Detecting hidden sources
How much water is underground? If you were to extract it all and pour it across the planet’s surface, it would cover Earth’s entirety to a depth of 120 metres. When picturing this volume underground, you might mistakenly imagine it as a flowing body of water. In reality, bodies of groundwater, called aquifers, are soaked up by the solid ground. Just like when you dig in the sand at the beach and water appears to come from nowhere to occupy the space, water hides in small spaces in rocks and soil in a similar way.