Sierra water vs snow mismatch
Sierra reservoirs sit at about 117% of historical early‑March average, yet actual snowpack is below normal — that means surface water looks healthy now but streamflow later could be weaker than expected analysis. In the PCT region, Oregon saw a record atmospheric river that beefed up Cascades snow, but warmer air is turning mid‑elevation precipitation to rain — a volatile mix hikers must watch report.
Statewide reservoir storage was running above the long‑term average — roughly 114% of historical storage in late‑winter — a factor the California Department of Water Resources cited when it raised the State Water Project allocation to 30% on Jan. 29, 2026. water.ca.gov Lake Oroville held about 3.0 million acre‑feet (≈88% of capacity), which DWR reported as roughly 129–132% of its historical average in early March 2026. water.ca.gov San Luis Reservoir registered near 1.79 million acre‑feet of storage (≈88% of its capacity) on March 13, 2026, according to federal reservoir operations records used in regional forecasts. cnrfc.noaa.gov SNOTEL and NRCS basin updates show Sierra snow water equivalent well below median in many basins — Truckee basin index about 51% and several Tahoe/Truckee sites in the 40–50% range — leaving mountain snowpack materially under April‑1 norms. wcc.sc.egov.usda.gov NOAA/CNRFC and California water‑supply briefings note the mismatch: surface storage is bolstered by rainfall and reservoir carryover, but low SWE reduces expected spring and summer runoff, lowering streamflow forecasts for key Sierra watersheds in Bulletin 120 releases. content.govdelivery.com In the PCT/Cascades corridor, a late‑January/early‑February atmospheric‑river sequence set new local records and dumped large precipitation, yet unusually warm air pushed the rain‑snow line upward — the storms boosted high‑elevation snow while converting mid‑elevation precipitation to rain, increasing avalanche, flood and landslide reports across Oregon including incidents around Mount Hood. cw3e.ucsd.edu
