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These maps of water use show why the Western US is in trouble

Justin Sullivan/Getty Images

The American West has been wrestling with drought for the past 15 years. California is now facing its worst dry spell in at least a century. So, not surprisingly, the question of how best to manage America's scarce freshwater supplies is coming up more frequently.

To that end, the Hamilton Project recently published a helpful primer, "Nine Economic Facts about Water in the United States." The whole thing's worth reading, but four maps and charts in particular stuck out. For starters, some of the driest states in the West actually have some of the highest rates of household water use:

1) Household water use is higher in the driest states — thanks to lawn watering

(The Hamilton Project)

Why do households in arid Utah use so much more water than in, say, Maine? The main factor, the authors note, is outdoor watering for lawns and gardens. "Whereas residents in wetter states in the East can often rely on rainwater for their landscaping, the inhabitants of Western states must rely on sprinklers."

This seems perverse. And, indeed, many Western states are starting to crack down on this practice. California's per capita water use has been declining in recent years, the authors note, thanks to "pricing incentives and mandatory installation of water-saving technologies, such as restricted-flow showerheads and low-flow toilets." And cities like Las Vegas have been experimenting with programs that get people to use desert-friendly plants in their lawns.

Heavy-handed water regulations can have some effect. California's towns and cities used 29 billion gallons of water less this August than they did last August — in part because of a variety of state and local restrictions enacted in response to the ongoing drought. Still, some experts think that wasteful water use will continue so long as water is cheap and underpriced. More on that below.

2) Agriculture remains the biggest water user by far

agriculture water

(The Hamilton Project)

It's worth noting, however, that homes typically aren't the biggest water consumers in the West. In California, agriculture accounts for 80 percent of state water withdrawals. (The state is responsible for roughly one-third of the country's vegetables and two-thirds of its fruits and nuts.)

But here's a twist: The report notes that the share of water used for agriculture in California has actually declined since 1980 — in part because farmers are using more efficient irrigation techniques and planting crops that generate more value with less water.

Still, these improvements aren't as widespread as they could be. Among other things, the report notes that California's farmers still use an enormous amount of water to plant alfafa during summer months, when water is scarce — even though yields and quality are low. That's "due in part to restrictions on water trading, as well as to the relatively low water prices charged to farmers."

Both of the factors above — inefficient water use in both homes and farms — could become an even bigger problem in the years ahead, thanks to the fact that population growth is now booming in many of America's driest states:

3) The driest states are now growing the quickest

population growth driest states

(The Hamilton Project)

The states with the biggest projected increase in population between 2010 and 2040 are Arizona, Colorado, Idaho, Montana, New Mexico, Nevada, Utah, and Wyoming. One thing they all have in common? Low rainfall and relatively scarce water supplies.

"These population shifts suggest that Americans will increasingly live in the driest areas of the country," the report notes. "And since population growth affects demand for water, the population shift toward drier states will exacerbate water-related challenges and put a strain on existing water infrastructure if the growth is not met with progressively greater conservation efforts."

Indeed, the U.S. Department of Agriculture has already projected that many states in the Southwest will struggle to provide enough water for everyone in the years ahead. And the situation will only get worse if global warming makes droughts more frequent and intense in the region, something that climate modelers now expect.

So what's this region to do? In a recent interview, David Sedlak, author of Water 4.0, pointed to a variety of potential future technologies that could help drought-plagued regions, like water recycling or desalination. The hitch? Some of these technologies have drawbacks (desalination uses an enormous amount of energy), they're often expensive, and there are plenty of barriers to adopting new technologies.

One big barrier, many water economists would say, is that most people don't actually pay the full price for water, which does two things. It gives people little incentive to conserve, and it gives utilities little incentive to invest in more efficient infrastructure. Indeed, the report report has one final chart that gets at the pricing issue a bit:

4) And water prices vary wildly from region to region

water bills

(The Hamilton Project)

"The price that households pay for water is highly variable across cities," the report notes, "even when controlling for the volume of water that different households use."

What's interesting is that many cities in dry areas — Denver, El Paso, Phoenix, Las Vegas — have some of the lowest water bills around, whereas a wet city like Seattle has much higher bills. Some of that can be explained by provisions in the Clean Water Act that required cities like Boston to upgrade their sewage-treatment systems. Still, the disparity is notable. Other surveys have also found that there's little relationship between the price of water and how scarce it is.

The report notes that some cities, like Phoenix and Los Angeles, have begun to reform their pricing schemes so that heavier water users get charged more.

But this is hardly universal. In most parts of the United States, the price of water doesn't reflect the infrastructure costs of delivering that water or the environmental damage that excessive water withdrawals can cause. As long as that's the case, there are few market incentives to conserve or allocate water more efficiently.

The Hamilton Project has also released two new papers on how water markets and more accurate water pricing could help spur conservation — this goes for households, cities, farmers, power plants, and a variety of water users. Both papers are worth reading for anyone who's interested in water issues. Over at The New York Times, Eduardo Porter also has a good write-up of the research.

Further reading

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

Over at Ensia, Cynthia Barrett has a nice related piece on the subject: "Hey, America: It's time to talk about the price of water"