What did irrigation do to develop civilizations?

The invention of agriculture was arguably the most important invention in human history in terms of its impact on societal growth. Prior to agriculture, humans practiced horticulture, or simple farming, which basically involved caring for plants and trees—removing weeds, pruning, and so on. Agriculture is large-scale and involves the purposeful planting and organization of farms for optimal growth. Without agriculture, societies could not produce enough food to sustain large populations. Thus, it was because of agriculture that small-scale societies developed into large-scale societies.
But as farms must be purposefully planned, they need to be well taken care of to ensure their success. Above all else, a successful farm must receive plenty of water. A small garden can be cared for using a watering can. But a farm is far too big to have people moving around with watering cans as it would take a lot of people constantly moving about, watering plants, retrieving water, and repeating the cycle. A more efficient method is to bring the water directly to the plants through an irrigation ditch. A farmer can simply open a valve or raise a gate holding back water and then supply an entire field, thereby ensuring that all plants received water.
Irrigation also allowed for people to reclaim land that would otherwise be incapable of growing plants. The Egyptians were masters of land reclamation and irrigated farms on what was previously desert on either side of the Nile River. Their agricultural projects produced enough food to feed an entire civilization. Similar projects are done today all over the world and have been essential for feeding (and growing) the world's population.
So just as agriculture was a necessary element for societal growth and the development of civilizations, irrigation was the key element in ensuring agricultural success. You could not have one without the other.
http://waterhistory.org/histories/nile/t1.html

https://www.bighistoryproject.com/media/bhp-assets/U7_Agriculture_and_Civilization.pdf