Footing: “The part of a foundation bearing directly upon the earth.” That’s the sixth entry for the word “footing” as presented in the Random House Webster’s College Dictionary, 1991 edition (p. 519). But, it’s more than that. That definition also applies to the discussion on tap for today: that having to do with groundwater depletion, its resultant consequence – land subsidence, and what affect this can have on surface building.
Okay, so there is nothing really mysterious about this particular interplay that’s been playing out in many parts of the world.
So, time now to expand more on, in a manner of speaking, the cast of interdependent contributors.
First up, groundwater depletion: It’s not all that complicated an idea. There are what are known as subsurface aquifers. These, located within the ground strata (or more simply, in the ground), contain water. These deposits can be located at different depths depending on just where they happen to reside.
At any rate, when content is removed empty space takes its place, creating a kind of cavity.
Being the land lying above has tremendous weight, when groundwater situated below is removed, that land sitting on top sinks. The term used to describe this action: subsidence. It can be a big deal depending upon where said subsidence occurs and what on the surface is affected by this action.
Turning attention now to contributing factors, global warming and climate change are but one. Regardless, the fallout connected with sinking land can be most impactful.
Take overland water-conveyance infrastructure as just one example. If affected by land subsidence, such conveyance infrastructure could be rendered unusable.
It’s a similar situation for bridges used to permit transit modes using such to get from one side to the other. And, for buildings, the footings on which they sit, can be impacted enough such that building sections or entire edifices can collapse. It is certainly not out of the realm of possibility.
As global temperatures rise, we just may hear or read about more of these types of catastrophic events occurring due to land-subsidence issues.
To try to tackle this action head-on and ensure an adequate aquifer supply and reduce or prevent the possibility of consequential ground subsidence, there is what is known as groundwater recharge. One way to facilitate this is through the process known as percolation, whereby water collecting in surface depressions ultimately seeps into the ground. (For a deeper understanding, see below image).
In addition, water conservation or control measures can be put in place to limit the amount of water consumed, whether having to do with growing crops, watering lawns or whatever other purposes for which water is used.
Above and corresponding, connected home-page-entry images: T.C. Winter, J.W. Harvey, O.L. Franke, W.M. Alley, U.S. Geological Survey via Wikimedia Commons
Last updated on Jun. 28, 2023 at 7:48 a.m. Pacific Daylight Time.
– Alan Kandel