Category Archives: Water supply

Drop on the planet: 3 visualizations of Earth’s most precious natural resource

Scarcity of freshwater is a defining feature of the American West, and planet Earth.

Nearly 97% of the world’s H2O is in the oceans. More than two-thirds of the globe’s freshwater is frozen in glaciers and polar ice caps.

Below are a trio of graphics to visualize water on Earth. I’ve found these slides useful for providing context in water-related presentations.

1) The world’s water: drop on a planet

About 70% of the planet’s surface area is covered by water, but the amount is tiny when compared to the Earth’s total volume. The illustration below shows that if you collected all of the planet’s water into a single sphere, it would be 860 miles across. Situated to the right is a 170-mile-wide ball over Kentucky that represents all the fresh liquid water found in the ground, lakes, swamps, and rivers. That miniscule 35-mile-wide dot over Georgia is all the freshwater in lakes and rivers.

Water on Earth graphic
Source: U.S. Geological Survey

2) The water cycle: a closed loop

The diagram below illustrates the water cycle and a critical point: water on Earth is essentially a finite resource and the system is basically a closed one. If you want to be a stickler, it’s not a 100% closed system since there’s a bit of entry and leakage via comets depositing ice and water vapor escaping to space. This graphic also doesn’t show volcanoes emitting steam or water lost to faults on the ocean bed. But the basic point remains: we can reuse water, convert the sea into a potable supply, even try to coax the sky into precipitating with cloud seeding, but we can’t manufacture new water.

U.S. Geological Survey water cycle
Source: U.S. Geological Survey

3) Breaking down the types of water

The graphic below shows that freshwater comprises just 2.5% of the Earth’s total water supply and 69% of that freshwater is locked up in glaciers and icecaps (at least for now). Most of the remaining freshwater is found below our feet as groundwater. Sometimes this subterranean supply is relatively easy to access, but in other locations it may be too deep or costly to extract. Fresh surface water is a rare commodity on this planet. Rivers, for example, account for just 0.006% of all freshwater and 0.0002% of all water found on Earth.
Distribution of water on Earth

We have more slides covering water issues, including supply, demand, quality, infrastructure, and climate change, in our water PowerPoint presentation.


Download Slides: Water on EarthDownload Slides: Water on Earth (5.55 MB pptx)
Download Notes: Water on EarthDownload Notes: Water on Earth (621.38 kB pdf)

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EcoWest’s mission is to analyze, visualize, and share data on environmental trends in the North American West. Please subscribe to our RSS feed, opt-in for email updates, follow us on Twitter, or like us on Facebook.

Plotting “dead pool” and other watersheds for Lake Powell and Lake Mead

The elevations of Lake Powell and Lake Mead, two critical reservoirs on the Colorado River, are like the Dow and S&P 500 for water in the Southwest. These closely watched metrics serve as simple barometers and summaries of how things are going in a fiendishly complex system, be it the U.S. economy or a watershed spread across a quarter-million square miles that provides drinking water for nearly 40 million people.

“Water buffaloes,” the professionals who manage the West’s most precious resource, have been sounding bearish in recent days about Powell and Mead, the nation’s two largest reservoirs by capacity. The past 14 years have been the driest for the Colorado River in more than a century of record keeping. On Friday, federal officials announced they will cut releases from Powell from 8.23 million acre-feet to 7.48 million acre-feet, which would be lowest release since the reservoir was filling in the 1960s.

To track water storage in Powell and Mead, I’ve created a dashboard that plots the lake levels and some important benchmarks. Below are some images from the visualization (click to enlarge). There’s also a PowerPoint presentation you can download at the bottom of the post.

Lake Powell elevation graphic Lake Mead elevation graphic

Elevation benchmarks

The Powell chart plots the daily elevation and the Mead chart illustrates the July 1 level; in the former, you can see the annual ebb and flow. I used two different time scales because that’s how I found the data on the U.S. Bureau of Reclamation’s websites (separate offices manage Powell and Mead).

Capacity shows the elevation when the reservoirs are full. For Powell, raising the spillway gates can slightly increase capacity, but flooding in 1983 did nearly overtop Glen Canyon Dam. When a reservoir is at dead pool, the water level is so low that it cannot drain by gravity through the dam’s outlet works. Hydropower can only be generated when the reservoir is above the minimum power pool. For Mead, which supplies the Las Vegas metro area, the elevation of the Southern Nevada Water Authority’s lower intake is shown.

Our dashboard uses lake elevation, but in our PowerPoint deck we also have some slides showing changes in volume. Each metric tells us different things about the status of the reservoirs, but elevation is easier to visualize. Below is a photo I took last April of Powell’s so-called bathtub ring, which is even more exposed today.

Lake Powell and Glen Canyon Dam
Lake Powell and Glen Canyon Dam, April 2012. Photo by Mitch Tobin.

Satellite imagery shows Powell’s decline

Another way to track the status of these reservoirs is by taking repeat photographs, either on Earth or from space, of the same location. Below are two views of Lake Powell, the first showing 2002 vs. 2003, and the second comparing 2012 vs. 2013, based on NASA satellite imagery.

Lake Powell drought photograph

Lake Powell satellite image drought

The PowerPoint deck that you can download below contains a time series of satellite images of Powell from 1999 to 2013. The contrast between 2012 and 2013 illustrates why federal officials are taking action and cutting releases from the reservoir.

Reservoir levels projected to fall

Looking ahead, federal water managers project that Mead will drop another eight feet in 2014 due to reduced releases from Powell. Below is a graphic from Reclamation that shows Powell is likely to keep falling as well.

Lake Powell elevation projection

Basin susceptible to megadroughts

The outlook for precipitation in the basin over the next few years is uncertain, but one thing we know for sure is that the Colorado River is vulnerable to megadroughts, the likes of which we haven’t seen in modern times. The graphic below, from the U.S. Climate Change Science Program, shows the annual flow of the Colorado River over the past 1,200 years. Scientists used tree rings to estimate the river’s volume before the instrumental record, which is shown as a red line. The arrows point out that the basin has been periodically hit with megadroughts that were worse than the one we’ve been experiencing since 2000.
Colorado River drought tree ring record

Climate change expected to shrink Colorado’s flow

Even without considering climate change, the Colorado River would face a challenging future because the demand for its limited–and capricious–supply is increasing along with the Southwest’s population. But scientists project that even less water will flow down the river in the decades to come due to rising temperatures and altered precipitation patterns. The graphic below, from Reclamation’s recent Basin Study, shows that demand is projected to exceed supply on the river (see our earlier post for more details).

Colorado River historical and projected water use and supply

Data sources

The Bureau of Reclamation provides detailed data on Lake Powell and Lake Mead. I pulled the benchmark levels from this Reclamation presentation, specifically page 15.

If you’re keeping score at home, the capacity of elevation of Powell is listed as 3,700 feet, but during floods the reservoir’s elevation can go slightly above this level by raising the spillway gates. In 1983, Powell reached an all-time high elevation of 3,708.34 feet.

The decision to cut releases from Powell was covered by The Arizona Republic,  National Public Radio, and The Salt Lake Tribune, among others.


Download Slides: Lake Powell and Lake MeadDownload Slides: Lake Powell and Lake Mead (10.23 MB pptx)
Download Notes: Lake Powell and Lake MeadDownload Notes: Lake Powell and Lake Mead (3.13 MB pdf)

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EcoWest’s mission is to analyze, visualize, and share data on environmental trends in the North American West. Please subscribe to our RSS feed, opt-in for email updates, follow us on Twitter, or like us on Facebook.

An interactive map of water risk and stress

The World Resources Institute has developed Aqueduct, an interactive mapping tool that offers a fascinating look at water-related risks and stresses, including projected impacts due to climate change.

Using global data donated by Coca-Cola, one of several heavyweight corporate partners (Goldman Sachs and General Electric founded the Aqueduct Alliance), WRI has analyzed and visualized a dozen water-related risk factors facing businesses, governments, and communities. Below is a view of overall water risk (click to enlarge).

WRI Aqueduct: overall water risk

Elements of water risk

Aqueduct’s water risk model includes a dozen components, as shown in the slide below. The physical quantity risks deal with questions of supply, such as a location’s climate and its susceptibility to drought. The physical quality risks revolve around pollution, such as the protective status of upstream watersheds and how many times river water is re-used. The final category, regulatory and reputational risk, uses proxies, such as the number of threatened amphibians to highlight more fragile ecosystems that may face restrictions on withdrawals. There’s even a measure for media coverage of water issues to indicate where businesses will face greater risks to their public image if they do not manage water sustainably.

WRI Aqueduct water risk framework

In the online atlas, you can examine each of these dozen factors separately and weight the three categories according to the needs of industry groups, including agriculture, semiconductors, and oil and gas. In the screenshot below, I’ve zoomed in on the United States and selected interannual variability (how much the water supply varies year to year). This risk factor is generally much greater in the West than in the East, and especially high in the Southwest. The numbers in circles indicate how many water-related media stories are currently showing up in the map’s built-in news feed.

WRI Aqueduct: example

Background on project

Here’s more about the project from WRI:

Water scarcity is one of the defining issues of the 21st century. In its Global Risks 2013 report, the World Economic Forum identified water supply crises as one of the highest impact and most likely risks facing the planet. With the support of a diverse group of partners, the World Resources Institute built Aqueduct to help companies, investors, governments, and communities better understand where and how water risks are emerging around the world.In January 2013, the World Resources Institute launched the centerpiece of Aqueduct after a three-year development effort: the Water Risk Atlas. The Atlas uses a robust, peer reviewed methodology and the best-available data to create high-resolution, customizable global maps of water risk.

The Aqueduct Water Risk Framework brings together 12  indicators into three categories of water risk and an overall aggregated score. The framework is based on a thorough review of the literature and available global data, and includes several indicators developed exclusively for Aqueduct. It is structured, in particular, to help companies and investors understand indicators of water-related risk to their business, but is intended for all users, including government and civil society to better understand geographic water issues. The Aqueduct Alliance, founded by General Electric and Goldman Sachs, is the network of companies and organizations that support the Aqueduct project. These partners provide resources as well as expertise and perspective to the project.

Mapping water stress

One illuminating feature of the atlas is that it allows you to examine water stress–essentially the imbalance between water supply and demand–under current conditions and three IPCC climate change scenarios.

The map below shows the baseline water stress, which is defined as “the ratio of total annual freshwater withdrawals for the year 2000, relative to expected annual renewable freshwater supply based on 1950-1990 climatic norms.”

WRI aqueduct: baseline water stress

As you would expect, there’s a lot more stress, water-wise, in Phoenix than Portland. The roots of some age-old intrastate water conflicts show up pretty clearly, such as lower water stress in California’s wetter north, but extremely high stress in the drier south. There are similar dividing lines in Colorado: most of the water is on the Western slope, but the bulk of the population is east of Continental Divide along the Front Range.

Projecting climate change impacts

The maps below look ahead to 2095 and depicts projected changes in water stress. I’ve used the IPCC’s optimistic B2 and pessimistic A2 emissions scenarios, which show that higher levels of greenhouse gases will create much more water stress across the country. In the pessimistic scenario, I didn’t find any places in the continental United States where water stress decreased by 2095.

WRI Aqueduct projected change in water stress optimistic scenario

Water stress map

The Aqueduct atlas also has climate change projections for 2025 and 2050. It’s one of many ways you can customize your views of the data and I’d encourage anyone with an interest in water issues to take a few minutes to explore WRI’s useful visualization.

Data sources

WRI provides the data for download on this page. You can also download their framework document and indicator metadata. Below is an embed of their YouTube video explaining how to use the Aqueduct tool.


Download Slides: WRI AqueductDownload Slides: WRI Aqueduct (4.57 MB pptx)
Download Notes: WRI AqueductDownload Notes: WRI Aqueduct (927.33 kB pdf)

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EcoWest’s mission is to analyze, visualize, and share data on environmental trends in the North American West. Please subscribe to our RSS feed, opt-in for email updates, follow us on Twitter, or like us on Facebook.