The University of Arizona

Background | CLIMAS


Over the centuries, drought has uprooted sophisticated cultures residing in what we now call the southwestern United States. For example, the ancestors of the Pueblo people, the Anasazi, abandoned dozens of multistoried structures in the Four Corners area of the Southwest during a “Great Drought” that stretched across the turn of the 13th Century.

Tree-ring records and other natural archives reveal that the Southwest has regularly seen dry periods lasting as long as 10-20 years. While the 20th century did not see decade-long "megadroughts," severe drought in the early 1900s and in the 1950s caused devastating impacts on people in Arizona and New Mexico.

According to some climate experts, the most recent drought began in parts of the Southwest as early as 1996. Dry conditions have been worsening since that time; by the summer of 2002 most of Arizona and New Mexico were considered to be in "extreme" drought. Arizona was declared a drought disaster area on May 17, 2002 by U.S. Secretary of Agriculture Ann M. Veneman. The National Climatic Data Center observed in June 2002 that the Rio Grande’s streamflow in New Mexico was lower than it had ever been before based on the 102-year instrumental record.

People living in rural areas have suffered the most from dwindling water supplies, but as the drought continues larger cities may expect water shortages as well. Drought has already had devastating impacts on southwestern ecosystems—from large wildfires to the die-off of ponderosa pine and piñon juniper forests due to combined stress of insect infestation and lack of moisture.

El Niño as savior?

While the drought was worsening in the summer of 2002, forecasters began to notice unusually high sea surface temperatures in the eastern Pacific, the telltale sign of El Niño’s arrival. This climatic pattern is associated with greater rainfall in the southwestern United States and northwestern Mexico.

However, even a strong El Niño only increases the probability of precipitation in the Southwest—it does not guarantee it—so southwestern climatologists do not view El Niño as a panacea for the drought.