From Paul Kedrosky’s Infectious Greed:

500-year history of water flows in the Colorado River

A few things to note:
1) the levels at which the southwestern states draw water was determined during one of the wettest periods during the last 500 years, meaning that each state’s allocation will, by definition, be too high.
2) The mean for this century is higher than the 500-year average due primarily to this wet period.
3) Note that the final blue spike falls roughly in the last 25 years, meaning that those of you who are my age or younger have a memory of water levels that are WAY higher than average.
4) The “drought” we are currently in actually represents a Colorado River level that is roughly at the 500-year average, meaning that we should permanently consume water at this level (if not lower) and not just reduce our consumption for a couple years to “get through it.”