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.

feetdown = -1 * (max(fb_fit) - fb_fit)

Lake Kachess — Data Corrections

Lake Kachess's elevation record runs 1950-01-01 to 2026-08-20 — more than 27,000 daily readings.

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

1951-04-01
1962-07-25
1975-11-27

About the Raw Data

Field	Description	Data Start	Data End	Number Records

Highest / Lowest Lake Levels Per Year

	Maximum Lake Level			Minimum Lake Level
Year	Date	Feetdown	Volume	Date	Feetdown	Volume

Volume is in acre-feet.