Mexico City has more rainfall than London, yet because the necessary water infrastructure systems have not grown with the development of the rapidly expanding city, it suffers from water shortages that are in parallel with a desert. People living in Tlalpan, an area in the south of Mexico City, have to rely on water delivery trucks, known locally as pipas, for most of their water supply. This is also due to their water mains connectivity being particularly bad. Pipas are unreliable, inefficient and expensive.
Rain water harvesting is virtually nonexistent in the Lake Chapala region despite the fact that there are thousands of gallons of free water especially in the rainy season. All that water simply flows into Lake Chapala but it could be put to much better use for things like irrigation, toilet flushing and laundry. If primary filtration is added to the rainwater harvesting system it can also be used for potable water needs.