Earthshots: Satellite Images of Environmental Change

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» San Antonio, Texas, USA

These images show the metropolitan area of San Antonio, Texas. According to the U.S. Census Bureau, the population of the San Antonio metropolitan area was 863,669 in 1970. By 1990, the population had grown to 1.41 million. That growth continued, with increases to 1.71 million in 2000 and 2.14 million in 2010. The population change from 1990 to 2010 is a 25% increase, and in 2010, San Antonio ranked 25th in the country in population.

Click the other tabs to see the changes over time near Randolph Air Force Base in the northeast part of the city, near the reservoirs southeast of the city, and the pronounced urban/suburban expansion west of the city.

Map of the featured area.

Randolph Air Force Base is visible as two white strips northeast of the city. The base’s streets were laid out in a series of concentric circles, with the runways along the east and west sides. This pattern can be seen in the series of Landsat images. Randolph Field was dedicated on June 20, 1930, so there is not much change to see to the base itself. What changes is the amount of residential buildup surrounding the base, development creeping in from the southwest and spilling over the north side of the base.

Street patterns in residential areas are clearer in some images than in others. As trees in these neighborhoods mature, they begin to cover the streets, so you will see this progression in these images.

Calaveras Lake and Victor Braunig Lake are artificial lakes that provide cooling water for nearby power plants. The lakes are also popular fishing and boating destinations. Two of the power plants can be seen in the images, in the crooks of the two larger lakes (Calaveras is on the right).

By contrast, Mitchell Lake, west of Braunig Lake, is a natural lake. The shallow lake is on a migratory bird route and is used by over 300 species as a resting point. Because it is shallower than Braunig Lake and Calaveras Lake (average depth less than 8 feet), Mitchell Lake appears slightly blue in some images.

You’ll also notice a major change just west of Mitchell Lake between the 2002 and 2013 images. The smattering of white along the western edge of the 2013 image is Toyota Motor Manufacturing Texas, a manufacturing plant for Toyota pickup trucks. The plant began operations in 2006.

Pronounced urban/suburban expansion is visible on the west edge of the city. The main outer loop highway visible in all images is 1604. New residential areas push westward to expand beyond this outer loop into the surrounding forests. Also noticeable is the addition of Highway 151, which runs from east to west. New retail development can be seen as the small bright white shapes just north of where this highway intersects with 1604. Can you also spot where a golf course was built in this time period? How about the progression of other new roadways?


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