The most definitive answer I can give you is probably. The center of anti-French sentiment and resistance in the 1950s and 60s was in Algeria, home to 8 million Muslim-Algerians and 1 million colons, or long term French settlers.
This forgotten conflict, a rebellion that lasted from 1954 - 62, was as bloody, ugly and brutal as any that have been fought between empire and colony. Bombings and assassinations were used by both the FLN (Muslim rebel group) and the SAO, the Secret Army Organization, formed by hard core right wing former Army General Francoise Sagan, who was both pro-French Algeria and anti-Chares de Gaulle (The President of France, who wanted to let Algeria have independence).
Torture, imprisonment in Algeria of 1 million people in internment and "regrouping" camps, assassination, and every other ugly tactic were used by the French Army, the SAO and the FLN.
With further research I came across some very good articles on this conflict, but found no specific instance or reference to the poisoning of wells. The most likely time this would have happened is when the French Army relocated civilian populations to camps and then wanted to deny water to the rebel or remaining civilians sympathetic to the FLN.