Managing Western water from space

Over the last 40 years, images from space have shown us a lot about the changing West. Data beamed down from NASA’s Landsat satellites have revealed how cities like Las Vegas are oozing into the desert, how bark beetles are spreading through and killing Colorado’s forests and how ecosystems recover from wildfires.

Besides wowing us with beautiful images of our planet, Landsat is fundamentally a natural-resources satellite, since 80 percent of its data relates to natural resource studies and management. On Monday, NASA launched its eighth Landsat orbiter just in time to keep the data flowing. (Last year, the agency retired Landsat 5, leaving only the ailing Landsat 7 to monitor the world’s landscapes through 2012.)

The Landsat program has been a workhorse for agriculture and water management. When funding for Landsat 8 was in the works during the mid-to-late 2000s, the budget omitted a pricy thermal infrared (temperature) sensor used to track water consumption. Western politicians like then-Colorado Senator Ken Salazar and Idaho Senator Mike Crapo, along with the Western Governors Association and engineers and water resources experts from Western states, quickly jumped in to argue the importance of the thermal sensor and ask Congress to reconsider.

In a 2006 letter to the White House Office of Science and Technology, Wyoming state engineer Patrick Tyrrell explained that Landsat’s thermal sensor is necessary for Wyoming to uphold its end of the Colorado River Compact. It helps the state estimate how much water it’s used in a given year, and whether it’s sending enough downstream to meet the requirements of other states. Based on such arguments, Congress relented and funded the sensor in 2009.

As Wyoming’s case demonstrates, Landsat provides an important window into the past that is particularly useful in battles over water rights. “There’s only one time machine, and that’s Landsat data,” says Tony Morse, an independent remote-sensing consultant retired from the Idaho Department of Water Resources. “Remarkably, going for a ride in that time machine is free.” It wasn’t always that way. Landsat was privatized from 1984 until 2001, and eventually a single image cost around $4,000, pricing most users out of the market. Applications for Landsat really took off when the data became publicly available through the USGS, explains Morse.

Idaho was one of the first states to rely on Landsat for water management. In 2000, state officials began using data from the thermal infrared sensor to map evaporation and water loss through plants and from individual agricultural fields. That information has been key in helping settle water rights disputes and has even been used as evidence in a case before Idaho’s Supreme Court. Other applications include using Landsat to ensure that salmon have enough river water and to provide input for irrigation planning models. “The free data have supported much better decision-making about a publicly-held resource,” says Morse, who was part of developing Idaho’s water-mapping tool that is now applied throughout the West.

Landsat 8 and its thermal sensor will provide at least five more years of data, and while it won’t keep Westerners from arguing over water, it will continue to ensure that the debate is at least based on some objective data. “How are we going to allocate water in an intelligent way?” says Morse. “Well I can’t tell you that, but I can tell you with great assurance that we can’t manage what we cannot measure.”

Sarah Jane Keller is an intern at High Country News.

Landsat image of Lake Powell in April 2012 courtesy of NASA Earth Observatory. Landsat-derived Idaho irrigation image courtesy of the University of Idaho.