“Great Opportunity in China” isn’t a headline we have seen much this year. Yet U.S. companies from spigot manufacturers on up should have figured out by now that there are sales to be made in helping China solve its growing water ­scarcity problem.

They certainly recognize that inside the offices of locally based companies like Pentair and Ecolab, the biggest of an emerging Minnesota cluster of companies that make products to conserve and clean water.

Market size and growth rate ­estimates vary, of course, but even the cautious view says the market for this technology should grow two or three times faster than the Chinese economy. While economic growth has slowed, it is still ­chugging along at about 7 percent per year.

“China is a bit of an acute case of what the world is facing,” said Christophe Beck, an executive vice president for Ecolab and leader of a business that Ecolab has branded Nalco Water. “We see it in ­California, we see it all over.”

Beck and other Ecolab executives scratch their heads, wondering why a looming shortage of clean water isn’t the kind of problem that’s top of mind for government officials pretty much everywhere. Beck said that by Ecolab’s estimate there is slightly greater demand today for fresh water around the world than can be supplied. A water scarcity problem, in other words, is already upon us.

If present trends continue, Beck said, by 2030 there will be 40 percent more clean water needed than the world can supply or the Earth can replenish. At least three quarters of the world’s biggest economies by then will be in what Beck called “high water stress.”

That is what makes China so interesting. What has happened in China, Beck said, is only that it developed a terrible water-scarcity problem before the rest of the biggest economies did.

The scale of China’s problem is difficult to fully grasp. What we all think we know about China is still largely accurate, that the great economic growth that has taken place since the late 1970s liberalization of the economy has come at the expense of appalling pollution of its land, air and water.

Imagine living in China and hearing earlier this year that a Chinese ministry found that water from nearly half of the country’s aquifers shouldn’t be used for drinking water.

The Chinese government isn’t exactly known for shining a bright light on national problems, Beck said, yet it has also concluded that water from 19 percent of the rivers and more than a third of the lakes and basins in China shouldn’t even be used for agriculture or industry. Of course, if you shouldn’t water the plants with it, don’t try to drink it.

And as Beck pointed out, China still would have had a water-scarcity problem even if it had managed to keep the water it had a lot cleaner. Roughly one in five people on the planet is Chinese, yet China only has about 7 percent of the world’s freshwater supply. According to an in-depth look at the opportunities for water technology producers published this summer by analysts at RBC Capital Markets, more than 400 Chinese cities now suffer from water shortages and at least 280 million people in China lack safe drinking water.

What has changed lately, though, is that the Chinese won’t put up with bad water or water shortages any more.

In China, the central government still runs things, and last year the government produced its so-called Water Ten Plan to set standards for industrial water discharge, water efficiency and other measures. The latest of the government’s big Five-Year Plans has allocated the equivalent of about $63 billion just to domestic wastewater treatment projects, a big jump from the past rate of investment.

Ecolab’s growth strategy for years was to follow its big U.S. customers around the globe, so if Marriott opened a hotel in Beijing, Ecolab would be there providing services. In China, it is more likely to be going directly to Chinese producers now, Beck said, and big customers for Ecolab have come out of China’s steelmaking and papermaking industries.

One of the things that Beck finds interesting about China’s response to its water crisis is that it is not seeking to reproduce in China the same kind of water treatment infrastructure that exists in North America or Europe. Instead it is looking for ways to leapfrog it.

One approach is the water treatment strategy of the Tianjin Eco-city industrial park. The idea there, with Ecolab’s help, is to take in the water and not let it leave the park, being endlessly cleaned and used again.

The opportunity in China isn’t all with large projects or just with the government support. It should be no surprise that the consumer market for products used to treat water in apartment units and houses is also huge there. It is at least $4 billion annually, according to RBC, and is expected to grow at perhaps 20 percent a year.

How the developing boom in the Chinese water sector boosts the Twin Cities economy is a little trickier to understand, because companies like Ecolab are not making all of their chemical water treatments and equipment here and then shipping them. At last count, Ecolab had about 4,000 employees in China. The firm’s advanced research-and-development jobs are here, though, and employment in St. Paul and Eagan is up over 2,600.

Steve Riedel of the Minnesota Trade Office pointed to other Twin Cities employers that are well positioned to sell more in China, including local operations of General Electric Co. and Dow Chemical Co., corporate parents of Twin Cities’ innovators in so-called membrane technology. This kind of water ­technology, according to a U.S. Department of Commerce study, could have a 30 percent annual growth opportunity in China.

It is also worth noting that the Minnesota players in water technology have an opportunity to sell a lot more of what they make in lots of other markets. Ecolab’s Beck said China isn’t alone as a great growth opportunity, listing the United States as just as exciting over the long term.

“While China has recognized the problem and that they need to do something, hence the Five-Year Plan and the Water Ten Plan, that’s not true in the U.S., unfortunately,” Beck said. “[But] I think it’s going to come.”