At Metropolitan Water District’s May Imported Water Subcommittee meeting, Christopher Martin, executive policy advisor for the State Water Project at the California Department of Water Resources, outlined the extent of subsidence along the California Aqueduct, the state’s response strategy, planned corrective measures, and the funding now being assembled for repairs. 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. … 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.

Other groundwater news:

• California Department of Water Resources: News release: Public comment period opens for a groundwater sustainability plan for the Delta-Mendota Subbasin
• California Department of Water Resources: News release: Department of Water Resources releases approved determination for the very low-priority San Gabriel Valley Basin groundwater sustainability plan
• City of Roseville (Calif.): Blog: Capturing water when it’s available, saving it for when it’s needed