A new threat to deal with as you create a massive factory is now rising sea levels! Build dykes (walls) to protect your base from rising tides.
Every 5 minutes, the game checks how much pollution exists and will generate about 1 water tile and 1 desert tile for every 4000 units of pollution it finds. It'll add up so be sure to get walls up or build landfill to protect your factory. Desertification speeds up the water process as it prevents pollution from being absorbed!
Check out these before and after pics with massive pollution.