![Department of Water Resources engineering geologists Aaron Cuthbertson (right) and Kimberly Bowman measure groundwater levels at a designated monitoring well, one of thousands of wells in California used to generate groundwater level change reports.](/-/media/DWR-Images/Groundwater/KG_well_monitoring_54891_03_10_20.jpg?mw=200&hash=4E297C973CC74A50FBFE0F6644C8CBC9)
Groundwater is an important resource for Californians because rain and snowfall levels can vary dramatically from year to year. Groundwater provides 40 percent of the state’s water supply in normal years and up to 60 percent in dry years when surface water in lakes, rivers and reservoirs may be reduced.