An important part of managing groundwater is to prevent or minimize land subsidence. If groundwater levels are lowered too much, the land surface may start to subside.
Land subsidence can lower levees, increasing the threat of flooding.
Subsidence can also damage roads, pipeline canals, buildings, and water wells. Subsidence is monitored by repeated land surveys and by use of scientific instruments called extensometers. DWR's Central District operates three extensometers in the lower Sacramento Valley - two in Yolo County and one in Sutter County. Depth to groundwater levels are measured with a specialized measuring tape at the observation well near an extensometer.