Landsat in Arizona: Colorado River Water, Wildfire Fuels, and a Hotter Phoenix

Arizona is a land of deep gorges, high mountains, broad plains and lofty mesas — above all the Grand Canyon, one of the seven natural wonders of the world, cut by the Colorado River through northern Arizona to expose nearly two billion years of Earth's history.

But the landscape is changing. Arizonans face more extreme heat and drought from climate change. Amid a western drought, Lake Mead, one of the state's main water sources, fell to a record low in June 2021, and climate change is making dust storms and heat waves more common, with higher risks to health, according to the Centers for Disease Control and Prevention.

Landsat — whose Landsat 8 and Landsat 9 satellites were built in Arizona — helps track these changes in three key areas.

Water

Over the past couple of decades, climate change and a growing population's water use have pushed the Colorado River Basin's reservoirs to critically low levels. A 2019 law lets the Interior Secretary, through the Bureau of Reclamation, oversee a seven-state agreement — the Colorado River Drought Contingency Plan — to cut water use through 2026 and protect the river's two largest reservoirs, Lake Powell and Lake Mead.

In the Lower Colorado River Basin, which includes most of Arizona, Landsat is used to model water consumption — water evaporating from soil and transpired by plants. That should shed light on the lower basin's tributaries, where up to 70 percent of water goes to irrigation. The Landsat archive can also give consistent, field-by-field histories of water use over the past 40 years.

The Antelope Point public launch ramp on Lake Powell, June 2021: closed to motorboats because of the low water, though kayakers could still use it. National Park Service

Wildfire

Normalized Difference Vegetation Index (NDVI) data from Landsat, current and historical, show how green vegetation is and where fire fuels exist. That helps fire modelers predict where a fire will go, how hot and how fast it will burn, and where to send firefighters. LANDFIRE's Modeling Dynamic Fuels with an Index System uses Landsat to map the condition of annual grasses across the Southwest, Arizona included, in season.

Heat in Phoenix

Phoenix is one of the warmest cities in the country, and excessive heat there has been a major concern for decades — harming health and comfort, straining water and energy use, and worsening air quality. As the metro area grows, surface and air temperatures keep rising. Landsat can show planners how adding trees, grass and shrubs in growing areas can lower temperatures and water use.

Phoenix in a Landsat 8 image of January 13, 2020. U.S. Geological Survey

Landsat for the nation

The USGS National Land Imaging Program supplies satellite imagery and other remote sensing and geospatial data to government, business, universities and the public, with worldwide access to Landsat through the USGS Earth Resources Observation and Science (EROS) Center, which the program funds.

• Landsat is the most widely used land remote sensing source among federal civilian agencies, informing everyday decisions on land, water and resources that protect life and property, safeguard the environment, advance science and education, support climate resilience and grow the economy.
• Businesses and commercial imaging firms build products and services on it.
• A 2017 USGS study put Landsat's annual economic benefit in the United States at $2.06 billion, far above its cost.
• Landsat 8 and 9 cover Earth's land every 8 days. NASA and the USGS are reviewing a joint Architecture Study Team's findings to shape Landsat Next, extending the 50-year record — the world's longest time series of Earth's land surface.
• Consistent data offered at no cost let users study long-term trends, and cloud computing puts Landsat into decision tools across government and industry — used every day, like global positioning systems and weather data.

Sources

Based on Arizona and Landsat, U.S. Geological Survey Fact Sheet 2021–3039, USGS Publications Warehouse, citing the National Park Service (2019), the U.S. Geological Survey (2019), LANDFIRE (2021), Xian and Shi (2019) and Straub and others (2019); a work of the United States government in the public domain. The LANDFIRE detail is from the fact sheet's figure caption.