Environmental Engineering Reference
In-Depth Information
(a)
(b)
Picture 3.2a, b
Satellite photographs of northern part of the Aral Sea in 1973, a Landsat-1 image
(a), and 2000, a Landsat-7 image (b), showing the reduction of water area that was caused by diversion of
feeding rivers to land irrigation projects.
Courtesy of National Aeronautics and Space Association (NASA), 2005.
Besides the massive use of limited water, when irrigation is not properly performed it cre-
ates runoffs. A runoff occurs when the rate of water application exceeds the rate of absorption
by the soil; so water collects on the surface, then follows any slope in the terrain, and forms
stream that takes water away from the intended area. Runoffs waste water and energy, create
erosion by carrying topsoil, and contaminate surroundings with fertilizers and pesticides
(Hansen and Trimmer, 1997). Fortunately, runoffs can be controlled with the proper manage-
ment of irrigation systems.
