The Colorado River is the principal source of water for irrigation and domestic use in Arizona, southern California, and southern Nevada. The BOR accounts for water use by each state and individual water user, and verifies fallowed lands for conservation programs and other water management analysis needs, by routinely monitoring more than 3.5 million acres of agriculture and riparian vegetation along the Lower Colorado River from Hoover Dam south to the international border with Mexico. Multispectral satellite images are analyzed in combination with other spatial data in a Geographic Information Systems (GIS ) environment to generate information regarding crop and riparian types, acreages, and associated water use estimates. These data and information assist the BOR in meeting its U.S. Supreme Court mandate to provide detailed and accurate records of diversions, return flows, and consumptive use estimates of water diverted from the mainstream of the Lower Colorado River.
http://www.usbr.gov/lc/region/g4000/wtracct.html
Areas of monitoring on the Lower Colorado River shown in red (agriculture) and green (riparian).
Landsat color infrared satellite image with digitized agricultural field borders in the Imperial Irrigation District, California.