Mexico City Is Always Either Too Wet or Too Dry

There may be other major global metropolises (Los Angeles springs to mind) that have invested more effort and money than Mexico City to bring in water from afar. But there is surely none that has invested as much effort and money to send the water back out.

Mexico City's hydrological paradox is that (unlike Los Angeles) it gets more than enough rain to, in theory, keep the 21 million people who live in and around it adequately supplied with water. Its average annual precipitation is about twice that of Los Angeles, and even exceeds that of famously damp London. But most of the rainfall (or hail, which hit parts of the city early Monday) comes during the summer, and often during just a few epic storms. So when it's wet, it's way too wet, and the city has built a massive infrastructure over the past five centuries to get the water out quickly. To keep hydrated during the drier months, Mexico City imports water from other regions but mainly just pumps from underground, which causes land subsidence, which makes flooding worse.