Take the Calvert Global Water Fund. It’s built upon an index that the fund’s sponsor, Calvert Research and Management, created to include not just companies that help supply potable water but also big users with exemplary practices, said Jade S. Huang, a vice president and environmental, social and governance portfolio manager for Calvert. While the fund owns American Water Works and Xylem, it also counts Taiwan Semiconductor Manufacturing among its 111 holdings.

“Taiwan is a water-scarce area, so Taiwan Semiconductor has developed innovative practices,” Ms. Huang said. “They recapture, refilter and reuse their water three times.” Semiconductor plants gulp down huge quantities of water, and, though Taiwan receives plenty of rainfall, it has little ability to store it. Ms. Huang said Calvert views smart water handling as prudent risk management for chip-makers like Taiwan Semiconductor. “It puts them in a better position competitively, and they’re a market leader in the semiconductor space.”

The companies in the Calvert index are divided into four subgroups — utilities, infrastructure outfits, technology providers and efficient users like Taiwan Semiconductor. Each group accounts for a quarter of the fund’s assets, Ms. Huang said. The fund returned an annual average of 8.56 percent over the 10 years that ended in June.

For water E.T.F.s, Invesco is the dominant player, with three offerings. Two of its funds — Invesco Water Resources E.T.F. and Invesco Global Water E.T. F. — are constructed around Nasdaq indexes. The holdings of the former are focused on the United States, while those of the latter are spread around the world, though companies listed in the United States account for about half its assets. The former fund returned an annual average of 9.89 percent over the decade that ended in June, while the latter returned an annual average of 8.1 percent.

Invesco acquired its third offering, the S&P Global Water Index E.T.F., when it bought Guggenheim’s line of E.T.F.s last year. Like Water Resources, this fund also invests mainly in the United States, but the two aren’t twins, said J. Jason Bloom, senior director of Global Macro E.T.F. Strategy at Invesco. Water Resources has “more focus on companies developing technology around delivering clean water,” while the S&P index fund leans more toward utilities, which make up about half of its assets, he said. The S&P Global Water Index fund returned an annual average of 11.05 percent for the decade that ended in June.