Talk:Water cycle

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LOOKING AT THE RAIN CYCLE AS A HEAT ENGINE


I was wondering about the energetics of the water cycle. Water absorbs latent heat as it turns to vapour. At this point an interesting thin happens, as water vapour mixes with dry air, the resulting moist air is lighter than dry air.

The moist light air begins to rise upwards under the action of gravity, (lighter moist air rising as denser dry air comes down to replace it). At a certain altotude the vapour condences back to water and comes down as rain. However as the moist air has not preformed any 'work' the heat that the vapour gives out at the higher altitude must be exactly equal to the heat that was absorbed as the water turned to vapour at sea level.

The above may be confirmed by looking upo th Newmans Encyclopedia of Science.

Looking at the Rain cycle as a heat engine we would notice that this is one 'Heat Engine' that absorbes a quantity of heat say 'H' from a 'source' and gives bach exactly the same quantity of heat 'H' to the 'sink'.

By the application of heat and work laws the Rain cycle mut produce zero work (H - H = 0)yet a large mass of water has obtained a considerable amount of potential energy.

I would be able to give more details in a few days.

Adess Singh 17:47, 28 February 2007 (UTC)Adess Singh

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The water cycle — technically known as the hydrologic cycle or hydrological cycle — is the continuous circulation of water within the Earth's hydrosphere, and is driven by solar radiation and cloud condensation nuclei.
Other languages WikiProject Echo has identified Water cycle as a foreign language featured article. You may be able to improve this article with information from the Romanian language Wikipedia.

The text removed as follows is not accurate:

"Precipitation seldom falls in the oceans, because under normal circumstances, mountain ranges are needed to induce condensation and the formation of clouds."

I was thinking about fixing it...but removal may be the best fix. Hard Raspy Sci 02:53, 7 Feb 2005 (UTC)

Contents

[edit] Image

What happened to the image from USGS (Water_cycle.png)? --WCFrancis 13:58, 13 May 2005 (UTC)

WHAT ABOUT CONDENSATION?????

Hey, I just found this. I am with USGS and I built our Water Cycle site (http://ga.water.usgs.gov/edu/watercycle.html). We did just "adjust" the diagram in order to add "sublimation", changed "transpiration" to "evapotranspiration", and added a needed "evaporation" arrow from surface water (the lake), to show that evaporation also occurs on land.

I'm afraid there never was a PNG version, but we are trying to create a library of various sized JPGs and PDFs that users will be able to download (sadly, this depends on funding).

Email me (hperlman@usgs.gov) if you have a specific need.

Also, note the diagram is available in almost 60 languagea and we are now getting in translation of summary text.

[edit] Significant Figures

Any useful reason for reporting calculation results to 14 significant figures? -- WCFrancis 18:31, 16 Jun 2005 (UTC)

I wrote down whatever the calculator showed, leaving it up to the reader to round results as required. QUITTNER 142.150.49.171 18:51, 16 Jun 2005 (UTC)


well work harder senor

[edit] How much water ...?

Remove the following section from the article for discussion:

---------------
==How much water==

Clouds can hold only a limited amount of water:[1]

At 32°F = 0°C the specific volume is 3305.7 cu ft/lb
At 120°F = 49°C the specific volume is 203.47 cu ft/lb

Converting the reciprocal to metric, 1 lb/cu ft = 1.60x104 g/m3.

If a cloud hits a cold front, then it sheds water/hail/snow until the amount of water it holds is not above the saturation point at that particular lower temperature.

Curve fitting can help. To find out how much moisture a cloud can hold use x=°C at the cloud, and y=the maximum moisture (="at saturation") the cloud can hold in gram per cubic meter (g/m3) at that temperature, where E-6 means "times 10 to the power of minus 6", use:

y=3.19E-6*x4+1.09E-4*x3+0.0113*x2+0.327*x+4.85
An Example:
Assuming that it is known that at the cloud the temperature is 32°C, and it has just started to rain, it would be reasonable to conclude that the moisture contained by the cloud would be at the saturation level, which, at 32°C, is 33.8 g/m3. Later, when the temperature at the cloud has been reduced to 20°C, the maximum moisture the cloud can hold is only 17.3 g/m3. Therefore the amount of water that came down as rain so far is about 33.8-17.3=16.5 g/m3.

Similarly, to find out y=the minimum temperature in °C at the cloud at which the given x=amount of moisture in g/m3 can be retained by the cloud use

y=-4.94E-6*x4+9.90E-4*x3-0.0736*x2+2.84*x-11.5
==Notes==
  1. ↑  "Steam Tables. Properties of Saturated and Superheated Steam" (1940), The Superheater Company Limited.
---------------------

It seems there is a bit of confusion here. Is the section referring to water or water vapor? The saturation comments imply water vapor, but the content implies liquid water. And clouds are liquid water or ice crystals. Something amiss here. Also I don't think we need the curve fitting equations. And the outdated reference with its cu ft/lb ... surely we don't need that and can do better. Vsmith 00:29, 8 August 2005 (UTC)

[edit] Compartment or reservoir

I have a technical bias, if it's not obvious, so I should ask what term would be best: compartment or reservoir? Either way, the idea should be illustrated. Reservoir already connotes water storage, but behind a dam, and I prefer the term. What thoughts? Cheers, Daniel Collins 16:34, 27 March 2006 (UTC).

[edit] Boring!

The Water Cycle is the most boring thing you can learn

Water is limited that's true. But what this page needs is some plain simple explanations that school-aged children can understand, not all this mumbo jumbo.

[edit] Removed example: residence time

I removed the following text (which was initially added by me anyhow). I should concede it's a bit too textbookish. Daniel Collins 18:21, 7 September 2006 (UTC)

Example: Calculating the residence time of the oceans
As an example of how the residence time is calculated, consider the oceans. The volume of the oceans is roughly 1,370×106 km³. Precipitation over the oceans is about 0.398×106 km³/year and the flow of water to the oceans from rivers and groundwater is about 0.036×106 km³/year. By dividing the total volume of the oceans by the rate of water added (in units of volume over time) we obtain the residence time of 3,200 years—the average time it takes a water molecule that reaches an ocean to evaporate.
\mbox{Residence time }|\mbox{ ocean} = \frac{1370 \times 10^6 \mbox{ km}^3}{(0.398 + 0.036) \times 10^6 \mbox{ km}^3/\mbox{year}} = 3200 \mbox{ years}

[edit] What's so special about marsupials?

The text indicates that water in the atmosphere also comes through persiration from mammals and marsupials. Wikipedia specifies that marsupials are also mammals. What is so special about marsupials to make them worth mentioning separately? Could we not confine the text to mammals?

I would have done it myself if I was sure that the author of the text did not have something special in mind.

Afil 01:06, 19 September 2006 (UTC)

By all means, do make such changes yourself. Daniel Collins 15:09, 19 September 2006 (UTC)

[edit] Conservation of mass: Appropriate for this article?

I originally added it, but now I'm not so sure, so I'm moving it here. Daniel Collins 18:57, 24 October 2006 (UTC)

Average annual water transport[1]
Water flux Average rate
(10³ km³/year)
Precipitation over land 107
Evaporation from land 71
Runoff & groundwater from land 36
Precipitation over oceans 398
Evaporation from oceans 434
The total amount, or mass, of water in the water cycle remains essentially constant, as does the amount of water in each reservoir of the water cycle. This means that rate of water added to one reservoir must equal, on average over time, the rate of water leaving the same reservoir.
The adjacent table contains the amount of water that falls as precipitation or rises as evaporation, for both the land and oceans. The runoff and groundwater discharge from the land to the oceans is also included. From the law of the conservation of mass, whatever water moves into a reservoir, on average, the same volume must leave. For example, 107 thousand cubic km (107 × 10³ km³) of water falls on land each year as precipitation. This is equal to the sum of the evaporation (71 × 10³ km³/year) and runoff (36 × 10³ km³/year) of water from the land.
Water that cycles between the land and the atmosphere in a fixed area is referred to as moisture recycling.


I was wondering that myself. People pollute portions of the water supply to such a degree that a small percentage may not get back into the cycle, like in Superfund sites where there have been chemical spills and nuclear contanimation. Thegreatdr 19:08, 24 October 2006 (UTC)
Sure, it's not completely accurate at the local scale. It's just a very useful concept. Violations of the principle are usually of more interest. Daniel Collins 19:27, 24 October 2006 (UTC)
Seems fair enough for the article. There are some other terms - like groundswater storage, and aquifer mining - which might affect the small scale balance William M. Connolley 20:17, 24 October 2006 (UTC)

[edit] GA

I felt that the article satisfied all the criteria. I'm a non-specialist and I found it interesting and thorough. Congratulations. Readro 22:26, 6 December 2006 (UTC)

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[edit] Discoverer?

Who discovered the Hydrologic Water Cycle, or at least figured out the process, and when? I think that should be noted.

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