Recovery of Daily Water Levels in the Sacramento‐San Joaquin Delta, 1915–2023

ABSTRACT This manuscript documents the data rescue, digitization, and quality assurance of archival daily maximum and minimum water levels at twenty‐five sites within the Sacramento‐San Joaquin Delta. The records encompass 1846 total unique years, where 915 years are newly digitized from the 1915–1985 era. The period of record for each gauge location varies from 40 to 109 years (median = 80 years). Quality assurance procedures and datum corrections were applied to both archival and digital records to generate a time series referenced to a common geocentric datum. Both riverine and coastal influences on mean sea level and great diurnal range are evident in the time series. During the winter months, when river discharge is large, mean sea‐level increase and great diurnal ranges decrease. The strongest river influence is observed at more landward sites, where daily mean sea levels can increase by 1–10 m. The data also include spatially and interannually varying extreme water levels and show evidence of the influence of seasonal tidal barrier construction/dismantling, which began in the late 1980s. The data records thus enable future analysis of multiple intertwined issues, including sea‐level rise, subsidence, tides, climate patterns, atmospheric conditions, shoreline/habitat changes, bathymetric modifications, water resource management, and flood hazards.