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• “Water use” describes the total amount of water withdrawn from its source to be used.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.

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 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.

With its high reliance on manufacturing, mining, and agriculture, South Africa’s economy runs on fresh water. Recent projections estimate a startling 17 percent gap between water demand and supply in the country by 2030. Even more concerning, the areas most affected, the Gauteng and Vaal River regions, are also the most economically significant: According to the Department of Water Affairs and Forestry, these two areas produce more than 50 percent of South Africa’s wealth and supply more than 80 percent of the country’s electricity requirements (more than 50 percent of all the electricity generated in Africa).

For many companies, water issues have recently migrated from corporations’ social responsibility departments to finance and risk management departments. Companies have been reporting a growing exposure to water-related risks like flooding and pollution, and many have already started to experience water-related business impacts.

This trend prompted WRI’s Markets and Enterprise Program to build a tool to help companies and investors identify water-related risks across their operations or portfolios. The tool, named the Aqueduct Water Risk Atlas, is based on an indicator framework that quantifies and maps different drivers of water risk, otherwise known as the Water Risk Framework. After testing this framework in various regions, WRI recently released its revised version. This updated framework will eventually be used to assess water risks in every part of the world.

The Wei River in west-central China is not just the largest tributary of the Yellow River, but it has also been a critical water source for communities for thousands of years. To manage this important resource, water authorities in China just announced that they plan to invest 6 billion yuan - more than US$950 million - this year to fight floods and pollution in the Wei.

This investment in water management comes after flooding on the Wei killed dozens of people and forced tens of thousands from their homes in the fall of 2011. On top of these terrible human costs come severe economic impacts. According to some estimates, the 2011 flooding cost China more than 6 billion U.S. dollars.

This piece was coauthored by: Joe Rozza, P.E., BCEE, Global Water Resource Sustainability Manager, The Coca-Cola Company; Greg Koch, Managing Director, Global Water Stewardship, The Coca-Cola Company; Jonathan Boright, Research Scientist, ISciences LLC; Nicole Grohoski, Research Analyst, ISciences LLC

The Aqueduct project is an effort to measure and map water related risks being developed by the World Resources Institute with the support of an alliance founded by General Electric and Goldman Sachs. As part of this effort, the Aqueduct team convened its hydrological modeling partner ISciences and experts from The Coca-Cola Company to develop and analyze a set of maps for the Bonn2011 Nexus conference that illustrate the complex relationships between water, food, and energy worldwide (see below).

Why focus on the water-food-energy nexus? Like water, food and energy are basic necessities of life that help support robust economies and stable political systems. Agriculture and power generation, moreover, account for the majority of water withdrawals in most developed countries.