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The US now uses less water than it did in 1970

This is an amazing chart from Peter Gleick of the Pacific Institute:

US GDP in $2005; Water Withdrawals in cubic kilometers per year. Data from USGS and USBEA. (Peter Gleick)

The US economy keeps expanding and the population keeps growing. But we actually use less water now for all purposes than we did back in 1970. That includes freshwater for our showers and toilets. It includes farm irrigation. It also includes withdrawals of both fresh and saline water to cool our fossil fuel and nuclear power plants.

The underlying data comes from a new report by the US Geological Survey, which notes that water for power plants (45 percent) and irrigation (33 percent) still made up most water withdrawals in the US as of 2010.* But use in both of those areas has been declining over time.

Some of the credit goes to major efficiency gains: Power plants have implemented more efficient cooling systems that either recirculate water or use "dry" cooling. More and more farmers are turning to drip irrigation and other efficient watering methods (though this is far from universal). Inside homes, toilets and showers have become much more efficient. And recycling of wastewater has become more common in some cities.

But that's not the whole story: The USGS also notes that some manufacturing facilities that once used a fair bit of water for industrial purposes have moved overseas. (Industry currently makes up just 4 percent of US water withdrawals, mining and drilling make up 1 percent, and domestic uses make up 1 percent.)

Now, despite these improvements, parts of the United States — particularly the drought-stricken West — are still facing serious water shortages. And the problem will only get worse if climate change dries out the region and cities in arid regions keep growing. That's why some experts have suggested better market pricing of water (so that the cost of water reflects its scarcity) and new technologies to help drive further recycling and conservation.

But what the chart above shows is that massive efficiency improvements really are possible — and water use doesn't have to rise in lockstep with economic and population growth.

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* Note on terms: This data is measuring water withdrawals: i.e., both fresh and saline water that is diverted from aquifers, rivers, or the ocean. But only part of that water is actually consumed (i.e., used and not returned to the source). So, for instance, water used for crops is both withdrawn and consumed, but water that is used to cool a power plant and then returned to a stream is only withdrawn.

These are two different measures. So that's why you'll see stats about how farming makes up just 33 percent of all withdrawals in the United States, but 80 percent of consumption. See p. 8 here for more on this distinction.

Further reading

These maps of water use show why the West is in trouble.

Could water markets help solve the American West's water crisis?

Our cities' water systems are becoming obsolete. What will replace them?