The ETF  has 37 components and the top holdings include Energy Recovery 5.0, Watts Water Technologies 4.2% and The Gorman-Rupp Co. 4.2%.

FIW is up 22.0% year-to-date.

The PowerShares Global Water Portfolio (NYSEArca: PIO) tracks global companies that create products designed to conserve and purify water for homes, businesses and industries.  PIO has a 0.75% expense ratio.

The fund has 36 components and the top holdings include Veolia Environnment 8.3%, Severn Trent 8.1% and Flowserve Corp 8.1%.

Country allocations include U.S. 47.3%, U.K. 16.1%, France 12.4%, Brazil 7.1%, China 4.6%, Japan 4.4%, Switzerland 4.1%,  Malaysia 1.5%, Finland 1.2% and Singapore 0.7%.

PIO is up 19.8% year-to-date.

The PowerShares Water Resources Portfolio (NYSEArca: PHO) tracks U.S. companies that create products designed to conserve and purify water for homes, businesses and industries. PHO has a 0.62% expense ratio.

The fund has 29 components and the top holdings include Xylem Inc 8.3%, Flowserve Corp. 8.2%, Pentair 8.1%.

PHO is up 16.0% year-to-date.

For more information on the water industry, visit our water category.

Max Chen contributed to this article.