In a country as dry as Saudi Arabia, cool watering holes are a big attraction–drawing in locals, their graffiti, and their cameras. The latter two might be an annoyance for folks just looking to cool off, but for scientists in Europe, they can also be valuable data.
By looking through the videos for particular graffiti spray painted on the walls in the cave (known as Dahl Hith or Ain Heet), Michelsen could monitor the water levels, looking for how much the water rose over certain graffiti marks over time. He figured out that the groundwater in the cave was rising at a rate of about 15 inches every month for the past two years. The most likely source for the extra water is probably treated wastewater from a nearby water treatment plant.
Michelsen’s research was presented at the European Geosciences Union (EGU) General Assembly.
Update: An earlier version of this story discussed concerns about the cave’s stability. The rocks that make up the cave are limestone and anhydrite, both of which are easily weathered and eroded by water. Many limestone caves were formed by water slowly hollowing out the ground. Fluctuating water levels in caves can lead to changes in the cave walls, creating a potential safety hazard. Michelsen wrote to us and said that more sound assessments (presumably not just based on YouTube footage) of the situation were still to come.