The Global Network of Canals on Mars

When scaperelli published his sightings of these canali, a lot of astronomers turned their telescopes towards mars to see if they too could see the lines on its surface. They figured that the global network of canals had been built in order to transport water from the polar regions to other parts of the planet. Why would the martians want to do that? Presumably because water wasn't available in sufficient quantities elsewhere on the planet. This created the impression of mars as a ying planet that was running out of water. So the inhabitants needed to conduct this global construction project that dwarfed anything we had built here on earth.