Earthshots: Satellite images of environmental change – Lake Urmia, Iran

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Abstract

Earthshots introduces remote sensing by showing examples of how environmental changes look from space.

Lake Urmia in Iran is another closed basin lake that has been shrinking. Continuous declines in water flowing into the lake have caused a general decline in its surface area since 1995. Satellite imagery of the lake only goes back to the 1960s. But according to historical records, lake levels in 2008 reached their lowest point than any in the past 100 years. New Landsat imagery shows the lake at even lower levels, well below the long-term average. (Lake levels are also monitored by the USDA Foreign Agricultural Service.)

Water only enters Lake Urmia via rainfall and runoff from rivers flowing into it. As a closed basin lake, its water levels fluctuate with changes in rainfall. Once water reaches the lake, it only leaves via evaporation. When the water that flows into the lake is diverted for human uses, those dynamics are prone to big changes.

The lake’s southern basin is shallower than its northern basin, so recent images show the water disappearing from the southern basin first. These Landsat images use the shortwave-infrared, near-infrared, and green wavelengths of light. Because water absorbs infrared light, water (dark blue to black) contrasts with the surrounding land areas. As the water becomes shallower, light is reflected off of the lakebed in shades of light blue. Lighter blue and bright areas immediately surrounding the lake are where the receding shoreline has exposed the lake bottom.

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Additional publication details

Publication type Dataset
Publication Subtype Website
Title Earthshots: Satellite images of environmental change – Lake Urmia, Iran
Year Published 2015
Language English
Publisher U.S. Geological Survey
Contributing office(s) Earth Resources Observation and Science (EROS) Center
Description HTML Document
Country Iran
Other Geospatial Lake Urmia
Online Only (Y/N) N
Additional Online Files (Y/N) N