Impact of Climate Change and Land Use on the Southwestern United States

Human impacts on the landscape


Imperial Valley, California

by Robb Campbell, U.S. Geological Survey

The Salton Sea first became a lake in 1891; it covers approximately 930 sq km and lies 70 meters below sea level. Having no outlet, the Salton Sea is being contaminated by runoff water containing a mixture of agricultural, industrial and municipal wastes. Approximately four million tons of salt are transported to the lake each year. The Mexican city of Mexicali and the U.S. city of El Centro grew significantly between 1973 and 1992. The U.S./Mexico border is clearly visible in the Landsat images; agricultural practices such as field size, use of irrigation, and the use of herbicides and pesticides, create different field colors and patterns on the two sides of the border.

1973 image (23 May / 9 June, Landsat 1 MSS, RGB = infrared red green)

1992 image (30 June, Landsat 4 MSS, RGB = infrared red green)

Landsat scenes

Note: The two 1973 scenes are mosaicked together.

LM1041037007316090 9 June 19734137MSS
LM104203700731439023 May 19734237MSS
LM403903700921829030 June 19923937MSS

Map of the region

From 1:1M USGS map Los Angeles (International Map of the World, 1947)

Link to USGS home page

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