Except the impact was totally predicted. Climate change, with more total energy in the atmosphere, increases the occurrence of extreme weather events - the lengths and severity of droughts, but also the severity of extreme flooding. The best example I've seen of this is portions of Australia: would have to search to find the source but a great quote was that over a ten or twenty year span they had totally average rainfall - it was just distributed with 9 years or something of extreme drought followed by intense floods.

It has long been known that drought is a major problem for the Panama Canal, and that climate change will increase the severity and occurrences of droughts. None of this is unexpected.