Will California Groundwater Ever Fully Recover?

The short answer is probably not even if there are several years in a row of heavy rain and snow fall, and definitely not given the most likely climate projections.

Groundwater is water that is held in a layer of rock and sediment known as the aquafer. There are two types of aquafers, unconfined and confined. The unconfined aquafer is recharged by lakes and rivers percolating down and saturating the sediment above the bedrock. The confined aquafer is recharged by cracks and openings in the bedrock, mostly in mountainous areas.

Groundwater is a basic system. The groundwater itself is in storage. and there are inputs and outputs. The inputs are rain and snow. The outputs can be natural, such as a spring, that feeds a river that ultimately flows to the ocean. Or, outputs can be created by humans, mostly through drilling wells and pumping. If more goes in than is taken out, the amount in storage goes up, until it reaches a limit, and if more is extracted than goes in through recharge, the amount in storage goes down.

But, when groundwater is extracted at rate faster than it can be recharged for an extended period, something else happens. The layers of sediment and gravel can compact, lowering the level of the surface, and resulting in a decreased capacity.

This has been going on for decades in California, and has only gotten worse with the recent years of drought. Ground surface levels have dropped, sometimes as much as 30 feet.

At this point, we can be pretty sure that we are pumping at an unsustainable rate, but how bad is it? Truth is, since the aquafer is kinda hidden underground, it is hard to tell. Ars Technica is reporting on new research which uses a combination of satellite measurements, measurements around specific wells, and modelling of the inputs and outputs to measure and estimate just how much water there is in aquafer. The hope is that with more precise measurement, management and regulation will improve.

Let’s hope so.

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