NASA Jet Propulsion Laboratory GRACE/FO Central Valley groundwater work

Jay Famiglietti

Global Futures Professor at Arizona State University | Former NASA JPL Senior Water Scientist | Multi-Sectoral Advisor on Global Water Security | Head of Water Innovations for a Sustainable Earth (WISE) Research Group

Excited to see that California Department of Water Resources has really embraced our NASA Jet Propulsion Laboratory GRACE/FO Central Valley groundwater work, and has featured an update as the lead figure in its May 2026 semi-annual update to California's groundwater conditions.
 
This plot did not just happen. It is the result of over 25 years of hard work from our team, starting with Matt Rodell‘s groundbreaking dissertation paper (Rodell and Famiglietti, 2002), our years of work on GRACE/FO Central Valley groundwater (Famiglietti et al, 2011; UCCHM, 2014;  Liu et al, 2022; Reager et al., 2026, in review), and more recently, with JT Reager’s strong liaising.
 
While DWR has been working with JT to update our work for its semi-annual reports for some time, including updates to our cumulative groundwater loss figure first published in UCCHM, 2014, this is the first time I have seen it publish an update to our monthly anomalies. 
 
To my younger colleagues, please don't be impatient. Impact takes time. My first conversations with DWR began a dozen years ago, and included now-retired personnel at both DWR and JPL. DWR was not even publishing the groundwater updates back then. I left JPL in 2018, and the conversation might have otherwise died, but we are lucky that the next generation -- JT Reager at JPL and counterparts at DWR -- were there to continue the dialogue.

Moreover, impact can be extremely difficult to track. I literally stumbled across this figure. It is not the first time that I learned of our impact almost by chance. That has happened at least 3 times in my career -- that I know of.

In the coming months, please keep an eye out for JT Reager’s GRACE/FO Central Valley groundwater recharge paper (I could see the key figure also being published in future DWR updates), revised and in re-review; and for Brian Richter's western US paper, just going into review.