Talk:Evapotranspiration

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Section sizes

Section size for Evapotranspiration (19 sections)
Section name	Byte count	Section total
(Top)	2,663	2,663
Definition	4,222	4,222
Influencing factors	203	7,747
Primary factors	2,104	2,104
Secondary factors	26	5,440
Vegetation type	1,687	1,687
Vegetation coverage	3,009	3,009
Soil and irrigation	718	718
Measurements	73	5,067
Direct measurement	507	507
Indirect estimation	268	4,487
Catchment water balance	686	686
Energy balance	1,197	1,197
Estimation from meteorological data	2,336	2,336
Potential evapotranspiration	85	85
List of remote sensing based evapotranspiration models	5,111	5,111
See also	375	375
References	30	30
External links	804	804
Total	26,104	26,104

Comments[edit]

just wondering: in interception by plant leaves part of evapotranspiration or should it be treaded separately?

intercepted water is just a "container", like ponded water. Evaporation from intercepted water is part of evapotranspiration, just like evaporation from ponded water. You can think of interception as a pond on top of the leaves. What may confuse the issue is that, in some cases, in particular when calculating stress, one treats evaporation from intercepted water as if it was real transpiration and not "just" evapotranspiration. Per Abrahamsen 13:45, 2004 Sep 16 (UTC)

Potential evapotranspiration (PET)[edit]

Should the text on PET be moved to its own entry? (potential evapotranspiration) Or should PET point here, and get its own space? Daniel Collins 15:30, 18 May 2005 (UTC)[reply]

It should be moved. The equations also refer to potential evapotranspiration or reference evapotranspiration (which is PET on a reference surface, usually short grass). Per Abrahamsen

I've now used the excerpt function for this. EMsmile (talk) 10:25, 21 February 2024 (UTC)[reply]

Too Technical[edit]

I added a notice about the article being too technical and needing to be expanded. This is because in no place does the article introduce what the concept of evapotranspiration refers to. Canthony 23:34, 17 October 2005 (UTC)[reply]

Less technical, or more[edit]

I added some stuff to try to make this easier to understand, mostly practical applications. I added a short definition for evaporation and transpiration because it's important to understand what they are in the context of land management and understanding the importance of evapotranspiration.

Also, since there is a PET page now, the PET section here should be trimmed down.

Done (by using an excerpt). EMsmile (talk) 10:25, 21 February 2024 (UTC)[reply]

link is an ad[edit]

I haven't studied the Wikipidia policies closely enough to understand its position on advertising. But I wanted to point out that the final link on this page is totally an advertisement. Climate based irrigation controllers, including those that use evapotranspiration formulas or data, can be very useful for conserving water. But there are many on the market. The ad seems inappropriate.

This is the title of the link in question: Add Evapotranspiration Functionality to your Home Sprinkler System

I would suggest a link to the Smart Water Application Technologies website connected to the Irrigation Association for information about ET based controllers.

http://www.irrigation.org/gov/default.aspx?pg=swat_intro.htm&id=105

and/or

http://www.irrigation.org/swat/default.asp

Beth

I agree Lotusduck 21:10, 17 December 2005 (UTC)[reply]

Reverted vandalism by 205.188.116.7[edit]

It's a shared AOL web proxy server with an extensive block log. :P HEL 04:05, 8 October 2006 (UTC)[reply]

need a simple explanation[edit]

Dear Scientists, I am trying to understand what "evapotranspiration" + "intercepted water" really means in order to think about positive applications which it can be used. For example the Tamarisk plant consumes a lot of water, not just fresh water but salt water as well. It has the ability to convert it through it's leaves to fresh water and shed the salt. I also read that it also does "evapotranspiration". Does this mean that it sweats water? If this was done say in a greenhouse feeding it saltwater would one be able to collect fresh water through artificially generated "evapotranspiration" ?!?

7cows 11:52, 06 Feburary 2007

The scenario you posed seems slightly confusing or counterintuitive. It doesn't seem like a plant would expel fresh water and keep only the salts within itself. The Tamarix article implies that salt is excreted from the plant while the water is contained within. Perhaps you could post the exact words of your source?

I'm not sure what the context is for "intercepted water", but in the context of hydrology, it could mean the water that falls and remains on a plant (e.g., the drops that remain on the leaves after a storm, which might later evaporate). It is "intercepted" because it will not go into the watershed as runoff (e.g. into a creek-->lake-->river-->ocean) and it will not go into a subsurface aquifer via "infiltration" (e.g. into the soil-->into a shallow aquifer-->emerge from a spring-->flow into a river-->ocean). That's my guess, but I cannot tell without the context. I hope that this helps somewhat. Ufwuct 10:28, 9 March 2007 (UTC)[reply]

Potential evapotranspiration and reference evapotranspiration[edit]

There are usually some misunderstandings using the terms potential evapotranspiration and reference evapotranspiration. The summary on the top of the page for potential evapotranspiration actually refers to the reference evapotranspiration. The reference to the short well kept crop in the definition is now defined as a theoretical grass with albedo 0.23, a crop height of 12 cm and a fixed bulk surface resistance of 70 m/s. Using this crop cover, the reference evapotranspiration can be calculated.

The potential evapotranspiration refers to the actual crop cover on the land surface. A crop like alfalfa will have a higher potential evapotranspiration that the theoretical grass crop, due to a larger leaf area index and a lower bulk surface resistance. It is still a potential evapotranspiration, though, since the availability of water, or the lack thereof, may result in a lower actual evapotranspiration.

The actual evapotranspiration is thus related to the potential evapotranspiration through the use of a stress factor (Ks). The relation between a specific crop (or soil cover) with the reference evapotranspiration is expressed through the use of a crop coefficient (Kc). A crop coefficient of 1.2 means that the actual crop cover has a potential evapotranspiration that is 1.2 times higher than that of the theoretical grass crop.

In equations:

ETpot = kc * ETref

ETact = ks * ETpot

or

ETact = kc * ks * ETref

Based upon FAO56: "Crop Evapotranspiration - Guidelines for computing crop water requirements" FAO Irrigation and Drainage paper 56. Richard G Allen, Luis S Pereira, Dirk Raes and Martin Smith, Rome, 1998

Rwos 12:36, 15 April 2007 (UTC)[reply]

—The preceding unsigned comment was added by Rwos (talk • contribs) 12:35, 15 April 2007 (UTC).[reply]

Estimating evapotranspiration[edit]

The "estimating evapotranspiration" section needs to be modified. It is not true that it is impossible to directly measure evapotranspiration; eddy covariance techniques do just that, and are widely used in research applications. 68.101.71.183 13:55, 6 November 2007 (UTC)[reply]

Energy balance formula[edit]

is the used energy balance formula correct? according to the FAO (document 56; Crop evapotranspiration Chapter 1), it should be Rn = G + H + λET —Preceding unsigned comment added by 137.224.252.10 (talk) 13:48, 19 November 2007 (UTC)[reply]

External links modified (January 2018)[edit]

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Small restructuring of the subsection “Hydrometeorological equations”[edit]

This subsection has one paragraph. I suggest to divide it into two.

The first part starts from the beginning and goes to “Hargreaves” and is modified. (the rest of the paragraph is not modified)

The modification is a restructuring and not content change. So, I suggest to replace the first part with the following: (Bold means a Wikipedia link already exists):

There are a wide variety of equations that estimate ET, such as:

Penman equation is the most general in calculating reference ET.

Penman-Monteith this variation is recommended by the Food and Agriculture Organization [6] and the American Society of Civil Engineers [7].

Blaney-Criddle equation was popular in the Western United States for many years but it is not as accurate in a region with higher humidity.

Hargreaves equation was also originated in the Western United States.

Makkink equation must be calibrated to a specific location.

If I don't hear anybody on this formatting, I will go ahead and make the changes in a couple of days. Mitral8 (talk) 13:29, 4 January 2021 (UTC)[reply]

This would take it from prose to a list format. The existing non list version is more appropriate. See MOS:PROSE Using a paragraph break to separate the two sections may be more beneficial. ThinkHat (talk) 15:19, 5 January 2021 (UTC)[reply]

As I mentioned, the restructuring did not change the content, in other words, prose and list give the same wording. Anyhow, I am new and thank you for explaining. I will not change it into list and will divide into two paragraphs.Mitral8 (talk) 00:57, 6 January 2021 (UTC)[reply]

Explain the linkage with climate change?[edit]

I was just doing some work on the drought article and content about "evaporative demand" brought me here. I guess this relates to potential evapotranspiration. See e.g. this sentence "Globally, the occurrence of extreme events, such as droughts, has increased as a result of the increase in temperature and atmospheric evaporative demand" (from this publication). I have no particular expertise in this but am just helping to improve the content on Wikipedia that relates to the effects of climate change. EMsmile (talk) 10:29, 21 February 2024 (UTC)[reply]