[Christoffmieger (OP)]

That’s the conclusion from a new study in the journal Water Policy, whose authors compared the water supply histories of four cities — San Diego, Phoenix, San Antonio, and Adelaide, Australia. Among the lessons learned? Urban water conservation, recycling, and desalination aren’t silver bullets. In fact, the best solution may lie upstream with farmers — saving just 5-10 percent of agricultural irrigation in upstream watersheds could satisfy a city’s entire water needs.

But the time to act is now, argues Brian Richter, a senior freshwater scientist at The Nature Conservancy and the study’s lead author — he says a global urban water crisis is already here. Below, Richter tells us more about what cities need to do to say on the right side of dry.

- Many cities take a similar pattern of water development, according to your research – going from exhausting local surface and groundwater supplies to importing water to implementing water conservation to finally recycling water or desalination. Why is this pattern unsustainable?

- Are we looking at a crisis in securing urban water supplies in the near future, either for U.S. cities or globally?

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[CliffordK]

The people in the cities need the farmers to produce their food, of course.  Agriculture can be very water intensive. 

Bath water, toilet water, etc all gets more or less recycled, although waste water treatment does involve a lot of water evaporation. 

HOWEVER, cities, especially in arid regions don't need lots of green grass everywhere.  They can choose landscaping that is consistent with the amount of water availability.  And, why do cities with reservoirs not being replenished, and approaching critical water levels also boast some of the largest fountains in the world?

Potentially if solid and liquid waste could be separated earlier in the processing, then it might be easier to treat and release the liquid waste.  But, the entire modern septic systems depend on water moving the waste solids through the pipes.

[cheryl j]

Is the water issue about having "enough" water, water in the right places, or clean water? Even when agriculture uses it, it doesn't really disappear or get trapped somewhere. It isn't being used up like fossil fuels. Is the water issue really about the energy it takes to get water from point A to point B or remove contaminants?

Some other questions - When water evaporates, are all the contaminants removed? Is rain pure H2O?
Can salt water be used for bathing, toilets, laundry, and other non-drinking house hold stuff?. I'm sure a lot of people wouldn't want to bathe in salt water, but if it was a difference between a shower and no shower, I would.

[CliffordK]

I'm not sure about using ocean water in the house.  It has a lot of salt.  One could certainly flush with salt water provided one had a redundant plumbing system bringing it into the house, and was careful about the types of pipes used both bringing it in, and the drains too. Perhaps PVC/PEX & ABS.  Maybe even upgrades on the toilets too.  Would dry salt get everywhere?

It might be a problem as the water might need to be evaporated, and the sludge would then be contaminated with salt too.  I.E.  no fertilizing with the sludge.

Water does get "recycled", and yes, a part of it is elevation.  Although, with agriculture, some water would soak deep into the ground.  Some would evaporate, and of course, some is used by the plants (transpiration).  And field runoff may be contaminated with pesticides, herbicides, and fertilizers.

Anyway, water does get used over and over again.  Evaporated water, of course, may also fall as rain somewhere else.