IRRIGATED LANDS CAN BE ESTIMATED 
ACCURATELY BY PHOTO INTERPRETATION 
OF LANDSAT: COLOR COMPOSITES 
Robert C. Heller 
Research Professor 
College of Forestry, Wildlife and Range Sciences 
University of Idaho 
Moscow, Idaho, USA 
Kim A. Johnson 
Research Analyst 
Idaho Department of Water Resources 
Boise, Idaho, USA 
INTRODUCTION 
During the peak of crop growth in irrigated fields, near infrared 
reflectance of plant growth (0.7 to 1.1 um) is very high. During this 
growing period, on LANDSAT color infrared (CIR) images produced by the 
EROS Data Center or NASA's Goddard Space Flight Center, irrigated 
croplands show up as geometrically regular shapes in strong reddish 
hues. Since most irrigated lands occur in arid to semi-arid areas of 
the world, the contrast between irrigated cropland and surrounding dry 
lands is great and the two land uses are easily separable on LANDSAT 
color infrared transparencies. 
A good part of southern Idaho is considered high desert and native 
vegetation consists of sagebrush species (Artemisia spp.) and various 
rangeland grasses. However, there is an adequate source of water for 
irrigation purposes from the Snake River and the Snake River aquifer. 
Flood irrigation has been practiced for at least 80 years in some parts 
of the state. More recently, sprinkler irrigation methods (especially 
central pivot installations) have been used in developing new fields for 
agriculture. Because the rate of growth of newly installed irrigation 
systems is difficult and expensive to assess by, ground records and 
visits, the Idaho Department of Water Resources— was interested in 
trying new techniques to help them inventory irrigated lands. These 
data in turn would be used to determine water demand from existing known 
water sources and permit more realistic planning for future uses of 
available supplies. 
  
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~The study described herein was done cooperatively and partially funded 
by the Idaho Department of Water Resources, Boise, Idaho.