It’s a industry/planning term. It covers spaces which has a water (often drainage criteria). Water is too of a broad term as it can also suggest potable water which is about pipe networks. This where it gets fun, lots of new stuff described as blue-green infrastructure which is a growing hybrid field. Like instead of a concrete storm channel, the same system can made via a constructed methods as a naturalised “green” channel so it is essentially a man-made creek. So we would now call this blue-green infrastructure. Then the information in this article would be used as supporting information on why we should build human interaction points on a piece of blue-green infrastructure to make it now a community amenity when previously it would have just have been an infrastructure solution.