Water is an underlying resource essential to power the economy, yet it has rarely received the same level of attention paid to greenhouse gas emissions, despite the view from scientists that water scarcity will be exacerbated by climate change.

Some sectors are more vulnerable than others: Consider that electric power plants are responsible for 40 percent of freshwater withdrawals in the U.S. Meanwhile, agriculture represents about 70 percent of water use worldwide, and even more in developing countries.

But smart companies in every sector are finding innovative ways to address the physical, reputational, regulatory and litigation risks from an increasingly water-constrained world. Their efforts -- or lack thereof -- aren't going unnoticed as investors examine the ways in which companies in their portfolios use natural resources, manage the associated risks and move to seize related business opportunities.

"If you're a publicly traded company, your owners care about this issue," according to Brooke Barton, senior manager of corporate accountability at Ceres, the investor advocacy group that promotes sustainability as a means of achieving responsible business growth.

Barton recently examined how companies in water-stressed sectors are disclosing these risks and opportunities in the recent Ceres report, "Murky Waters: Corporate Reporting on Water Risk."

While the report focuses on disclosure, it also shines a spotlight on the best practices of the largest publicly-traded companies in these water-intensive industries, which include beverage, chemicals, electric power, food, homebuilding, mining, oil and gas, and semiconductors.

There tends to be a correlation between water risk and disclosure, Barton said, meaning that industries with sophisticated disclosure practices are more likely to view the issue as a core element of their businesses. For example, the mining industry received high scores in the Ceres report. Not coincidentally, mineral extraction often takes place in areas with great water scarcity.

"Consent is incredibly important for mining companies to achieve their production goals," Barton said. "We have seen some examples that have led to the loss of license to operate."

Beverage companies, which also scored well as an industry, have long recognized the reputational risks they face from their water-intensive business model. PepsiCo now has a policy that recognizes the human right to water, the only multinational company to do so.

"I think that is a really important statement," Barton said. "They're doing a lot of work on what that means in operationalizing that on the ground."

By and large, most companies view the availability of clean potable water as their No. 1 threat, Barton said, followed by regulatory risks, mostly related to wastewater discharge.Increased water stress, population growth, and economic development in emerging nations will lead to increased scrutiny from regulators in many sectors.