How much "new" water does respiration etc add to Earth?

Just something I was pondering about the water cycle, rising sea levels etc.

Water is a waste product of lots of natural processes: respiration, combustion being two obvious ones. Are there any estimates of how much new water is created on Earth each day/year/whatever. Is it in any way significant compared to the massive volume of water already here?

I read about the extraction of groundwater (which is essentially “new” to the water cycle), which according to Wikipedia could account for around 6% of observed sea level rises since 1900 (cite), but what about all the water produced from burning fossil fuels, and from cell respiration?

I was schooled in the fact that there is no such thing as new water: over millions of years the total remains the same, merely forming and reforming into different stages.
Mind you, they also said that sailors when drinking water would throw a little amount on the floor as a gift to those people suffering from draught. Very superstitious, the sailorman.

Yes, I heard the same thing, probably from the very same teacher who wrote chemical equations on the blackboard showing H[sub]2[/sub]O being produced. It’s clearly bollocks.

It really isn’t bollocks. It is true that some of the water that you excrete contains oxygen and/or hydrogen atoms that you ingested in the form of foods (mostly hydrogen, I guess, because most of the oxygen will have come from oxygen gas you breathed in), but those food molecules (and the molecules of oxygen you breathed in) all were, or trace back to, molecules that plants once synthesized out of carbon dioxide and water. Photosynthesis removes water from the environment, respiration (of both animals and plants) puts it back. On balance, there is less free water on the Earth because there are living things that have taken some of the oxygen and hydrogen atoms that once comprised water and used them to build other sorts of molecule, such as sugars, fats, cellulose, and proteins.

The only way to try to answer this is to define what you mean by “new”. That’s not at all clear.

Obviously, the total water supply has to be fairly constant. The Earth is a system. Unless it gets bombarded by icy comets, no new water can be added. Some water molecules can be lost from the atmosphere, but that’s a minimal number.

You seem to be referring to some short time scale. What time are you thinking about? Groundwater is merely rain that fell X number of years ago. Petroleum is merely plant material that got buried Y number of years ago. When it burns, water is one of the byproducts. Is that “new”? Under what definition?

Unless you can come up with a definition that works, the answer has to “How much “new” water does respiration etc add to Earth?” has to be none.

And don’t forget the elemental oxygen in the atmosphere, too.

I’m going to make a boat load of assumptions here:

complete combustion
C_a H_b +O_2 => aCO2 + (b/2)H2O
my rough work indicates an H2O to CO2 mass ratio of 1.9 times the H to C mass ratio of the fuel

In 2010, about 14 billion tonnes of CO2 was emitted from coal burning, 11 billion tonnes from liquid sources, and about 6 billion from natural gas.

If coal is 80%C 5%H by weight, it should produce about 119 tonnes water per 1000 tonnes CO2 for 1.7 billion tonnes of water

If crude oil is 85%C 10%H, it should produce about 225 tonnes water per 1000 tonnes CO2 for 2.5 billion tonnes of water

If natural gas is Methane, it is 75%C 25%H, it should produce about 637 tonnes water per 1000 tonnes CO2 for 3.8 billion tonnes of water

That gives us about 8 billion tonnes of new water from fossil fuels in 2010.

Here’s as estimate (very rough) for you :

Total world CO2 released in 2012 (link) = 34,500,000 thousand tonnes

Roughly 45% of this CO2 comes from Oil, 30% from Coal and 25% from gas (link - very rough assumption

The average H/C (molar basis not mass basis) ratio in Oil (Petroleum) is 2/1, in Coal it is 1/1 and in gas it is 4/1 (link)

So for each tonne of CO2 released , H2O formed is :

Oil — (18/44) = 0.4 tonne
Coal — (18/(244)) = 0.2 tonne
Gas — (18
2/44) = 0.8 tonne
So for 2012 - the estimate of water created (from hydrocarbons to molecular water) will be = (0.450.4+0.300.2+0.25*0.8)*34,500,000 thousand tonnes

**= 15,180,000 thousand tonnes ** which is around 4000 million gallons

For reference the Atlantic Ocean contains 82 million billion gallons (link)

That’s the kind of thing I was after, thanks am77494 and nolongerlurking. Pretty negligible, as I suspected.

And that really is “new” water. With respiration etc, yes you can argue that the sugars being burnt have been created using water which is then just being released, but fossil fuel burning is adding new water to the cycle. Same with groundwater, which is new in the sense that it had been locked away outside the cycle - in the same way that burning fossil fuels “adds” carbon that had previously been locked away, unlike burning wood.

This “NEW” is debatable; whatever formed coal took “water” to build/transform it, since the Earth is a somewhat closed system.
It looks to me, that burning fossil fuel just releases that trapped water back into circulation.

Only thing that is really new must come from outside of Earth – it must be imported.

You global warming advocates are like the lover caught in the act who screams. “Who you going to believe, you’re lying eyes, or me ?”

That the way you GW advocates seem to me these days.

You don’t want a free an open debate, you try and shout out and shut down any one with a differing opinion, you chide the other side for bias while ignoring your own, and when as facts go against you then you just change the name or time cycle or claim a different pattern has emerged. It really is pitiful these days watching this.

I am all for conservation, renewable energy that is cost efficient, and many other points on the green side that make sense to me. But for GW, or what ever you call it these days, you lost me years ago.

Moderator Note

davida03801, political jabs are not permitted in GQ. In addition, none of this is actually relevant to the question in the OP. No warning issued, but don’t do this again.

General Questions Moderator

I also go on the assumption of a closed loop of existing water, hydrogen, and oxygen.

However, a relatively recent development has me wondering if we are losing a wee fraction of the total. In recovery of gas and oil via hydraulic fracturing (fracking,) water is injected into the rock, miles below the water table. According to the energy biz official line, that water never returns to the aquifer.

Am I understanding that correctly?

Sure, but water isn’t an element. So there can be ‘new’ water in the system if the Hydrogen and Oxygen come from sources that weren’t water previously - O from, say, Iron Oxide, H2 from Hydrogen Sulphide.

And there can be less water in the system if the water is broken down when iron oxide and hydrogen sulphide are formed, which must also happen.

Nobody seems to be talking about the net change. Looking at one side of it is misleading.

The USGS has a great aid for putting the quantity and location of Earth’s water resources into perspective.

As others point out, water’s fate in our closed-system globe is cyclical, with water also ‘removed’ though myriad abiotic, biotic, and anthropogenic processes. It was these processes that sequestered the hydrogen and oxygen in the organic fuels (eg. coal, oil, etc) in the first place.

Such processes are included in the more sophisticated models of the hydrologic cycle. NOAA explicitly mentions combustion in their description of the global water balance components , and a Google Scholar search returns quite a number of scientific articles that attempt to answer the OP’s question.

Also, just to quibble a bit, groundwater isn’t new to the hydrologic cycle, but its extraction has led to a significant redistribution of that water within the hydrosphere :slight_smile:

Well, Hydrogen and Oxygen is limited within the closed system of earth as well.
Just think about what created these fossil fuels you are using to create “new” water – it’s dead ancient dead organisms containing water.