About

Editorial policy

This site displays public agency hydrological observations with full historical context and source attribution. It makes no causal or policy claims. Provisional data is labeled as provisional.

Data sources

• CDEC — CA Dept. of Water Resources, California Data Exchange Center: reservoir storage & elevation, Sierra snow, Oroville inflow.
• USBR RISE — U.S. Bureau of Reclamation: Lake Mead & Lake Powell elevation, storage, and Powell unregulated inflow.
• USGS NWIS — daily streamflow (Merced at Happy Isles; Colorado at Lees Ferry).
• NRCS AWDB — USDA SNOTEL snow-water-equivalent; the Upper Colorado basin index is computed from active SNOTEL stations (Σ SWE ÷ Σ median).

All sources are U.S. federal or California state public-domain works.

Conventions

• Percent-of-normal uses the full period of record.
• Charts default to the last 5 water years; the full record is available by zooming out. Water year = Oct 1 – Sep 30.
• Shaded band = p10–p90 climatology; dashed line = median.

Provisional data subject to revision. Public agency observations only — no causal or policy interpretation.