Future groundwater depletion may exceed long-term sustainability goals set by SGMA in the Central Valley, California, USA (2020-2070)

Ryne Adams smiling wearing a black collared shirt standing in front of greenery

Ryne Adams – MS Candidate
Advisor: Dr. Matthew Weingarten

GMCS 129 – August 4, 2022 at 9 am
watch Ryne’s defense

The Sustainable Groundwater Management Act of 2014 (SGMA) is designed to achieve long-term viability of California’s critically overdrafted groundwater basins. Local-scale groundwater sustainability plans began being published in 2020 and 2021, allowing unprecedented insight into how overdrafted basins plan to achieve long-term sustainability. Here, we compile a large database of SGMA sustainability indicator wells, each of which define a water level elevation target for 2040. Future groundwater depletion is evaluated against those SGMA goals, focusing on the critically overdrafted aquifers of California’s Central Valley. We model future pumping scenarios through 2100 with a state-of-the-art groundwater model for the Central Valley aquifer. In modeled scenarios of increased pumping, we observed between 40% and 50% of indicator wells failed to meet their stated goals by 2040. Large-scale, transboundary groundwater depletion between management areas is evident by 2070. Furthermore, large spatial gaps in SGMA indicator well coverage exist in both the unconfined and confined aquifers, including in areas of projected groundwater depletion. Our analysis suggests three factors may help reach SGMA’s long-term sustainability goals: (1) new or expanded recharge projects to combat pumping-related declines, (2) a higher spatial density of SGMA indicator wells across both aquifers, and (3) mitigation of transboundary depletion between neighboring management areas.