After a Drought or Flood you can get an event that gives one of your Governors "Steward of the Land" trait.
You need to not be at war with all tribes (at least one at Truce/Peace), and you need a Governor that is Inquisitive or Productive.
Got it on an [Intelligent] Diplomat courtier governor.
This character can then train other characters to get the trait for 100 civics.
To get the Drought Adept event you need to train a Martial character. It allows a city to make units with the "Drought Adept" promotion.
Got it on a Tactician courtier governor. (probably not needed to be courtier or governor, the city that got the bonus was a different one)
Trait an infantry or mounted unit in that city.