 emerge from the trees along the inlet. Eight years after the disaster, in 1972, the wooded shoreline has vanished, the bluffs now submerged in a sediment band created by the cataclysmic actions of the temblor. Yet extensive new development shows that Anchorage continued to expand in this area.
These are just two of the 6.5 million aerial photographs that span the last 80 years and are available on the USGS EarthExplorer Web site. Along with millions of other data files in the EROS archive that have been acquired from satellites, airborne radar, and the U.S. space program, these aerial photographs tell an important and compelling story about land cover that is ever changing, both in the United States and around the globe.
Landsat Reveals Water Use Dynamics in the San Joaquin Valley March 14, 2016
California’s San Joaquin Valley is one of the world’s most productive agricultural regions. Much of that productivity depends on the availability of water for irrigation. Recent prolonged droughts in California have underscored the importance of accurately monitoring changes and trends in water use in order to make well-informed water management decisions.
Scientists with the USGS Earth Resources Observation and Science (EROS) Center used Landsat images to quantify water use in the San Joaquin Valley over a 30-year period. A first step was to determine evapotranspiration (ET), which is water transpired by plants into the atmosphere as well as water that evaporates from the surrounding soil. ET can be used as a measure of water usage across a landscape. The scientists employed a computer model that incorporates Landsat imagery, including the Landsat 8 thermal band, along with climate data to estimate ET for every Landsat scene of the Valley from 1984 to 2014.
The team then integrated the ET results with precipitation and runoff data to create maps that reveal historical trends in water use and availability on irrigated basins in the Valley over the 30-year time period. Detailed enough to show individual fields, the maps depict water use (in millimeters) for a given day or an entire growing season, and, when combined with crop data, can also reveal which crops are using the most, or least, water.
The two maps above show seasonal water use in the San Joaquin Valley in 1990 (left) and 2014 (right). Color coding indicates how irrigation patterns changed over time. Notice, for example, that water use intensified in many places (increase in blue areas) and some irrigated lands (green in 1990) transitioned out of agricultural production (reddish brown) by 2014.
Landsat data are free and easily accessible at http://earthexplorer.usgs.gov/. This research approach can be replicated to produce similar water use maps for other locations across the United States. These maps can help farmers, water management agencies, and rural development planners balance irrigation practices and crop choices with precious water resources.
Sometimes the destructive nature of wildland fires lies beyond the flames. It reveals itself in what is left behind—scorched mountainsides with no trees to stop rain-driven mudslides or dangerous debris flows. When such potential exists, the Shortwave Infrared (SWIR) bands on the sensors aboard the Landsat satellites help to identify those possibilities quickly.
The SWIR bands measure diminished moisture content in soil and vegetation. When SWIR band 7 is paired with Landsat’s Near-Infrared (NIR) band 5, which is highly sensitive to growing vegetation, the two produce vivid, accurate images of burn scars. That information is useful to post-fire responders who must act quickly to stabilize burn areas and address potential risks to people, property, and communities nearby.
Landsat 8 helped map destruction caused by the Cougar Creek fire 75 miles northeast of Portland, Oregon, in mid-August 2015. At left is a pre-fire image of Mount Adams in Washington. Snow appears cyan on its peak. In the middle is a post-fire image where the previous green vegetation south and east of the mountain is now charred and appears in shades of re