What Really Lies Beneath: An Introduction to Groundwater

Some portions of the US – Florida, New Mexico, Nevada and Hawaii – already depend on groundwater for more than 80% of their water supply. And groundwater depletion is already a significant problem in California and Arizona, as well as the High Plains states of Texas, Oklahoma, and Kansas. Overuse of subsurface water supplies have resulted in groundwater mining - that is, groundwater, which when managed properly is a renewable resource, is being extracted at rates exceeding the rate of recharge. That means the water levels in important aquifers like the Ogallala are dropping tens and even hundreds of feet.

In coastal regions, aquifer depletion includes the added danger of salt water intrusion. Fresh groundwater is less dense than saltwater, and typically lies above it. But as wells withdraw increasingly greater amounts of fresh water, the groundwater lens becomes smaller and shallower, and salt water is drawn into the aquifer. In other parts of the continent, groundwater mining has caused the land to subside – as much as 21 feet in places like Mexico City and the San Joaquin Valley of California. Galveston, Texas has also suffered land subsidence from groundwater extraction.

While it’s unfortunate that groundwater mining occurs, all the news is not bad. Next week we’ll take a look at ways we can protect and preserve our groundwater supplies. After all – eight tablespoons isn’t much, but it’s all we’ve got!

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