The First Trust ISE Water ETF (NYSEArca: FIW) and PowerShares Water Resources Portfolio (NYSEArca: PHO) both track U.S. companies that derive their revenue from products that conserve and purify water.

Water investing is a good way to play a long-term trend as the world still needs to find sustainable sources of potable fresh water, especially with the specter of climate change.

“Many emerging markets are also less stringent in regulations preventing the contamination of water. That means that not only is the amount of fresh water per person declining, but an increasing amount of that water is contaminated and unpotable,” according to PowerShares. “As a result, emerging market governments are funneling large amounts of capital into areas like water conservation, purification and infrastructure. Over the past decade, water infrastructure spending has grown rapidly in both absolute terms and as a percentage of gross domestic product (GDP) in most emerging markets. Emerging markets now account for half of all infrastructure spending worldwide.”

PIO is up more than 8% year-to-date.