This piece was co-written with Dr. Larry Brilliant, president of the Skoll Global Threats Fund.

This piece also appeared in McClatchy News and the Huffington Post.

We know less about one of world's most pressing challenges today than we did 10 years ago. It's no secret that water - or the lack thereof - will be one of the defining issues of the 21st century. And yet, the United Nations World Water Report, in 2009, stated that when it comes to water, "less is known with each passing decade."

Today marks the 20th anniversary of the first World Water Day, an international celebration designed to draw attention to the importance of freshwater resources. However, for a large and growing proportion of the world’s population, every day is a World Water Day. Difficult, complex water challenges including drought, groundwater depletion, pollution, and clean drinking water availability are growing in urgency and seriousness all around the world. Some even argue that we should boycott World Water Day – that our water problems are too serious to try and confine to a single day.

In January, Brian Richter, director of freshwater strategies at The Nature Conservancy, spelled out four water resolutions through a thought-provoking series of blog posts. One of those resolutions was to better understand and communicate the differences between water use and water consumption. This is a particularly important issue, as there has been a lot of discussion lately about water scarcity, water stress, and the risks associated with them.

So what do ”water use” and “water consumption” mean?

• “Water use” describes the total amount of water withdrawn from its source to be used. Measures of water usage help evaluate the level of demand from industrial, agricultural, and domestic users. For example, a manufacturing plant might require 10,000 gallons of freshwater a day for cooling, running, or cleaning its equipment. Even if the plant returns 95 percent of that water to the watershed, the plant needs all 10,000 gallons to operate.

On February 20, WRI President Andrew Steer participated in event with GreenBiz CEO Joel Makower at the annual GreenBiz summit in New York City. This post builds off that discussion.

Sustainability has become a major business buzzword in recent years. For many, though, it’s still viewed as a philanthropic initiative, disconnected from a company’s core goals, or even a burden that competes with other strategic priorities. That must change.

Fortunately, more leaders are recognizing sustainability risks. At the World Economic Forum in Davos last month, leaders in business, government, academia, and civil society named climate change and water supply as two of the top five global risks facing companies today—and with good reason.

At the World Economic Forum in Davos two weeks ago, I was struck by how often the issue of water risk was raised by business executives. As the global economic turmoil is receding, many CEOs and global leaders are turning to other threats—and water is high on the list. For the second year in a row, water crises were named among the top four global risks at the WEF.

It’s easy to see why. More than 1.2 billion people already face water scarcity. By 2025, two-thirds of the world population will experience water stress. That’s largely due to population increase and climate change, but also behavior patterns: Water use grew twice as fast as population growth in the 20th century. The “food-water-energy nexus” was one of the top four megatrends to watch in the recently released Global Trends 2030 report by the U.S. National Intelligence Council.

Some people say that water is the oil of the 21st Century. If only water were that simple.

Water is very complicated. It’s affected by large-scale issues like climate change and globalization. International commerce moves virtual water (the water it takes to grow or produce a product) from farms in Brazil to grocery stores in China and Egypt.

But water is also inherently local, impacted by site-specific weather, geography, and other environmental and land use conditions. Managing and using water, then, requires understanding it in its full geographic context.

This post was co-authored with Jose Carlos Lombana, co-founder of Sistemas de Captación de Agua Pluvial (SCAP).

This story is part of the “Aqueduct Sneak Peek” series. Aqueduct Sneak Peek provides an early look at how various stakeholders can use Aqueduct’s updated global water risk maps, which will be released in January 2013. Read more posts in this series.

A study by scientists at The Nature Conservancy and other institutions estimates that by 2050, more than 1 billion city dwellers may be living on less than one bathtub’s worth of water a day. While this and other water risks are undeniably troubling, they can be overcome in many cases. With the right data and innovation, entrepreneurs can turn these risks into business opportunities.

This story is part of the “Aqueduct Sneak Peek” series. Aqueduct Sneak Peek provides an early look at the Aqueduct team’s updated global water risk maps, which will be released in January 2013.

New reports and articles are increasingly pointing to water risk as one of the biggest issues associated with climate change, energy production, food security, and human health. In an effort to better understand how and where these water risks are emerging, WRI published the first-ever Aqueduct water risk map two years ago.

This story is part of the “Aqueduct Sneak Peek” series. Aqueduct Sneak Peek provides an early look at the Aqueduct team’s updated global water risk maps, which will be released in January 2013.

The days leading up to Hurricane Sandy’s landfall were a testament to the power of global data systems in helping to understand and manage risks that natural phenomena can create. A vast, worldwide network of weather monitoring stations and sophisticated remote sensing allowed meteorologists to track and predict Sandy’s progress—and give ample warning to those of us in the hurricane’s path.

The map below is one way to visualize the global data network that makes such analysis possible. It shows Integrated Surface Database (ISD) stations, a widely distributed network of weather stations that all report regularly to a centralized hub.

This piece was co-authored by Lijin Zhong, Senior Associate from the WRI China office

The Yellow River has played a critical role in the growth and prosperity of Chinese civilization for thousands of years. But today, the Yellow and the people who depend on it face severe challenges. Stress of limited water resources, pollution, and flooding pose significant risks to communities and businesses that rely on the river. As these stresses grow, China’s water managers and users face the daunting challenge of implementing policies that balance economy, ecology, and community.