.html#GA-5 <u>TUFLOW Manual</u>].		Note: The Green-Ampt approach is appropriate for simulating single rainfall events where evapotranspiration and gravity-driven drainage are not significant. The 2023-03 release introduced functionality in TUFLOW HPC to allow for horizontal movement of soil water, enabling long-term simulations with multiple rainfall events. To support this, a change was implemented in the Green-Ampt equation to account for changing initial soil moisture and cumulative infiltration over time. For further details, see Green-Ampt (GA) Section in the [https://docs.tuflow.com/classic-hpc/manual/2025.1/TwoD-Domains-1.html#GA-5 <u>TUFLOW Manual</u>].

	[[File:Fig_1_GA_Model.png\|300px\|Figure 1 Green-Ampt Model Concept]]<br>		[[File:Fig_1_GA_Model.png\|300px\|Figure 1 Green-Ampt Model Concept]]<br>

RussellGardner: /* Initial Moisture */

2026-01-26T09:47:55Z

Initial Moisture

← Older revision		Revision as of 19:47, 26 January 2026
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	In pre-2023 releases of TUFLOW, a single variable storage capacity was calculated by subtracting the initial moisture fraction from the porosity, in order to reduce memory requirements. However, in TUFLOW releases 2023 and onwards, the soil porosity and initial moisture must be stored separately to allow the soil to drain correctly when using the interflow functionality. This updated approach requires that a soil thickness be specified to calculate the soil depth. If a soil thickness is not specified when using the updated approach, an infinite soil depth is assumed for each layer and therefore different initial moisture fractions no longer have an effect on modelled results. These two approaches can generate different results when using the Green-Ampt method.		In pre-2023 releases of TUFLOW, a single variable storage capacity was calculated by subtracting the initial moisture fraction from the porosity, in order to reduce memory requirements. However, in TUFLOW releases 2023 and onwards, the soil porosity and initial moisture must be stored separately to allow the soil to drain correctly when using the interflow functionality. This updated approach requires that a soil thickness be specified to calculate the soil depth. If a soil thickness is not specified when using the updated approach, an infinite soil depth is assumed for each layer and therefore different initial moisture fractions no longer have an effect on modelled results. These two approaches can generate different results when using the Green-Ampt method.

	The three initial moisture sensitivity tests have been undertaken with the Green-Ampt method using both a pre-2023 release of TUFLOW and a post-2023 release of TUFLOW. Figure 9 shows how variations in the initial moisture affect the simulated cumulative infiltration, whereas Figures 10 and 11 show the effects of varying the initial moisture on flows at the catchment outlet when using the pre-2023 and post-2023 releases of TUFLOW. As the initial moisture is increased at the beginning of your simulation, there is less infiltration (as you are closer to soil capacity) and more runoff, causing the catchment outflows to exhibit a faster response to rainfall upstream. As the event progresses, soils become more saturated and the influence of the initial moisture parameter becomes less significant. In the examples shown here, the catchment outflows, as visible in Figures 10 and 12, show a higher responsiveness to variations in initial moisture at the beginning of the simulations, and attain higher peak values, when using the post-2023 TUFLOW releases.		The three initial moisture sensitivity tests have been undertaken with the Green-Ampt method using both a pre-2023 release of TUFLOW and a post-2023 release of TUFLOW. Figure 9 shows how variations in the initial moisture affect the simulated cumulative infiltration, whereas Figures 10 and 11 show the effects of varying the initial moisture on flows at the catchment outlet when using the pre-2023 and post-2023 releases of TUFLOW. As the initial moisture is increased at the beginning of your simulation, there is less infiltration (as you are closer to soil capacity) and more runoff, causing the catchment outflows to exhibit a faster response to rainfall upstream. As the event progresses, soils become more saturated and the influence of the initial moisture parameter becomes less significant. In the examples shown here, the catchment outflows, as visible in Figures 10 and 11, show a higher responsiveness to variations in initial moisture at the beginning of the simulations, and attain higher peak values, when using the post-2023 TUFLOW releases.

	[[File:Init moisture F10.png\|600px\|Figure 9: Sensitivity of cumulative infiltration in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model.\|border]]<br>		[[File:Init moisture F10.png\|600px\|Figure 9: Sensitivity of cumulative infiltration in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model.\|border]]<br>

RussellGardner: /* Initial Moisture */

2026-01-20T13:36:16Z

Initial Moisture

← Older revision		Revision as of 23:36, 20 January 2026
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	[[File:Initial moisture.jpg\|border\|760x760px\|Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.]]<br>		[[File:Initial moisture.jpg\|border\|760x760px\|Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.]]<br>
	'''Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.'''		'''Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.'''
	[[File:Init moisture post 2023 v2.jpg\|border\|760x760px\|Figure 12: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.]]<br>		[[File:Init moisture post 2023 v2.jpg.jpg\|border\|760x760px\|Figure 11: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.]]<br>
	'''Figure 12: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.'''		'''Figure 11: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.'''

	=== Max Ponding Depth ===		=== Max Ponding Depth ===

RussellGardner: /* Initial Moisture */

2026-01-20T13:35:02Z

Initial Moisture

← Older revision		Revision as of 23:35, 20 January 2026
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	[[File:Initial moisture.jpg\|border\|760x760px\|Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.]]<br>		[[File:Initial moisture.jpg\|border\|760x760px\|Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.]]<br>
	'''Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.'''		'''Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.'''
	[[File:Init moisture post 2023.jpg\|border\|760x760px\|Figure 12: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.]]<br>		[[File:Init moisture post 2023 v2.jpg\|border\|760x760px\|Figure 12: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.]]<br>
	'''Figure 12: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.'''		'''Figure 12: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.'''

RussellGardner: /* Initial Moisture */

2026-01-20T13:26:19Z

Initial Moisture

← Older revision		Revision as of 23:26, 20 January 2026
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	[[File:Initial moisture.jpg\|border\|760x760px\|Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.]]<br>		[[File:Initial moisture.jpg\|border\|760x760px\|Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.]]<br>
	'''Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.'''		'''Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.'''
	[[File:Init moisture post 2023.jpg\|border\|760x760px\|Figure 11: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.]]<br>		[[File:Init moisture post 2023.jpg\|border\|760x760px\|Figure 12: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.]]<br>
	'''Figure 11: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.'''		'''Figure 12: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.'''

	=== Max Ponding Depth ===		=== Max Ponding Depth ===

RussellGardner: /* In built USDA soil type */

2026-01-20T13:18:44Z

In built USDA soil type

← Older revision		Revision as of 23:18, 20 January 2026
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	== In built USDA soil type ==		== In built USDA soil type ==
	The model was also run with the default in-build USDA soil types. Figure 11 shows the outputs. As expected the higher the soil type, then typically the more the infiltration and the lower the produced runoff. Soils 8-11, which represent sandy soils do not show any runoff in this example as the rainfall applied directly to the mesh is all infiltrated.<br>		The model was also run with the default in-build USDA soil types. Figure 12 shows the outputs. As expected the higher the soil type, then typically the more the infiltration and the lower the produced runoff. Soils 8-11, which represent sandy soils do not show any runoff in this example as the rainfall applied directly to the mesh is all infiltrated.<br>
	<br>		<br>
	[[File:Soil Type.jpg\|border\|760x760px\|Figure 11: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the USDA soil type parameter in the Green-Ampt infiltration model.]]<br>		[[File:Soil Type.jpg\|border\|760x760px\|Figure 12: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the USDA soil type parameter in the Green-Ampt infiltration model.]]<br>
	'''Figure 11: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the USDA soil type parameter in the Green-Ampt infiltration model.'''		'''Figure 12: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the USDA soil type parameter in the Green-Ampt infiltration model.'''

	== Summary ==		== Summary ==

RussellGardner: /* Initial Moisture */

2026-01-20T13:18:23Z

Initial Moisture

← Older revision		Revision as of 23:18, 20 January 2026
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	'''Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.'''		'''Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.'''
	[[File:Init moisture post 2023.jpg\|border\|760x760px\|Figure 11: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.]]<br>		[[File:Init moisture post 2023.jpg\|border\|760x760px\|Figure 11: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.]]<br>
	'''Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.'''		'''Figure 11: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.'''

	=== Max Ponding Depth ===		=== Max Ponding Depth ===

RussellGardner: /* Initial Moisture */

2026-01-20T13:17:54Z

Initial Moisture

← Older revision		Revision as of 23:17, 20 January 2026
Line 136:		Line 136:
	In pre-2023 releases of TUFLOW, a single variable storage capacity was calculated by subtracting the initial moisture fraction from the porosity, in order to reduce memory requirements. However, in TUFLOW releases 2023 and onwards, the soil porosity and initial moisture must be stored separately to allow the soil to drain correctly when using the interflow functionality. This updated approach requires that a soil thickness be specified to calculate the soil depth. If a soil thickness is not specified when using the updated approach, an infinite soil depth is assumed for each layer and therefore different initial moisture fractions no longer have an effect on modelled results. These two approaches can generate different results when using the Green-Ampt method.		In pre-2023 releases of TUFLOW, a single variable storage capacity was calculated by subtracting the initial moisture fraction from the porosity, in order to reduce memory requirements. However, in TUFLOW releases 2023 and onwards, the soil porosity and initial moisture must be stored separately to allow the soil to drain correctly when using the interflow functionality. This updated approach requires that a soil thickness be specified to calculate the soil depth. If a soil thickness is not specified when using the updated approach, an infinite soil depth is assumed for each layer and therefore different initial moisture fractions no longer have an effect on modelled results. These two approaches can generate different results when using the Green-Ampt method.

			The three initial moisture sensitivity tests have been undertaken with the Green-Ampt method using both a pre-2023 release of TUFLOW and a post-2023 release of TUFLOW. Figure 9 shows how variations in the initial moisture affect the simulated cumulative infiltration, whereas Figures 10 and 11 show the effects of varying the initial moisture on flows at the catchment outlet when using the pre-2023 and post-2023 releases of TUFLOW. As the initial moisture is increased at the beginning of your simulation, there is less infiltration (as you are closer to soil capacity) and more runoff, causing the catchment outflows to exhibit a faster response to rainfall upstream. As the event progresses, soils become more saturated and the influence of the initial moisture parameter becomes less significant. In the examples shown here, the catchment outflows, as visible in Figures 10 and 12, show a higher responsiveness to variations in initial moisture at the beginning of the simulations, and attain higher peak values, when using the post-2023 TUFLOW releases.




	As you increase initial moisture at the beginning of your simulation, you experience less infiltration (as you are closer to the soil capacity), therefore have more run-off and a quicker response. Figure 9 shows the degree of change to cumulative infiltration with varying initial moisture and the effect on the catchment can be seen in Figure 10. As the event progresses, soils become more saturated and the influence of the initial moisture parameter becomes less significant.



	[[File:Init moisture F10.png\|600px\|Figure 9: Sensitivity of cumulative infiltration in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model.\|border]]<br>		[[File:Init moisture F10.png\|600px\|Figure 9: Sensitivity of cumulative infiltration in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model.\|border]]<br>
	'''Figure 9: Sensitivity of cumulative infiltration in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model.'''<br>		'''Figure 9: Sensitivity of cumulative infiltration in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model.'''<br>
	[[File:Initial moisture.jpg\|border\|760x760px\|Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model.]]<br>		[[File:Initial moisture.jpg\|border\|760x760px\|Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.]]<br>
	'''Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model.'''		'''Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in pre-2023 release of TUFLOW.'''
			[[File:Init moisture post 2023.jpg\|border\|760x760px\|Figure 11: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.]]<br>
			'''Figure 10: Sensitivity of simulated flow at the Cefn-Brwn gauge location in the Plynlimon Gwy catchment to the initial moisture parameter in the Green-Ampt infiltration model in post-2023 release of TUFLOW.'''

	=== Max Ponding Depth ===		=== Max Ponding Depth ===