i love how much i learn in this thread. i can see that, but have no clue about that type of thing. so when you say ditch water, is it literal trenches running this water around? or is it just the quality of water, like runoff. what about wells?
It's a network of small ditches & flow control gates branching from a larger canal that diverts water from a river or reservoir. Here in CO there are even massive collection systems where water is gathered on the western slope at high altitude & diverted under the continental divide to eastern slope reservoirs for agriculture & domestic water. It's highly managed with an arcane set of rules & regulations covered under the general heading of water rights.
This is a map of just one system-
https://www.secwcd.org/content/fryingpan-arkansas-project-system-map