Groundwater: the invisible resource

Fifty years' worth of subsidence in California's Central Valley due to groundwater overdraft. By 1970, subsidence of more than 1 foot had affected more than half of the valley — and in some areas had reached 28 feet.


EDITOR'S NOTE: Late in the day on August 29, the California legislature passed a package of bills that will, for the first time ever, require monitoring and management of groundwater in this state. TU's California Director, Brian Johnson, and Water Policy Director Chandra Ferrari had a hand in shaping this legislation. The new law will ensure that the needs of fish are part of the water equation in every watershed, and should help sustain adequate streamflows for trout and salmon at critical times. #historicvote #groundwater


By Chandra Ferrari

If you don’t have the pleasure of spending every waking moment with young children, I can tell you one thing about them -- they are insatiably curious. Every day my three kids subject me to a barrage of questions that I either can’t answer satisfactorily or to which my answer prompts even more questions. 

Here are a couple of my favorites. What is air? Why aren’t dinosaurs still alive?  

I recently drove past Lake Shasta, one of the largest and most important reservoirs in California, with my 5-year old. The water level in this reservoir is currently at 30% of capacity (47% of its historical average for the date). My daughter asked why the water was so low. So we discussed drought. 

Twenty questions later it was clear she was concerned that it might not ever rain again. I told her we try to save water when we have lots of it so that we can use it when it is not raining. I told her we can use water that is saved in the ground. 

That opened the gates. How do you know how much water is in the ground? Can you see the water? Where does it come out? 

Coincidentally, the California legislature is today contemplating similar questions as it considers adopting new legislation (AB 1739 and SB 1168) that more comprehensively manages groundwater resources in California.

California holds the dubious distinction of being the lone western state that lacks comprehensive groundwater regulation. 

Over-pumping groundwater can negatively affect fish and ecosystems, water supply reliability, and our ability to develop resiliency to drought. Yet it is surprisingly easy to suck too much groundwater in California right now. Even my 5-year old could aks this question: if we know how important groundwater is, why do we continue to pump it out with no regard for its limitations or effects on other people and the environment? 

Many streams and rivers in California depend on groundwater supplementation during the dry season to maintain sufficient temperatures and flows for trout and salmon. But the current withering drought here has caused even more pumping of groundwater (now 60% of the state’s total supply), leading to many streams being dewatered entirely.

Over-pumping of groundwater in the San Joaquin Valley has caused land to sink at the rate of 1 foot per year in certain areas, damaging infrastructure such as roads and, ironically, the canals that move water around the state via the federal and state water projects. This lost aquifer capacity can never be recovered.

Lost aquifer capacity is also lost water storage capacity, as our aquifers have many times the storage volume of California surface reservoirs. California has already lost more aquifer storage capacity than can be held in Lake Shasta due to over-pumping of groundwater.

Groundwater is California’s primary buffer against drought. This year alone, it is estimated that over 20 million acre-feet will be pumped from aquifers to help meet California’s water demand. This is more water than could be stored in four reservoirs the size of Lake Shasta.

Everyone now recognizes that this rate of extraction is unsustainable.

So we are finally working on this issue – for decades, the “elephant in the room” in California water policy debates. The proposed legislation aims to ensure that groundwater basins are managed sustainably in the future, including avoiding significant effects on surface flows and instream beneficial resources like water quality.

With such huge stakes, both for the ecology and for people, why California hasn’t taken this step earlier? A big part of the reason is the “invisible” nature of groundwater. Impacts to surface flow from groundwater diversions are not always discernible. In fact, groundwater pumping may not have an effect on stream flows until months or even years later and can continue to affect streamflow levels long after the pumping has stopped.

AB 1739 and SB 1168, while not perfect, do propose several steps in the right direction. For instance, high and medium priority basins (as determined by the state Department of Water Resources) will be required to create groundwater sustainability plans, developed by local agencies. The plans may establish pumping limits to ensure groundwater withdrawal does not exceed the rate of aquifer recharge, as well as measures to facilitate sharing of information and public participation in the process.

Importantly, the legislation also provides a state backstop (trigger that could restrict or curtail pumping) in specific instances should local efforts at developing or implementing groundwater plans prove inadequate. In addition, for the first time, impacts to fish and wildlife will be among the criteria used to guide whether a groundwater basin should be designated as high, medium or low priority.

Sustainable management of our groundwater resources is key to preserving California’s fish and wildlife resources, especially during times of drought. It’s vital for strengthening our ability to manage our water supply and the communities and industries that depend on it. And it’s important for enhancing our ability to respond to the effects of climate change. 

A bonus is that it may also help to credibly answer the questions of a 5-year old. 


Chandra Ferrari is California Water Policy Director for Trout Unlimited.


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