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Water Storage Uncertain

Amount of Groundwater Stored in Aquifers is Uncertain

You may be surprised to learn that science cannot accurately estimate how long our groundwater will sustain the quad-cities. You’d think this would be easy, like managing your money. For example, if you have $1,000 in a savings account, and you withdraw at a rate of $100 per month, how long will your savings last?  That’s easy: 10 months.

With groundwater, it is not so easy. We know the withdrawal rate, but we cannot calculate the amount of water in the Prescott Active Management Area that is actually accessible for municipal and rural pumping. Unlike your bank account, it is impossible to recover all of the groundwater in the aquifer.

The amount of recoverable water stored in the aquifers in the Prescott Active Management Area to a depth of 1,000 feet is estimated by the Arizona Department of Water Resources (ADWR) to range from approximately 3 to 5.2 million acre-feet. Local officials use this estimate to claim that the aquifer contains enough water to last hundreds of years at the present rate of usage. Such a claim is overly simplistic and is not scientifically valid. 

We don’t understand the geology of our aquifers with enough detail to accurately estimate the actual amount of retrievable water. Even if we knew the amount of groundwater in storage, it’s not possible to determine the fraction we might economically recover, but it will be substantially less than the amount stored. 

Simply stated, it is not scientifically possible to accurately estimate the amount of water available from an aquifer or groundwater system based solely on the amount of water in storage.

If you were unsure of your savings account balance, wouldn’t you be extra careful with your withdrawals? Yes. 

Similarly, shouldn’t local officials act conservatively when approving growth that increases water use? Shouldn't they enact water management policies that will reduce - not increase - the demand for water?

Here is a two page document with a more detailed explanation.

DAILY DROPLET

  • "Ranchers need clean water for their stock, farmers need it for their crops, every employer needs it to stay in business, and every living thing needs it for life... The law needs to be clear to protect water quality and the rights of landowners."
    Mark Udall

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    Leonardo da Vinci

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    Benjamin Franklin, Poor Richard’s Almanac, 1746

  • "...and since flow of information is to spirit what water is to life, we'd best think about how to keep the pipes free and unclogged."
    Raphie Frank

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    Rachel Carson

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    Jacques Yves Cousteau

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    Albert Szent-Gyorgyi, 1937 Nobel Prize for Medicine

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