These roofs are perfect for arid land restoration/ homesteads in dry areas. Most people collect roofwater off of their house and other structures, which is often adequate. But in desert areas you may need a much larger roof to collect sufficient water, especially if you are gardening. This video does a good job of showing all the parts of a roofwater collection system.
water collection
Warka-Water, Ethiopia
The 30ft high bamboo ‘flower basket’ that can pluck drinking water from thin air
• Structures use condensation to take water from the air in morning fog
• Can be built by villagers and transported to most needed areas by donkey
• Designed to be used in Ethiopia where wells cannot be dug