Water that humans use is not always found on the surface of our planet. Digging for water is an ancient practice that in modern times involves drilling deep into the rock to find large fields of water known as aquifers. (My own water supply here on Long Island comes from one of three aquifers — more about them in an upcoming post.) Once a deep well is drilled into an aquifer, we can use pumps to bring that water to the surface, where we can use it for drinking, for irrigation, for manufacturing.
One of the problems of using an aquifer as a water source is the rate of recharge. Water in aquifers typically has accumulated over thousands of years, from rainfall that seeps slowly through the soil and into the underlying porous rock. In many places the water is pumped out much faster than Nature can refill it. When this happens in an inland area, it can result in subsidence — the land above the aquifer sinks as the porous rock, no longer containing as much water, compresses. There are famous cases in California’s Central Valley where pumping has led to many, many feet of subsidence, breaking up roadways, destabilizing the foundations of homes, damaging the pumping system itself.
An article in the latest issue of Geophysical Research Letters by Wetzler et al., Earthquake Swarms Triggered by Groundwater Extraction Near the Dead Sea Fault (see also a recent News item in the journal Science) reports that swarms of earthquakes around the Sea of Galilee in Israel are due to increased levels of groundwater pumping.
Continuous groundwater extraction from several wells located ~10 km west of the swarms has accelerated since 2010 and resulted in a total decrease of ~50 m of the groundwater level at the time of the 2018 earthquake swarm. The withdrawal also corresponds to surface subsidence of ~10 mm/year….Wetzler, N., Shalev, E., Göbel, T., Amelung, F., Kurzon, I., Lyakhovsky, V., & Brodsky, E. E. ( 2019). Earthquake swarms triggered by groundwater extraction near the Dead Sea Fault. Geophysical Research Letters, 46. https://doi.org/10.1029/2019GL083491
It has been known for some time that pumping water into rock to extract natural gas or oil, the process known as fracking, can trigger earthquakes. Now we know that pumping water out can do the same. Both of these processes provide resources that humans depend on — water, which is essential to human life, and fuel, which powers our lives. In the case of fracking, there are alternatives (not necessarily easy or cheap) to oil and gas that can be used to provide power without disturbing the rock beneath our feet. Water, by contrast, is something we cannot live without. How can we preserve our aquifers and prevent the damage caused when we drain them?