- "The man who has grit enough to bring about the afforestation or the irrigation of a country is not less worthy of honor than its conqueror."
- –Sir John Thomson
- "Thousands have lived without love, not one without water."
- –W. H. Auden
Irrigation is the first agricultural technology beyond basic farming. With it, your civilization learns how to use water to boost crops, and how to manipulate large quantities of water in general. The tech allows your civilization to cultivate more advanced crops, via the Plantation improvement. It also allows harvesting of the Bananas bonus resource and clearing of Marshes.
Irrigation is important mainly because it unlocks the great Plantation improvement - a major Gold booster in the beginning of the game, which also allows access to a wealth of Luxury Resources, so sooner or later you will need to research it. However, the Plantation can only be built on specific Luxuries, and if you don't have them near your starting location you can delay researching Irrigation until you expand into new areas. It is a leaf tech, so you won't need it to continue further down the tech tree; if you don't have immediate use for it you shouldn't waste your research time.
The other reasons for researching Irrigation sooner can be if you want an early Wonder (the Hanging Gardens aren't as coveted by the AI as, say, Stonehenge, and their location requirements are easily met), or if you start in a particularly swampy area and you need to clean some space for districts and wonders. Otherwise, go for more important late-Ancient Era techs, such as Writing or Bronze Working.
Note that in order to activate the Eureka moment for this tech you need to build a Farm on a resource (either Wheat or Rice) - a Farm built on plain land won't do.
Civilopedia entry Edit
Irrigation has been a central feature of agriculture for over 5000 years, and forms the basis for the economy and culture of many civilizations throughout history. Perennial irrigation was first practiced in Mesopotamia with water flowing through small channels connecting to a river or a small lake. In Egypt, several pharaohs during the Twelfth Dynasty used oases to store water for irrigation during the dry season. Ancient Nubians devised a waterwheel device to bring water to their fields around the second millennium BC. Terrace irrigation evolved in pre-Columbian America, in Syria, China and India.
The first hydraulic engineers recorded in history were Sunshu Ao (6th Century BC) and Ximen Bao (5th Century BC) of China who both worked on extensive irrigation projects for the emperor (whoever that happened to be at the time) in the Sichuan region; with waters from the “four circuits of rivers” lifted into and moved through channels by chain pumps powered by humans or oxen, it was a marvel of ancient engineering.
Although it is not known precisely how the famed Hanging Gardens were irrigated, they may well have used the noria, invented around this time. The noria is a wheel with buckets or pots along its circumference. As the wheel rotated – driven by flowing water – the upper buckets emptied by gravity into a trough or channel. The wheel, turning, returned the empty buckets to be refilled. Pretty clever, since it didn’t depend on muscle power.
It would be a thousand years before the next advance in irrigation: the windmill, designed to pump water upward into pipes or ditches to water the fields; the technology spread across Europe, allowing for population growth not seen before. That led to more irrigation. It is estimated that there are approximately 600 million acres being irrigated worldwide now.