From the Introduction:
Given how dry and arid the surface of this rocky desert is one might not even begin to suspect the tremendous amounts of groundwater hidden below the topmost layers of porous and permeable layers of rock. In this place though the water washed out a small cave over the course of the years until its ceiling collapsed, creating one of the few easily accessible waterholes for many miles. “Easily accessible” has to be taken with a grain of salt though. Depending on the groundwater level one still has to climb down a series of high and steep steps to reach the water. And during the rare rainstorms, when this incline becomes wet and slippery while the water level rapidly rises this lifesaving waterhole might just become a death trap.