Answer :
Recent advancement in technology allows easier access to water supplies, which in turn, keeps populations more stable and/or increases them where we previously could not sustain life of our own kind in dry regions for long periods of time.
The answer is: Recent advancement in technology allows easier access to water supplies
Dry area typically has higher temperature, little amount of vegetation, and very few water reserves. Because of this, Before the advancement in that technology, not many people are willing to live in dry area.
After the advancement in technology, it is become possible to distribute the water from water supplies in other regions to the dry area. This eliminates most of the problems in dry area and more people become willing to live in dry area.