06/02/2026
NOTEBOOK FEATURE: Sinking land, shrinking capacity: DWR confronts subsidence on the California Aqueduct
Maven June 1, 2026
Groundwater-driven land sinking in the San Joaquin Valley is reducing aqueduct capacity, prompting interim repairs and long-term planning.
Subsidence occurs when groundwater pumping lowers water levels and reduces pore pressure in the aquifer system, causing the fine-grained clay and silt layers in the sediments to compact. In the San Joaquin Valley, those compressible clay-rich layers are especially important: they act like weak, water-bearing cushions between coarser sand and gravel aquifers. When pumping draws down groundwater, the clays slowly drain and compress, and much of that compaction can be permanent. As those buried layers thin, the land surface above sinks. Because the sinking is often uneven from place to place, it creates differential subsidence that can distort the slope and freeboard of infrastructure such as the California Aqueduct, reducing conveyance capacity and increasing repair needs.
Subsidence in the Central Valley has been documented since at least the 1920s, driven largely by long-term groundwater pumping in one of the world’s most intensively farmed regions. By the time construction of the State Water Project was completed around 1970, parts of the San Joaquin Valley had sunk by more than 8.5 meters, or nearly 30 feet.
https://mavensnotebook.com/2026/06/01/notebook-feature-sinking-land-shrinking-capacity-dwr-confronts-subsidence-on-the-california-aqueduct/
Jim Property ID
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