If it were only about DRINKING WATER, it wouldn't be that difficult.
Each person needs barely more than 5 liters of it per day. So, a reverse osmosis system is set up on the beach, and the desalinated water is bottled in various sizes.
In Mexico, this type of water supply is standard; even neighborhood water stations are filled this way – only they usually use normal groundwater or surface water for reverse osmosis. Virtually no one drinks the tap water there.
However, it is also the case that even in dry, coastal cities like Lima in Peru, where there is only about 110 mm of rain per year, it is possible to convert the rain into drinking water.
Lima has 12 million inhabitants – if you want to provide them with 10 liters of drinking water per person per day, that's 120 million liters. That's 43.8 billion liters per year. This corresponds to the rainfall that occurs on an area of 400 km² there. That's about one-sixth of the city's built-up area. All that would be needed are appropriate retention basins where the surface water can collect and then be treated. At the same time, this would solve the problem of flooding, which often occurs in desert cities due to runoff from rainwater because there is no stormwater drainage system.
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In Ciudad Juarez, with only 160 mm of rain per year, they've created this rather large duck pond with an adjoining park in a bone-dry environment. Naturally, the pond is still leafless here in March. In the background are the almost completely vegetation-free Juarez Mountains.
The water comes from a retention basin and even from the sewer system. There is a wastewater treatment plant next to the park.
El Paso in Texas, which is located directly across from Ciudad Juarez, even feeds elaborately treated wastewater directly back into the drinking water pipes.
Landing approach to Ciudad Juarez in March 2025.