‘The Central Valley has many areas where recent groundwater levels are more than 100 feet below previous historical low …’
Farmers in California’s Central Valley pumped more groundwater than ever during the state’s ongoing drought, causing aquifers to drop to new record low levels, according to the U.S. Geological Survey.
The agency recently launched a website to help track Central Valley groundwater depletion and land subsidence. A new paper released about the same time shows geographical nuances in the decline. The biggest changes are in the southern Central Valley, where farmers have shifted from planting annual and seasonal crops to perennial plants.Land subsidence has caused costly infrastructure damage such as canal buckling and reduced freeboard on canals and bridges. At some points, up to 11 inches of land subsidence was measured from 2012 to present.
“The Central Valley has many areas where recent groundwater levels are more than 100 feet below previous historical lows,” said Michelle Sneed, USGS hydrologist. “These correspond to areas of recent active subsidence.”
The article describes recent changes in water availability and, the competition for water in the Central Valley and evaluates how climate variability and human action influence subsidence, particularly during drought.
Since the early 1990s, the availability of surface water has decreased because of operational changes of the federal Central Valley Project and the California State Water Project. Although irrigation has become more efficient, land use in the Central Valley has trended toward the planting of permanent crops, replacing non-permanent annual crops and rangeland.
“As land use, managed aquifer recharge and surface-water availability continue to vary, long-term groundwater-level and land-subsidence monitoring and modeling are critical to understanding the dynamics of the integrated system,” said Claudia Faunt, USGS hydrologist.