April 30, 2026
Region 4: San Joaquin & Tulare
Reservoirs
Millerton Lake serves as the focal reservoir for Region 4. A snapshot of current storage conditions from the Department of Water Resources is included below. Adjacent to that, storage levels for the current water year (dark blue) are shown alongside analog years (2018–19 and 2024–25) for context.
Precipitation
As with the Core Supply, regional precipitation is presented using both the corrected NWS data feed and GG Weather values, offering a comprehensive perspective on how precipitation has been distributed across the region. The NWS stations reflect higher-elevation, basin-oriented conditions most relevant to water supply, while GG Weather values represent valley- and coastal-based observations and in situ recharge.
Differences between the two reflect where precipitation has been most concentrated this season. In a year characterized by predominantly warm storms and coastal-focused storm tracks, lower-elevation locations have generally received a greater share of precipitation.
ALICE model output indicates that Region 4 will receive 92.5-112.5% of normal precipitation. Region 4 observed totals range from 88.6% (NWS) to 95.7% (GG Weather) of average. The difference reflects the mixed influence of valley and foothill precipitation, with lower-elevation locations benefiting more from this season’s predominantly warm storm pattern.
NWS data indicates that Region 4 saw 4 inches of accumulation during the month of April, adding 14.6 percentage points to the accumulation.
