A new study led by the Bureau of Reclamation found an extreme drought impacted the upper Colorado River Basin almost 2,000 years ago. 

The study published in Geophysical Research Letters found that a drought in the second century was unmatched even by the current severe drought or ones previously identified.

The ongoing drought in the Colorado River has shown only 84% of the average water flow. But the second-century drought was worse, as it saw only 68% of the average flow.

University of Arizona professor Connie Woodhouse, the study's co-author, says in a press release that paleoclimatic data from lakes, bogs and caves document the extreme drought. 

It is hoped that water managers will be able to plan for future droughts better by studying those from the past.