How can you "waste" water, isn't it ... ?

it does flow back into the system, however, polluted water pollutes the closed system, and is expensive to clean up, also it is difficult and expensive to pump water to many desert areas, so if you live there wasting water means you are not only wasting your money, but you are wasting everyone else's money too. In other areas aquifers are being dried up due to overuse and agriculture, water in those places shouldn't be wasted.

But I do understand your point, where I live, water is plentiful and naturally cleaned and filtered, I have well water, so all my water is free. Most people have city water. In New England we get more precipitation which naturally refills resevroirs and aquifers than we actually use.

Expanding on the other answers--you're right that eventually water will return to the system. BUT the real question is when and where. Living as I do in the arid high desert, it can take a long time for water to return. If I "waste" water in the summer and the summer monsoons don't deliver the water that flowed downstream doesn't effectively return until after the snow melts the following spring. Even then it requires a significant snowfall to do so. So, if we have a very low snowfall, there could be drought the following year (hence that 'eventually' still didn't happen).

There's a difference between usable water and just water. The majority of water on the planet isn't usable for most purposes humans need the stuff for. For example, whilst swimming in the sea may appeal to many as being fun, it's not the sort of stuff you can actually drink. Furthermore, the amount of fresh water in the entire global supply tanks isn't necessarily of relevance to a local situation. A drought, let's say in Sudan, isn't in the least soluable simply because of the existence of billions of gallons of excellent freshwater tied up in the ice fields of Antarctica.

<<So if you use a lot of water, it will eventually flow back into the system anyway, won't it ? It doesn't magically disappear ... ?>>

It can effectively disappear should it not reappear in the right places.

Usable, drinkable water is a time-dependant finite resource. It takes time to replace the water that you consume (or waste). In areas like where I live, high rainfall and large surface water systems make water a resource that is unlikely to become depleted over the short term, because the system gets recharged faster than we can use it. In some areas, like the dry west-southwest of the US, the rate of recharge is slow relative to the rate that the water is being taken for use, so you could easily put yourself in the situation where there is not enough water available for use over the short term (short term could mean years or decades).

If you think of water like trees in the forest you might get a good sense of what I mean. It takes time for trees to grow, so if you cut down the trees faster than they can grow back, you eventually start to run short on wood. The wood isn't being replenished as fast as you are using it. If you are smart, though, you will realize that you can maintain the balance forever as long as you only take the amount of wood that can be regrown over the time period of use.

If you all use water or wood as though they will last forever in the same amount (when in reality they will not), eventually you all will be fighting over that small amount that is available for now because you made that happen. Two decades from now is too late for now, even if in two decades there will be plenty.

The water will come back, and so will the trees, unless you completely destroy the system (and that can happen, look at the lands on the fringes of the Sahara desert where they have completely destroyed the ability of the land to fix itself, and instead have converted the areas into desert).

It takes manpower, energy and special equipment and even chemicals as well as an expensive distribution system to deliver potable (drinkable) water to a house and carry used water away. Wasting water means wasting all of the combined resources including conserving the reservoir. As you say, all water will likely be recycled by the sun and Mother Nature (without a water meter!).

By definition, a cask of sewage containing a cup of wine and a cask of wine containing a cup of sewage are both sewage.

Tap water is still relatively cheap (water the lawn?) because everyone conserves it and there is usually plenty to go around.

It gets polluted. You can't drink polluted water... Or it gets dried up by the Sun. It gets hotter every Summer starting from 1998.

difficult situation. look over bing and yahoo. that will may help!