Agency staff measures water levels at more than 90 wells on a monthly basis throughout the Salinas Valley to monitor fluctuations in response to seasonal pumping and recharge patterns. Data from approximately 50 of these wells are used to prepare a quarterly report on conditions in the Salinas Valley Groundwater Basin. Monthly measurements are grouped by hydrologic subarea, averaged, and graphed to compare current water levels and trends with those of selected past years. Graphs for each individual subarea, such as the examples below, show water levels for the current year, the previous year and an exceptionally dry reference year. For comparison to long term conditions, a curve showing monthly water levels averaged over the most recent 30 years is also included on each graph.

As the monthly graphs illustrate, groundwater levels typically reach their highest elevations in late winter or early spring. These peaks are the result of seasonal rainfall, changes in pumping, and the variation in local recharge regimes. Groundwater levels tend to begin a seasonal decline with the onset of spring irrigation and reduced natural recharge. The lowest groundwater levels of the year are usually measured between late summer and early autumn.