All people have some basic needs — so in tough times, investors naturally go to consumer staples and other defensive sectors because they’re industries sure to see activity in any environment.

Electric utility stocks like Southern Co. (NYSE:SO) or Consolidated Edison (NYSE:ED) may see a dip in energy demand, but it’s not like people will just give up on electricity — especially in the wintertime! Kraft (NYSE:KFT) and General Mills (NYSE:GIS) may sell less high-margin premium items, but families still need to eat — and mac & cheese or Cheerios remain affordable necessities.

But while investors think about shelter and food, many overlook the other necessity all humans have: water. And in this age of climate change and complicated water rights between municipalities in Texas, California and elsewhere … well, water is a hot commodity even if it’s one of the most abundant resources on the planet.

And as the globe gets more crowded, the need for safe and clean water supplies is only going to increase — which makes this a growth industry.

So, how can you cash in on the megatrend of water demand? Here are a few ways:

Pall (NYSE:PLL) is a supplier of filtration, separation and purification technologies. It mainly serves businesses, with major revenue streams (pardon the pun) coming from industrial companies that use a lot of water and life sciences businesses that need sterile and clean water either for lab work or suspension of medications. This midcap is up almost 12% year-to-date, and just set a new all-time high.

American Water Works (NYSE:AWK) is a water and wastewater utility — and like many utility stocks, is a nice dividend payer with a 2.8% yield. It has steadily been increasing both revenue and profits over the past few years, though the P/E is a bit rich for a ute at around 16 on forward 2013 earnings, but the megatrend playing out should continue to prop up future growth.

Waters Corp. (NYSE:WAT) sells analytical instruments that measure a number of things, but its flagship water-quality division focuses on testing and measuring stuff that’s in water and other liquids. Shares are up about 15% year-to-date, and the company has posted year-over-year revenue growth in 10 of 11 straight quarters and year-over-year profit growth in 11 of 12 quarters.

PowerShares Water Resources ETF (NYSE:PHO): The PowerShares Water Resources Portfolio Fund is based on the NASDAQ OMX US Water Index. Surprised there’s such a grouping? Well there is! With a reasonable 0.66% expense ratio you get a share of the biggest names in water: Pall, American Water Works, Waters Corp. as well as industrial stocks like Floserve (NYSE:FLS) and Pentair (NYSE:PNR) that provide “flow solutions” for all manner of liquids, including water.

PowerShares Global Water Portfolio ETF (NYSE:PIO): If you want to make sure you have a footprint in emerging markets and global growth for water use, then consider this ETF. It focuses on stocks that are involved in the treatment of water and services related to global water consumption, but allows you to play some companies not listed on domestic exchanges such as Japan’s Organo, the Netherland’s Arcadis and Finland’s Kemira Oyj.

Jeff Reeves is the editor of InvestorPlace.com and the author of “The Frugal Investor’s Guide to Finding Great Stocks.” Write him at editor@investorplace.com or follow him on Twitter via @JeffReevesIP. As of this writing, he did not own a position in any of the stocks named here.