Data

How "Feet Down" is Computed

The USBR publishes two daily readings for a reservoir: the volume of water it holds ("af", acre-feet) and the water surface elevation ("fb", feet). This site works in elevation — "feet down" is how far the surface sits below the fullest the lake has ever been. The method:

• Each day's elevation is read off a single volume → elevation curve fit to the whole record: an isotonic fit — a curve constrained to only rise as the lake fills. A given volume always sits at the same elevation, so this curve is the real relationship; reading off it smooths the small day-to-day noise away for free.
• A handful of gross transcription errors — elevations off by many feet — are dropped before the curve is fit, and the occasional corrupt volume is repaired. The corrected data days are listed below.

Lake Keechelus — Data Corrections

Lake Keechelus's elevation record runs 1915-01-01 to 2026-08-20 — more than 40,000 daily readings.

The record starts in 1915, the earliest measured surface elevation on the gauge's current datum. Nothing here is inferred; the low early years are real measurements.

14 gross-corrupt days — elevation readings off by many feet (transcription errors) — are excluded from the volume→elevation curve:

• 1921-03-25
• 1924-02-16
• 1924-06-16
• 1927-01-09
• 1929-07-24
• 1944-12-04
• 1950-03-14
• 1960-08-16
• 1960-08-17
• 1961-11-27
• 1961-11-28
• 1961-11-29
• 1968-09-16
• 1976-08-25

1 volume repair — a corrupt volume cell replaced by an audited interpolation of its good neighbours (a bad volume can't self-correct the way a bad elevation does):

• 1919-01-30 → 28,586 acre-feet

About the Raw Data

Highest / Lowest Lake Levels Per Year

Volume is in acre-feet.