We're becoming used to seeing images of shrinking rivers and reservoirs in much of England and Wales, but what happens to all the rain that doesn't end up in them? A lot of it soaks into the soil, some evaporates and some is absorbed by vegetation. For the rest, you have to take a subterranean turn.
Rainfall that filters down below the soil level is called groundwater, and the rocks which hold groundwater are called aquifers. Andrew McKenzie, a hydro-geologist at the British Geological Survey, said on average about 10% of rainfall ends up as groundwater. This hidden water source moves slowly downhill, taking weeks, months or even years before reaching rivers, wetlands, the sea, or forming springs which rise to the surface.
"There is some good news about that, " said Mr McKenzie. "If you get very heavy rainfall, that rain (which becomes groundwater) is not directly contributing to any flooding, and during very hot and dry periods you still get water that keeps rivers and streams flowing." You can get more environment news and other story updates straight to your inbox by subscribing to our newsletters here.
