About & Methodology

Every number traceable to an official government gauge.

Western Reservoir Conditions·Daily·No. 91·Thursday, October 22, 2026

What this site is

Reservoir Bench republishes the official daily record for 21 major Western US and Texas reservoirs in one fast, citable place: current surface elevation, storage, percent full, record-low and percent-of-average context, and the full daily history downloadable as CSV. It is built for people who want the number and its source, not commentary.

How the “how full” bands are defined

Percent full is storage divided by the reservoir's published capacity - the capacity basis and its source for every reservoir are in the table below. The plain-English band shown next to it is a fixed cut on that percentage, nothing more:

These bands describe how full the container is, not how bad the drought is, and the two are not the same thing. Lake Mohave and Lake Havasu are regulating reservoirs held near the top of a narrow band by design, so they read “effectively full” in any conditions. A Texas reservoir at 100% is at the top of its conservation pool, which is normal operation rather than a surplus.

The comparison that actually indicates stress is a reservoir against its own average for the same calendar date, which this site shows as “% of the <date> average” wherever the record supports it - at least ten prior years with a reading within three days of the date. Where the record is too short, the figure is omitted rather than estimated.

The bands are fixed and published here so that a number on this site can be checked and reproduced. They are not adjusted per reservoir, per season, or over time.

Sources and update cadence

Colorado River system reservoirs (Lake Mead, Lake Powell, Lake Mohave, Lake Havasu, Flaming Gorge, Blue Mesa, Navajo): the Bureau of Reclamation RISE API daily elevation and storage result series, fetched for the full period of record (Lake Mead since February 1935). California reservoirs (Shasta, Oroville, Folsom, Berryessa, New Melones, Trinity, Don Pedro, San Luis): the California DWR CDEC JSON data service, daily elevation (sensor 6) and storage (sensor 15); CDEC's daily record mostly begins in 1985, and each page states its actual window. Texas and Rio Grande reservoirs (Lake Travis, Lake Buchanan, Canyon Lake, Amistad, Falcon, Elephant Butte): the Texas Water Development Board's Water Data for Texas daily per-reservoir series, full period of record. The site rebuilds daily; each page shows the as-of date of its newest reading. Agencies occasionally revise recent values, and those revisions flow through at the next rebuild.

Percent-full methodology

Percent full = latest storage ÷ a published capacity. For Reclamation and CDEC reservoirs the capacity is fixed and taken from the government operations reports listed below - the same bases the agencies use in their own daily reporting (for Lake Mead, 26,120,000 acre-feet at elevation 1,219.6 ft, the bottom of the exclusive flood-control space). For TWDB reservoirs, percent full is conservation storage ÷ conservation capacity exactly as TWDB publishes it, using the latest conservation capacity in the data (TWDB re-rates capacities as new surveys are adopted). Agencies also publish other capacity figures, so percentages you see elsewhere may differ by a few points.

Record lows and percentile context

Each reservoir page states its record low, record high, and percent-of-average storage for the current calendar date, always computed from the same daily series shown on the page and always with the comparison window stated. Where a record begins during a reservoir's initial fill (Lake Mead 1935, Lake Powell 1963), the record low is reported "since first filling" so fill-era readings are not passed off as drought lows; where a record opens on an already-operating reservoir (CDEC, 1985), the low is reported for that window only.

What this site does not do

No forecasts of our own, no water-supply or investment advice, and no invented statistics. If a value is missing from the source record it renders as "-", never as zero. Explanatory pages (shortage tiers, post-2026 process, dead pool) cite the governing government documents directly.

Projections policy

Reservoir Bench does not model or predict anything. The projections page transcribes figures published by the Bureau of Reclamation in its monthly 24-Month Study, identified by study month and linked to the source PDF. Reporting a published federal projection is an observation about a document, not a forecast by this site. Projection numbers are refreshed manually after each monthly study; the daily gauge readings on every reservoir page update automatically regardless.

Citing this site

All underlying data is US-government public domain. You are welcome to cite or quote any page with attribution and a link to reservoirbench.com. Contact: contact@reservoirbench.com.