Is Agriculture Sucking Fresh Water Dry?

sciencehabit writes "The average American uses enough water each year to fill an Olympic-sized swimming pool, and global agriculture consumes a whopping 92% of all fresh water used annually. Those are the conclusions of the most comprehensive analysis to date of global water use, which also finds that one-fifth of humankind's water consumption flows across international borders as 'virtual water' — the water needed to produce a commodity, such as meat or electronics, if the ultimate consumers were to make it themselves rather than outsource its growth or manufacture."

Comments

Solution

[Errol backfiring]

if the ultimate consumers were to make it themselves rather than outsource its growth or manufacture.

There are some good solutions in The Humanure Handbook. That does not change corporate agriculture, but a little awareness on our behaviour is a good thing.

As Mark Boyle (The Moneyless Man) once said: if we knew how hard it was to purify our drinking water, we sure as hell wouldn't shit in it.

Re:The real questions should be different

[nanoflower]

It's true that we can use much less water in growing our food but it's not easily done. More to the point it's not done cheaply and that's the biggest issue. So long as it adds to the cost of food (even if it's only pennies to a pound of tomatoes) there's going to be an issue with getting the majority of farmers to change their practices. Especially in third world countries where getting those improved practices out to the farmers can prove difficult.

It's certainly a worth while thing if an area is experiencing a lack of rainfall (as in much of Africa) or if their aquifer is beginning to run low (apparently an issue in some areas of the Outback in Australia) but without some incentive it's going to be difficult to get people to change.

Re:The real questions should be different

[Gordonjcp]

Here's a novel idea - you could try not feeding corn to cows. They can't eat it anyway, so it's a collossal waste of resources.

Here's a hint - most of the world's farmland isn't rolling midwestern cornfields. Most of the world manages to raise livestock just fine.

Partly it's a question of preference - Americans like bland greasy meat, so their livestock farming practices reflect that.

It's all to do with pricing

[Colin Smith]

The perception is that when something is cheap, it is of low value so it doesn't matter if you consume too much of it.
If you look at areas where water is scarce and where wars are fought over it, or where it has to be desalinated i,e, it's expensive, you'll find the users are a lot more careful over how much is used and how it is used.

Compare US irrigation methods:
http://en.wikipedia.org/wiki/File:Irrigation1.jpg

with Persian Qanat methods:
http://en.wikipedia.org/wiki/Qanat

Re:It's all to do with pricing

[Rostin]

1. That's a typical method of irrigation in the US only in the loosest sense of the word 'typical'. What you've managed to find is a picture of an antique. My dad has a 20-year-old center pivot sprinkler that has low pressure dropped nozzles to reduce evaporation and soil compaction as much as possible, and it was old technology even back then. Center pivot means just what it sounds like. One end is fixed, and the other end goes around in a giant circle.

The nozzles on these machines vary in size from the center (i.e. near the pivot) to the end. Think about it: The drops near the pivot go around the circle much more slowly than those on the end, and so if the nozzles were all the same size, a lot more water would be put out near the center. Also, the water pressure is higher there since it hasn't undergone friction losses through the length of the sprinkler. During the first summer that my dad owned that machine, I remember walking down it several times with a dot matrix print out in one hand and a bucket of nozzles in the other, replacing them one at a time to try to evenly distribute the supply of water as much as possible.

A half-mile-long sprinkler was (again, 20 years ago) an $80K investment over the former, low-tech system of row irrigation, and he was and is not an especially wealthy farmer. Why would he go to so much expense and trouble? In part because one of his largest expenses is pumping costs, and center pivot irrigation makes much more efficient use of water, overall.

2. I am not personally familiar with Qanats, but they appear to be a water collection and storage method, not a method of irrigation. It was surprising difficult to find quantitative information about irrigation in the middle east, but after several minutes of googling, I did find this brief, UN-produced report on irrigation in Saudi Arabia. It claims, in part:

All agriculture is irrigated and in 1992 the water managed area was estimated at about 1.6 million ha, all equipped for full/partial control irrigation. Surface irrigation [i.e. row watering, like my dad used to do] is practiced on the old agricultural lands, cultivated since before 1975, which represent about 34% of the irrigated area (Figure 3). Sprinkler irrigation is practiced on about 64% of the irrigated areas. The central pivot sprinkler system covers practically all the lands cropped with cereals.

Oh.

Re:The real questions should be different

[idji]

No, we don't. Too much of that ag produce is going into feeding cows, pigs, etc and in producing biodiesel. With biodiesel they are only counting carbon savings, and not counting water, nitrogen, phosphorous and hidden energy costs (e.g. in producing fertilizer)

Re:The real questions should be different

[Cimexus]

Indeed ... 'corn fed' meat is not the norm in most of the world. Here in Australia it's almost all grass-fed. Then again, we don't have the harsh winters that necessitate keeping cattle indoors for several months each year, so it's easier just to let em roam free and munch on the grass all year.

Incidentally, I honestly don't know why Americans prefer corn-fed meat. It seems fattier than grass-fed and doesn't taste 'right' to me, but I suppose that's simply because I grew up eating 'our' meat and got used to that taste. As you say, a preference thing.

Definitions - Tricky Things

[DeathToBill]

This study borders on sleight-of-hand to my mind. At least the way it is presented is misleading.

The headline says that 92% of freshwater use is in agriculture. What it doesn't mention is that the vast majority of that "use" of water is rain that happens to fall on farmland. We could increase that number by converting land use to arable land without changing any natural flow of water. For instance, the city of Adelaide is about the same area as the county of Cornwall and is built largely on prime agricultural land. Moving the city 100 miles North East onto unfarmable land and resuming agriculture there would noticeably increase the agricultural use of water - but it would actually be an environmentally good thing.

When it comes to diverting the natural course of water (extraction from rivers, building dams, draining lakes etc - what you might call exploiting the natural resource), the use of water in agriculture is much less - the majority here supplies water for urban residences and industry.