Irrigation has been around since around 6000 BCE. We know it was in modern-day Iraq, and probably in Egypt around that time too. The oldest method of irrigation is surface irrigation, also called flood irrigation. It’s pretty much what the name says it is.
Irrigation was used primarily for watering crops, which helped the transition to agrarian societies. Agrarian societies were able to produce a stable supply of food, and stable supplies of food led to the rise of settlements and eventually cities. Cities led to civilizations.
I don’t think anybody would argue that the mastery of irrigation was not instrumental in shaping the history of our world.