Scientists have long suspected that the weight of snow and ice in nearby mountains could throw off groundwater assessments tied to elevation changes in California’s Central Valley, but they lacked a way to quantify the effect. A new study demonstrates a solution. (Source: Stanford News)
To help find potential groundwater recharge sites, helicopters deploy spaceship-sized antennas and ping the ground with electromagnetic signals, mapping the geology deep below the surface. The technique was piloted in California by researchers at Stanford, led by Rosemary Knight.
"Much of the modeling that's been done in preparation of groundwater sustainability plans throughout the state assumes that if you stop the water level going down, the subsidence is going to stop. But that's wrong," says Stanford geophysicist Rosemary Knight.
In a new study, Stanford's Rosemary Knight and Matt Lees examined the sinking in one area of the San Joaquin Valley over 65 years and projected that subsidence will likely continue for decades or centuries, even if aquifer levels were to stop declining.
A Stanford University study simulates 65 years of land subsidence, or sinking, caused by groundwater depletion in California’s San Joaquin Valley. The results suggest significant sinking may continue for centuries after water levels stop declining but could slow within a few years if aquifers recover.
Stanford water experts discuss lessons learned from previous droughts, imperatives for infrastructure investment and pathways for the state to achieve dramatically better conservation and reuse of its most precious resource.
The award from the Society of Exploration Geophysicists (SEG) is given to a researcher who has made distinguished contributions both to the advancement of the science and to the profession of exploration geophysics.
Rapidly worsening drought and a mandate to bring aquifer withdrawals and deposits into balance by 2040 have ignited interest in replenishing California groundwater through managed aquifer recharge. Stanford scientists demonstrate a new way to assess sites for this type of project using soil measurements and a geophysical system towed by an all-terrain vehicle.
Naming priorities such as better land management, an evolved portfolio of 21st-century solutions and more funding for research and development, Stanford experts highlight areas central to success as the Biden-Harris administration aims its sights on safeguarding U.S. drinking water.
Stanford researchers, in collaboration with groundwater managers, are leading an airborne survey effort to investigate where water from the Sierra Nevada Mountains could recharge groundwater aquifers in California’s Central Valley.
Stanford Earth's David Lobell, Rob Jackson, Erik Sperling, Dustin Schroeder, Sally Benson, Roz Naylor, Michael Machala, Rosemary Knight and Kate Maher have received funding for interdisciplinary research to solve major environmental problems.
Research by Rosemary Knight shows that unless action is taken, parts of the Central Valley will sink more than 13 feet over the next 20 years. Stopping it will require strategic replenishment of shrinking aquifers.
Pumping an aquifer to the last drop squeezes out more than water. A new study suggests it can also unlock dangerous arsenic from buried clays. Sinking land may provide an early warning and measure of contamination.
Geophysics professor Rosemary Knight comments on a study she co-authored showing that sinking land caused by intensive groundwater pumping in California is releasing trapped arsenic, a known carcinogen.
Ryan Smith, a doctoral candidate in geophysics, explains research he led showing that continued heavy pumping of groundwater in the Central Valley could threaten water supplies with arsenic contamination.
Stanford Earth’s Rosemary Knight recently spearheaded a project to map underground freshwater resources and forecast the intrusion of saltwater into aquifers beneath the California coastal town of Marina.