"The worst crisis of all time, in my view, is the critical global shortage of fresh water," says " Larry Edelson. In Money & Markets, the resource expert offers four water sector plays.

"The world's water crisis is now getting worse by the day. And the global financial and credit crisis is merely one reason why.

"Another is the ongoing modernization of major parts of the world, which is increasing demand for water, while at the same time polluting it.

"Yet another is major droughts around the world, including in our own back yard, where 60% of the U.S. is officially experiencing a drought.

"New technologies and techniques for better water supply management and improved conservation on the demand side could potentially avert a worldwide disaster.

"And as a long-term investment, water is one of my favorites. For both its tremendous social cause as well as its profit potential.

"The clamor for solutions and the companies that provide them could propel overnight the relative unknowns of the water industry to legendary investment status.

"Calgon Carbon (NYSE: CCC) provides products and services to purify water and air. It manufactures granular activated carbon for removing organic compounds from water, air, and other liquids and gases.

"Calgon is a solid, $792 million company with good fundamentals ... a respected brand name ... and a moderate forward P/E around 20.87.

"Aqua America (NYSE: WTR) provides water and waste-water systems to nearly 3 million customers and on the move, acquiring over 100 smaller companies in recent years. Current revenues are about $626M, and growing.

"Pentair Inc. (NYSE: PNR). A manufacturer and distributor of fluid-handling systems and industrial products like waste-water pumps.

"Expanding in China, which is suffering through the worst water crisis on the planet. Trading now for less than 10 times earnings, Pentair is a great long-term play.

"Watts Water Technologies (NYSE: WTS), one of my favorites, Watts is a major leader in the manufacturing of valve and flow-control products.

"Watts has doubled its business in the past five years, mainly through acquisitions and via expansion overseas, where more than 30 percent of its business now comes from Europe and China."