Tag Archives: lawrence livermore national laboratory

Flow diagrams of U.S. and Western carbon emissions

The United States emits around 5.6 billion metric tons of carbon dioxide equivalent (CO2e) each year. That’s roughly the annual CO2 exhaust of 1.2 billion cars, according to the U.S. EPA’s Greenhouse Gas (GHG) equivalency calculator, and it’s nearly 20 percent of annual global GHG emissions.

U.S. and Western carbon flow diagrams from EcoWest on Vimeo.
Flow diagrams from the Lawrence Livermore National Laboratory provide informative visual summaries of the nation’s carbon emissions from generation to end use. These graphics, also known as Sankey diagrams, show how many GHGs originate from the burning of fuels and how many GHGs are attributable to different economic sectors. Think of the left side of the flow as the supply side, and the right as the demand side. In this deck, I’ve also compiled slides representing GHG emissions in the 11 Western states, which show some interesting patterns in GHG emissions from origin to end use.

Data on GHG emissions is only available at the national level. To understand state-by-state differences, Lawrence Livermore uses state-level energy use data to estimate the flow of GHGs. The U.S. Department of Energy’s Energy Information Administration compiles such energy use data in the State Energy Data System (SEDS).

Sankey carbon

U.S. carbon emissions are generated by burning coal, natural gas, and petroleum products (gasoline, diesel, etc.); roughly 35%, 23%, and 42% of 2010 emissions, respectively. The carbon flows in individual states vary widely depending on state energy portfolios. End uses differ according to what industries predominate and population levels. Some of the patterns that jump out:

  • California, Idaho, Oregon, and Washington are less coal-dependent and more petroleum dependent.
  • Natural gas accounts for a higher portion of carbon emissions in states like Nevada and Oregon.
  • Petroleum accounts for a lower portion of carbon emissions in Colorado and Wyoming.

Comparing Washington to Wyoming demonstrates how end use differs by state. Energy generation accounts for the bulk of carbon emissions in Wyoming, but the transportation and industrial sectors dominate in Washington. Wyoming is a major energy exporter to other states, while Washington relies heavily on hydropower, which does is essentially carbon-free.

When examining these slides, it’s important to remember that the size of the rectangles and the lines between them are not comparable from state to state. They show, within a state, where GHGs originate and terminate in various uses.

Lawrence Livermore also produces similar graphics for energy and water, and in another post, we provide a little background on Sankey diagrams, which are great tools for visualizing how commodities flow through systems.


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Flow diagrams of U.S. and Western water use

Americans use an average of 410 billion gallons of water per day. Where does all that water come from and where does it go?

Flow diagrams from the Lawrence Livermore National Laboratory provide excellent summaries of the nation’s water use. These graphics, also known as Sankey diagrams, show how much we pump from groundwater aquifers, how many gallons of surface water we divert, and which economic sectors use the most water.

In this slide deck (download links at bottom of post), I’ve pulled together the flow diagrams for the 11 Western states, which show some interesting regional patterns in water use.

Flow diagrams of U.S. and Western water use from EcoWest on Vimeo.

Diagrams visualize commodity flows

Lawrence Livermore produces similar graphics for energy and carbon dioxide. In another post, I provide a little background on Sankey diagrams, which are a great tool for visualizing how a commodity flows through a system.

Data for the water diagrams come from the U.S. Geological Survey, which publishes a report every five years summarizing the nation’s water use (the latest year available is 2005).

The flow diagrams segment water sources into four main categories: fresh surface water, saline surface water, fresh groundwater, and saline (brackish) groundwater. Lawrence Livermore summarizes national-level water use this way:

Fresh surface-water, from lakes and rivers, is used at large scale in every sector of the economy. Saline surface water, primarily ocean water, is mostly used for once-through thermoelectric cooling, although some ocean water is used for industrial cooling and a small but growing amount of ocean water is being desalinated for public consumption. Significant quantities of fresh groundwater are used in irrigation and fresh groundwater plays an important role in both public supply as well as self-supplied domestic water consumption. Brackish groundwater is the most difficult water resource to use and is therefore primarily used in the mining sector and in power production (often in geothermal power plants).

Western states vary widely

The state-level slides reveal that water is managed very differently across the West, with some residents heavily dependent on surface water and others more reliant on groundwater. In Montana, Utah, and Wyoming, saline groundwater is an important source for mining and industry, while in Idaho and Oregon there’s a fair amount of fresh water devoted to aquaculture.

Across the region, the water delivered to homes and businesses is just a fraction of what’s devoted to growing crops. Consider the arid state of Arizona, where discussions about water tend to focus on the state’s growing cities. In reality, the graphic below (click to enlarge) shows that farming totally dominates water consumption in Arizona.

Arizona water flow

When examining these slides, it’s important to remember that the size of the rectangles and the connecting lines are not comparable from state to state. Instead, they show the proportions of surface water and groundwater that are directed to various uses within each state.

Lawrence Livermore also offers this caveat:

Water use data is notoriously hard to compile. Accounting policies vary between different water management districts and water use is not metered in the same way that higher-priced commodities are sold. Quantifying water use by location and sector requires substantial estimation.Water disposition is even more difficult to quantify. While the quality of wastewater discharge is measured regularly for environmental purposes, the total quantity of wastewater is not carefully monitored, especially when that wastewater already meets environmental regulations for discharge.

Despite these drawbacks, I’ve found these diagrams to be super-helpful in understanding Western and national water-use patterns. Once the U.S. Geological Survey releases data from the 2010 report, which isn’t expected until 2014, it’ll be interesting to see if there have been any significant shifts in water use.


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.

Go with the flow: Sankey diagrams illustrate energy economy

Energy flows through everything, so it’s only fitting to use flow charts to depict our complex energy economy.

Since the early 1970s, the Lawrence Livermore National Laboratory has been producing such graphics, not only for energy, but also for water and carbon dioxide. Technically known as Sankey diagrams, these data visualizations summarize flows through a system by varying the width of lines according to the magnitude of the commodity in question.

In this deck of slides, I offer up some of Sankey diagrams that illustrate energy trends in the United States and Western states. Looking at these visualizations over time shows that fossil fuels continue to dominate the nation’s energy mix, but renewable sources are making some headway. In the West, some inland states rely almost exclusively on coal to generate electricity, but other states use significant quantities of natural gas, wind, and nuclear power. Overall, petroleum in the transportation sector accounts for the greatest share of our energy flows.

History of diagram

Matthew Henry Phineas Riall Sankey
Matthew Henry Phineas Riall Sankey. Source: Wikipedia

Sankey diagrams are named after Matthew Henry Phineas Riall Sankey, an Irish Captain who used the graphic in a 1898 publication on steam engines. Since then, Sankey’s diagrams have won a dedicated following among data visualization nerds. There’s even an entire blog devoted to the graphic, which boasts in its tagline that “a Sankey diagram says more than 1,000 pie charts.” The blog has a good overview of software tools that create Sankey diagrams here.

One of the earliest and most famous examples of the form illustrates Napoleon’s disastrous Russian campaign in the early 19th century. Created by Charles Joseph Minard, a French civil engineer, the graphic (technically, a flow map) depicts the army’s movement across Europe and shows how their ranks were reduced from 422,000 troops in June 1812, when they invaded Russia, to just 10,000, when the remnants of the force staggered back into Poland after retreating through a brutal winter.

Data visualization guru Edward Tufte, whose undergraduate political science class helped get me interested in graphics and data analysis more than two decades ago, calls it “probably the best statistical graphic ever drawn.” Besides showing the declining troop totals, the graphic details the army’s location and direction over time, as well as the temperature.

Minard's flow map
Minard’s famous flow map. Source: Wikipedia

Significant shifts in energy flows

LLNL’s latest energy diagram, released in October 2012, depicts 2011 data and illustrates some major changes in the nation’s energy sector. As the lab noted in its press release, “Americans used less energy in 2011 than in the previous year due mainly to a shift to higher-efficiency energy technologies in the transportation and residential sectors.”

The largest increase in energy production was in the wind sector; hydropower also grew due to a wet winter in the West. Even so, the nation’s energy flows are still dominated by coal, natural gas, and petroleum. “Sustained low natural gas prices have prompted a shift from coal to gas in the electricity generating sector,” said A.J. Simon, an energy systems analyst at the lab. “Sustained high oil prices have likely driven the decline in oil use over the past 5 years as people choose to drive less and purchase automobiles that get more miles per gallon.”

LLNL energy Sankey

Energy use varies widely in West

Among Western states, the Sankey diagrams show some clear patterns. States like Wyoming, Colorado, New Mexico, Montana, and Utah rely heavily on coal for their electricity production, in some cases exporting that power to other states. Coal may be king for electricity generation in many states in the intermountain West, but it’s hydropower that dominates power portfolios in the Pacific Northwest: Washington, Oregon, and Idaho get the bulk of their electricity from dams. Other states have more diversified portfolios; Arizona, shown below, relies on a mix of coal (40%), nuclear (27%), natural gas (26%), and hydropower (6%). But not much solar for a pretty sunny state.

Arizona Sankey energy

In all of the energy diagrams, you’ll notice that a significant share of energy is “rejected.” A good example of rejected energy is waste heat from power plants. The greater the percentage of rejected energy, the less efficient the system. It’s worth noting that the state-level data is from 2008, three years older that the national data, and the U.S. energy economy has undergone some major shifts since then, including a shift from coal to natural gas and growing competitiveness of wind power.

Long-standing data source

The Lawrence Livermore National Laboratory has published flow charts of energy, water, and carbon dioxide since the early 1970s, sometimes going down to the level of individual states. Here’s how the lab describes the graphics and their creation:

Flow charts are valuable as single‐page references that contain quantitative data about resource, commodity and byproduct flows in a graphical form that also conveys structural information about the system that manages those flows. Recent advances in the automation of Sankey Diagram generation have made it possible to produce a consistent set of state‐level energy flowcharts. A computer program reads SEDS [State Energy Data System] data, performs a set of calculations and re‐sizes and re‐labels the flows in the figure. Human interaction is required only to reconcile instances where graphical elements overlap.

Other versions

The U.S. Department of Energy’s Office of Science offers similar diagrams, including one that embeds some interesting factoids and imagery. I’ve included them in the deck as well. Here’s how the agency summarizes its flow graphics:

Oil provided the largest share of the 98 quads of primary energy consumed, and most of it was used for transportation. Consumption of natural gas, the nation’s second largest energy source, is split three ways—electricity generation, industrial processing, and residential and commercial uses (mostly for heating). Coal, our third largest source, is used almost exclusively for electricity. Nuclear energy and renewables each meet less than 10% of U.S. energy demand.

The International Energy Agency has also produced a poster-sized Sankey diagram depicting world energy flows (there’s a PDF available, but the text is microscopic).

In a future post, I’ll take a closer look at Sankey diagrams that visualize water flows. In the meantime, I’d be curious to hear what others think about these graphical tools and any insights they reveal about the energy challenges we face.


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.