Where the data comes from

Water surface elevation is the height of the water above a fixed reference, not lake depth, storage volume, or percent full. The unit and vertical datum are shown when provided by the source. An unreported datum is left unknown rather than guessed.

We show the latest available elevation reading for each lake. On a lake page, history and trends use that reading’s station only. Changes are calculated only between readings with matching units and datums, near the stated comparison date; missing comparisons stay unavailable. Historical ranges describe the records available here, not all-time records.

USGS’s connected Lake Powell gauge provides frequent observations, typically at 15-minute intervals. The connected Reclamation RISE elevation series report daily. Neither cadence means this site updates instantly.

Nevada USGS history combines published daily records with the last collected instantaneous reading of each day. Daily dates do not supply an exact observation time; they are stored at midnight Arizona time for ordering, not as an asserted measurement time. Where no daily series exists, history is sampled from the continuous feed. Daily statistics and instantaneous readings can differ, so comparisons describe available reported levels, not exact same-hour changes.

Reservoir parameter 00062 may use a local reference; no national datum is inferred from the station’s ground elevation. Topaz and Marlette values are therefore not sea-level elevations. Lake Tahoe is shared by Nevada and California; its Tahoe City gauge reports height, converted using USGS’s documented formula of 6,220 feet plus gauge height in the Bureau of Reclamation datum.

The site is scheduled to check the feeds every 3 hours. “Observed” is the agency’s measurement time; “Retrieved” is when we saved that record. A site refresh can retrieve the same observation again and does not make it newer. Times are displayed in Arizona time (MST, UTC−7, year-round). Readings older than 48 hours are labeled “Last reported.”

Source values may be provisional and revised. Our collection revisits recent records to capture revisions. A connected source can still have delayed observations; check both the observation time and refresh status before relying on a number.

Lakes without a verified station show no level. Lake map coordinates are approximate, and distances are straight-line estimates—not directions or verified access locations. Boat ramp, marina, fishing, and camping conditions are not inferred from elevation.