By Bill Ehorn, California Department of Water Resources, Northern Region & Allan Fulton, UC Irrigation and Water Resources Advisor
Trends in cumulative spring groundwater change by county are shown in Figures 1 and 2 below for a shallow well monitoring network and an intermediate well monitoring network across five northern Sacramento Valley counties. The period of interest includes the spring of 2011 which was a wet water year, 2012 through 2016 which were a series of dry or critically dry water years, followed by 2017 which has been a record-setting wet year.
The trends indicate that groundwater levels have recovered to 2011 (pre-drought) conditions at both shallow and intermediate zones in the Redding Basin which includes Shasta and part of Tehama Counties. Groundwater levels are still recovering to pre-drought levels in both the shallow and intermediate zones in all counties within the Sacramento Valley Basin. While it is encouraging that groundwater levels are recovering, it appears that more than a single year of above average precipitation is needed for groundwater levels to recover to pre-drought conditions in many areas of the northern Sacramento Valley.