Fundamentally flawed idea.
Places that need water are the most are dry, they have no humidity, as there is little to no water in the air.
The Sahara desert has a relative humidity of 25% (on average). Humidity tends to be much higher in deserts at night. Atacama can go to 0-2% _at noon in direct sunlight_, but as high as 50% at night.
The driest location on the planet is probably Antarctica. Yes, full of water, in the form of ice, but the air is dry.
If you want to support a civilization you better switch to something that can exploit the volume for increased efficiency, like an actual desalinization plant and a solar concentrator powerplant to run it.