Resembling a work of modern art, variegated green crop circles cover what was once shortgrass prairie in southwestern Kansas. The most common crops in this region-Finney County-are corn, wheat, and sorghum. Each of these crops was at a different point of development when the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) captured this image on June 24, 2001, accounting for the varying shades of green and yellow. Healthy, growing crops are green. Corn would be growing into leafy stalks by late June. Sorghum, which resembles corn, grows more slowly and would be much smaller and therefore, possibly paler. Wheat is a brilliant gold as harvest occurs in June. Fields of brown have been recently harvested and plowed under or lie fallow for the year.
Like crops throughout large sections of the U.S. Midwest, these crops are partly fed by water from the Ogallala Aquifer, a giant layer of underground water. The rivers and streams that initially fed the aquifer have long since disappeared in the geologic development of the West after the last ice age. Water now takes a long time to trickle down through the soil to recharge the aquifer, though the rate varies from region to region. Like a bank account, if more water is taken from this underground bank than is deposited into it, it could run dry. For this reason, efforts are being made to conserve the water of the Ogallala Aquifer.Image Credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team