Ralph Hitchcock: Future of Central Valley underground water supply
The recent article in The Union on damage in the Central Valley from subsidence as a result of pumping underground water was very good, but it dealt only with effects on the surface.
There are some other very important long-term consequences which are probably irreversible, such as a permanent and possible drastic reduction of the volume of water which the Central Valley aquifer can hold. To put this into perspective, Lake Mead, the largest fresh water reservoir in the nation contains 26 million acre-feet at capacity.
Since 1962, 80 million acre-feet has been pumped out of the Central Valley aquifer. That is triple the volume of Lake Mead.
Subsidence is a symptom of the compression of underground soil and rocks which results in a permanent loss of aquifer volume. The percentage of groundwater to total water use has risen drastically including an unknown number of recent wells. This is not only because of drought. Much of this is used to irrigate recently planted orchards and vineyards. Some of these new wells had to be over 2,000 feet deep resulting in using water which has been down there for 20,000 years. It is difficult to determine, but there are estimates that as much as 6 million acre-feet of underground storage may have already been lost.
California finally became the last western state to adopt groundwater regulations by recently adopting the Justifiable Management Act. Since its passage, corporate agriculture has been racing to drill new wells while there is still absolutely no regulation. Unfortunately it will not be the state but many local authorities, which are more subject to pressure from corporate agriculture, who must develop the plans and institute regulations on unknown thousands of wells. This act may not be realistically regulating wells until 2040. So pumping will most probably continue to increase, being only partially regulated at best, for 24 more years. So whenever withdrawal is more than refill, the result will be a continuing drawdown leading to permanent loss of underground storage.
The main reason groundwater pumping will continue to increase into the foreseeable future, with or without drought, is because of the great profits to be made in these high value orchard and vineyard crops. These crops cannot be fallowed in dry years but must have water throughout every dry season. A hard fact of water supply life in the Central Valley is that surface water deliveries are fully allocated, amounts are not reliable year after year and can be drastically reduced during shortages. Therefore all of this recent and future expansion of high profit orchard/vineyard agriculture must rely on ground water. This trend is led by corporate agriculture in which short term profits are more important than long term groundwater storage. This is in contrast to family farmers who are concerned about future generations as well as profits.
Considering that realistic groundwater regulation may not be truly functional until 2040, a case could be made that what is being done or will be done is “too little and too late” to significantly protect the precious groundwater basin from permanent and severe reduction in volume.
Ralph Hitchcock is a retired civil engineer. He lives in Nevada City.
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