The irrigation works of ancient Sri Lanka, the earliest dating from about 300 BCE, in the reign of King Pandukabhaya and under continuous development for the next thousand years, were one of the most complex irrigation systems of the ancient world.
The earliest agricultural irrigation canal system known in the U.S. dates to between 1200 B.C. and 800 B.C. and was discovered in Marana, Arizona (adjacent to Tucson) in 2009 [REF].