Stanford study documents sinking in San Joaquin Valley and looks for potential solutions

STANFORD, Calif. (KGO) -- With views stretching off to the horizon, it's hard to visualize the San Joaquin Valley sinking--unless, of course, you have a measuring stick about the size of a telephone pole.

We found one in the archives of the United States Geological Survey: a photograph showing a man standing next to a tall pole, adorned with signs marking the level of the valley floor, which had already dropped by nearly 30 feet in some places between the 1920s and the 1970s.

"And that photo is, it's something that we use to talk about past events that show how extreme subsidence can get," said former Stanford researcher Matthew Lees, Ph.D.

Lees and senior researcher Rosemary Knight, Ph.D., from Stanford's Doerr School of Sustainability, also have some predictions for the future. In a newly released study, the Stanford team combines satellite data from multiple decades with readings from ground-based GPS stations. The result is a kind of three-dimensional map, pinpointing the areas most affected by the over-pumping of groundwater in the Central Valley and the rate they're still sinking.

"And what we've shown in this study is that, well, it's not just something from the past. It's happening now and what's more, it's faster than it has been, faster than it was before," Lees said.

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Levels have been continuing to drop as much as a foot in many of the years since 2006. But with those measurements, comes the beginning of a possible solution. When we first met Professor Knight several years ago, her team was pinging the valley floor with electromagnetic antennas suspended from a helicopter, mapping California's underground aquafers and the soils that run through them.

The goal: to identify super porous basins and farmland that could be flooded or pumped with diverted water to recharge the sinking aquifers. She says adding in the new precision mapping data could help do that, and more.

"We are trying to integrate these two data sets. The big picture that we see with our geophysical images of the subsurface where the sands and gravels, where the clays and then the satellite-based measurement that's giving us very precise measurements of the way in which the ground elevation is changing," Knight said.

Based on calculations from the California Department of Water Resources, Knight's team believes there's enough surplus water in most years to reverse much of the damage if it's sent to the most critical areas. She points to damaged aqueducts with ground collapsing beneath them and wells too dry to supply safe drinking water.

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"Let's be even more strategic and let's target those areas where the subsidence is causing significant economic or human damage. Let's target those areas where subsidence is causing significant negative impact on human well-being or has a large economic impact," Knight argues.

And perhaps, begin to reverse the damage that's literally pulled California down, for decades.

Just to underline the scale, the team points out that the problem encompasses an area roughly half the size of New Jersey. And a shift that one government report called "one of the single largest alterations of the land surface attributed to humankind."

More information can be found here.