What does it mean to "use" water?

Factual Questions
1

I know this has to have been asked before, but it was on my mind after hearing an interview the other day.

The guy said that creating the plastic for a one liter bottle of water uses 3 liters of water.

We used to use 2000 tons of water to create one ton of steel. Now, we use 20 tons (something like that).

Toilets used to use 6 gallons per flush. Now, they use 2 gallons per flush.

Clearly, in all these applications, the water “used” doesn’t disappear from the face of the earth.

Just what is the savings, and the net effect on the amount of water on earth when a toilet uses 6 gallons instead of 2 gallons?

Basically, is water really “lost” somewhere along the way, or are we just trying to find ways to treat less water before adding it back to the environment.

2

Water is lost when it re-enters the earth or waterway without a second use.
My water is not lost, as it enters a septic tank and drain field and feeds my lawn.

3

That’s the same argument I always make. You really just pollute water and often not even that when leaving a sink on to brush your teeth. My preferred term would be “cycling” water because, as you note, it is all still here. I can see a problem with excessive water cycling in areas with chronic water shortages because the water may become poorly distributed in terms of its next use. However, I have never lived in an area with a water shortage so trying to save water doesnt do much good except for saving some minimal processing cost. Our water bill is unmetered and we get charged $48 once every six months. There is no reason for us to try to save water.

4

If the water is removed from a natural ‘aquifer’, it ain’t just used…it’s gone for a long time. There is a cycle, but it is tremendously long.

In the Midwest there is an aquifer than is dangerously low. Took millions of years for the water to make up the aquifer, and it’ll be drained in just a few hundred, going back over a century.

Might it have some water again? Sure, after millions of year.

I am kinda with you on this, but water can be ‘used’ more or less. Farmers in the Midwest are finding out, or might find out in our lifetime.

A must read…Presently, groundwater in the United States is utilized approximately four times faster than it is naturally replaced. So, in this case, we are using it up – Ogallala Aquifer:

5

This isn’t going to be a complete answer, but ‘used’ can be looked at a few ways.

  1. water is treated
  2. water is treated
  3. water runs downhill
  4. water is regulated

Theoretically speaking, most water is neither created nor destroyed, but cycles in one of the great cycles of life. There is only so much fresh water in the cycle, however, and the fresh water that people use usually comes from a lake, river, or well. These are replenished by rainwater and upstream runoff. There is only so much of it and most of it has to be treated before being put to use. That’s the first treatment.

The second treatment was only added in recent historical times and comes after you’ve used it and before it’s released back into the wild. I haven’t been keeping up and no longer know how many times Mississippi River water is ‘used’ before it reaches the ocean. And if the second treatment (and the time it spends in the river can add ‘treatment’) is insufficient, the first treatment for folks further down the line becomes more extensive and expensive.

Since water runs downhill, only the water coming toward you, and that you have the physical equipment to gather, is of use to you. If the water has been pulled out for irrigation, a lot of it will re-enter the water cycle as the moisture in crops, increased evaporation, and groundwater. This will not be water still available for use downstream. As an aside, some irrigation runoff water is rich in selenium, salt, and plain old silt and not only difficult to treat, but toxic if left untreated.

In some areas, water is regulated, so that you are only allowed to remove and use the amount of water that you have been given rights to. It doesn’t matter if it’s there, or if you have the equipment to pull it out, if you don’t have the rights.

The problem with aquifers has been addressed in other posts. I’d add that some of the water refreshing the aquifers is pulling minerals and fertilizers along with it. The replenished water may not be as clean as the older water.

So I guess the short answer is that water is never completely ‘lost’, but we don’t drink salt water and we have water systems that are set up to deliver a certain volume of water at a certain level of treatment. If the demand increases or the water quality declines because it has been put to increased use before it reaches the system, then you’re looking at an investment of millions to expand the system. And if everyone grabs for the same water at the same time, there might not be enough for everyone.

6

In the context of industrial processes, such as making bottles or steel, water usage is measured by the water meter(s) on the pipe(s) coming into the factory. If the factory takes a megalitre of water from the water utility, they have used a megalitre of water. Within the factory, the water might be used several times, but that reuse does not add to the consumption. However, eventually the water leaves the factory, down a sewer, into a river, into the air as water vapour, etc., or was part of the end product; and in the long term water leaving the factory will total water entering the factory.

7

Just because there aren’t water shortages doesn’t mean that the water being used is entirely replaceable. While the New England area generally enjoys adequate rainfall and readily replenished aquifers, many areas of the world would seem to have adequate water resources and yet still either depend or are economically prejudiced to using (some call it mining) of so-called ‘fossil water’ like the aforementioned Ogallala Aquifer. Even if there is adequate rainfall to theoretically replenish used water, temporary overdepletion of shallow aquifers, and in particular artesian wells (which are “self-pumping” due to hydrological pressure of the overlying substrate) can cause them to collapse and not refill. This has happened in Mexico City, causing both permanent shrinkage of aquifer capacity and measurable subsidence of the bedrock foundation, threatening the structure of buildings.

Just because water is cheap or unmetered doesn’t mean that it is not a limited resource. The tragedy of the commons is a repeated theme in human expansion. However, unless you maintain a football-field sized pool in the backyard of your Scottsdale home, the amount of water you use and waste in ordinary household use is a pittance next to the amount of “virtual water” you consume in agricultural, textile, and industrial processed products. In terms of water units, a loaf of bread costs about 1,000 gallons; a hamburger something like 1,200-1,500 gallons (depends on whether you get the cheese or not, I guess), and around 6,000 lbs for a cotton shirt.

Let the faucet flow. That’s the least of our problems.

Stranger

8

You know, unless the produce is ice, bottled water, soda-pop, and such. :wink:

Of course on preview, it’s obvious that those items are leaving the factory, too. :smack:

9

If your speaking of the recent NPR interview they where specifically talking about potable water. In which case once the water is a risk to consume it is considered used.

10

I am. I must have missed that qualification.

If anyone is interested, it’s in podcast at NPR. Pretty interesting interview.

Thanks for the replies, all.