A pivot irrigation system creates a distinctive pattern on farmland in Colorado’s San Luis Valley.
The
high-altitude valley—sitting 7,000 feet (2,130 meters) above sea
level—is arid but situated atop shallow groundwater sources that rise
to form surface springs, lakes, and marshlands. Those waters, recharged
by seasonal snowmelt from the surrounding mountains
, have been used to
extensively irrigate crops in the area since the late 19th century.