What was Percival Lowell convinced Martians were attempting via the observed canal networks?

Piping water from melting polar caps to irrigate their dying world

Percival Lowell became deeply obsessed with the perceived Martian canal network, dedicating his observatory in Flagstaff, Arizona, almost entirely to mapping these supposed features. His conviction was that these lines represented the engineering efforts of intelligent Martians. Specifically, Lowell theorized that these Martians were constructing a vast system to pipe water—drawn from the planet's melting polar caps—across the arid surface to sustain their civilization on a dying world. Lowell's detailed drawings and subsequent publications cemented this romantic, highly advanced image of Martian engineers in the public consciousness during the late 19th and early 20th centuries, often outweighing drier data suggesting a barren planet.