EXPLAINER: World Cup host Qatar relies on desalination

WASHINGTON (AP) — Arid and surrounded by the salt waters of the Persian Gulf, World Cup host Qatar is among the world's most water-stressed countries. The nation of 2.9 million people has no rivers, and receives less than four inches (10 centimeters) of rain per year on average.

It's a condition the wealthy Persian Gulf emirate has largely paid its way out of, thanks to expensive technology known as desalination that makes seawater drinkable.

In doing so, Qatar isn't alone. Fellow Gulf Arab monarchies Bahrain, Kuwait, Oman, Saudi Arabia and United Arab Emirates also lack freshwater and depend on desalination. Israel does too. But the solution comes at a cost: Removing salt from seawater is energy-intensive, burning lots of fossil fuel. It also creates a byproduct that, when discharged into the ocean, can affect marine ecosystems.

Here's a look at the country's water supply and the role of desalination.

WHAT IS DESALINATION?

A process that makes freshwater, which humans can consume, from seawater.

Desalination plants draw water from the ocean through large pipes and blast it through fine membranes that allow water molecules to pass, but keep the salt out. That process is known as reverse osmosis.

There are other types of desalination but reverse osmosis is the most common. Inland brackish waters can also be desalinated.

WHERE IS IT USED?

Desalination plants are scattered along coastlines across the world, but the highest-capacity plants are located in high-income, water-starved Middle Eastern countries with ample coastline, such as Saudi Arabia, the United Arab Emirates and Israel. Saudi Arabia is home to the world's largest plant.

Reverse osmosis technology has been around since the 1950s. Gulf Arab nations were among the first to embrace it. After soaring oil...