64 years of daily water-surface elevation, 1963-12-28 to 2026-08-06 · USBR 919 · USBR (Glen Canyon Dam)
On August 6, 2026 this lake is lowest for this date in the whole record. Across 64 years of record, the median reading for this date is 3,634.33 ft, so today is -112.90 ft against its own history — the 2nd percentile.
A percentile pools every reading within seven days either side of this calendar date, across the whole record, and asks where today falls. It is a comparison of this lake to itself, never to another lake, and never a share of capacity.
What this lake usually does on each day of the year, with 2026 drawn over it. The pale band is the 10th to 90th percentile, the darker band the 25th to 75th, and the line through the middle is the median.
The number that matters is rarely the lake's. It is the elevation of your ramp, your dock, your boat lift, or the shallow spot you would rather not find. Type it in and this almanac will tell you what the water has actually done against it.
Everything is computed in your browser from the record embedded in this file. Nothing is sent anywhere, and this works with no internet connection.
Over 63 complete years the lake has typically peaked in July and bottomed out in December. The median gap between the year's high and its low is 28.1 ft; the worst year in the record swung 97.5 ft, the calmest just 13.5 ft.
| Month | 10th | 25th | Median | 75th | 90th | vs full | Readings |
|---|---|---|---|---|---|---|---|
| January | 3,535.65 | 3,582.91 | 3,620.82 | 3,666.97 | 3,681.23 | -79.2 | 1,953 |
| February | 3,532.18 | 3,577.95 | 3,616.50 | 3,664.50 | 3,678.41 | -83.5 | 1,780 |
| March | 3,528.86 | 3,575.53 | 3,613.43 | 3,663.27 | 3,677.43 | -86.6 | 1,953 |
| April | 3,526.98 | 3,575.42 | 3,612.01 | 3,663.33 | 3,677.27 | -88.0 | 1,890 |
| May | 3,533.92 | 3,583.36 | 3,620.79 | 3,665.31 | 3,682.62 | -79.2 | 1,953 |
| June | 3,545.26 | 3,599.80 | 3,633.85 | 3,674.29 | 3,692.55 | -66.2 | 1,890 |
| July | 3,546.64 | 3,606.93 | 3,636.10 | 3,678.90 | 3,696.43 | -63.9 | 1,953 |
| August | 3,549.70 | 3,602.78 | 3,633.40 | 3,675.18 | 3,693.49 | -66.6 | 1,928 |
| September | 3,546.28 | 3,599.18 | 3,629.78 | 3,672.81 | 3,689.83 | -70.2 | 1,860 |
| October | 3,544.60 | 3,599.24 | 3,627.85 | 3,672.44 | 3,687.64 | -72.2 | 1,922 |
| November | 3,543.04 | 3,599.80 | 3,626.75 | 3,671.32 | 3,686.46 | -73.2 | 1,860 |
| December | 3,540.33 | 3,596.47 | 3,624.74 | 3,668.98 | 3,684.95 | -75.3 | 1,926 |
Share of every day in the record that the lake sat at or above a given elevation. Read it downward: pick an elevation on the left, read across for how much of the record cleared it.
The highest and lowest reading in every calendar year of the record, with the dates they happened. The record low is 3,394.50 ft on May 11, 1964; the record high is 3,708.34 ft on July 14, 1983.
| Year | Low | On | High | On | Mean | Swing |
|---|---|---|---|---|---|---|
| 2026 | 3,521.43 | 2026-08-06 | 3,540.17 | 2026-01-01 | 3,529.14 | 18.74 |
| 2025 | 3,540.31 | 2025-12-31 | 3,571.83 | 2025-01-01 | 3,554.97 | 31.52 |
| 2024 | 3,558.21 | 2024-04-16 | 3,587.17 | 2024-07-09 | 3,572.20 | 28.96 |
| 2023 | 3,519.92 | 2023-04-13 | 3,584.68 | 2023-07-08 | 3,554.84 | 64.76 |
| 2022 | 3,522.24 | 2022-04-22 | 3,539.84 | 2022-07-03 | 3,530.15 | 17.60 |
| 2021 | 3,537.33 | 2021-12-31 | 3,582.06 | 2021-01-01 | 3,557.57 | 44.73 |
| 2020 | 3,582.21 | 2020-12-31 | 3,611.02 | 2020-06-22 | 3,600.11 | 28.81 |
| 2019 | 3,568.51 | 2019-04-10 | 3,621.68 | 2019-08-03 | 3,596.95 | 53.17 |
| 2018 | 3,581.85 | 2018-12-31 | 3,622.74 | 2018-01-01 | 3,604.11 | 40.89 |
| 2017 | 3,593.85 | 2017-03-15 | 3,635.80 | 2017-07-11 | 3,616.94 | 41.95 |
| 2016 | 3,591.14 | 2016-04-15 | 3,621.45 | 2016-07-09 | 3,604.74 | 30.31 |
| 2015 | 3,589.82 | 2015-05-07 | 3,614.32 | 2015-07-14 | 3,601.47 | 24.50 |
| 2014 | 3,574.21 | 2014-04-12 | 3,609.68 | 2014-07-11 | 3,593.79 | 35.47 |
| 2013 | 3,584.43 | 2013-12-31 | 3,609.62 | 2013-01-01 | 3,595.83 | 25.19 |
| 2012 | 3,609.82 | 2012-12-31 | 3,639.63 | 2012-01-01 | 3,628.87 | 29.81 |
| 2011 | 3,609.70 | 2011-04-09 | 3,660.90 | 2011-07-30 | 3,635.90 | 51.20 |
| 2010 | 3,618.62 | 2010-04-14 | 3,638.82 | 2010-06-30 | 3,628.63 | 20.20 |
| 2009 | 3,609.70 | 2009-04-17 | 3,642.30 | 2009-07-13 | 3,626.56 | 32.60 |
| 2008 | 3,588.24 | 2008-03-09 | 3,633.72 | 2008-07-16 | 3,612.42 | 45.48 |
| 2007 | 3,594.64 | 2007-12-31 | 3,611.68 | 2007-06-25 | 3,602.38 | 17.04 |
| 2006 | 3,588.66 | 2006-04-07 | 3,610.87 | 2006-06-22 | 3,600.83 | 22.21 |
| 2005 | 3,555.10 | 2005-04-08 | 3,608.38 | 2005-07-12 | 3,585.85 | 53.28 |
| 2004 | 3,564.42 | 2004-12-31 | 3,597.06 | 2004-01-01 | 3,579.87 | 32.64 |
| 2003 | 3,597.22 | 2003-12-31 | 3,619.94 | 2003-01-01 | 3,607.89 | 22.72 |
| 2002 | 3,620.10 | 2002-12-31 | 3,656.08 | 2002-01-01 | 3,637.85 | 35.98 |
| 2001 | 3,656.17 | 2001-12-31 | 3,673.02 | 2001-06-30 | 3,665.32 | 16.85 |
| 2000 | 3,669.89 | 2000-12-31 | 3,683.40 | 2000-06-30 | 3,678.11 | 13.51 |
| 1999 | 3,677.20 | 1999-04-21 | 3,694.73 | 1999-07-16 | 3,685.45 | 17.53 |
| 1998 | 3,672.81 | 1998-03-27 | 3,697.06 | 1998-07-07 | 3,684.95 | 24.25 |
| 1997 | 3,663.08 | 1997-03-22 | 3,695.09 | 1997-07-10 | 3,680.55 | 32.01 |
| 1996 | 3,671.79 | 1996-04-03 | 3,688.31 | 1996-07-07 | 3,679.10 | 16.52 |
| 1995 | 3,644.59 | 1995-03-04 | 3,693.75 | 1995-08-03 | 3,669.13 | 49.16 |
| 1994 | 3,650.02 | 1994-12-30 | 3,665.75 | 1994-06-28 | 3,656.76 | 15.73 |
| 1993 | 3,612.46 | 1993-02-19 | 3,668.70 | 1993-07-18 | 3,644.78 | 56.24 |
| 1992 | 3,615.91 | 1992-12-31 | 3,634.01 | 1992-06-23 | 3,623.88 | 18.10 |
| 1991 | 3,624.55 | 1991-12-31 | 3,639.02 | 1991-06-30 | 3,630.31 | 14.47 |
| 1990 | 3,633.48 | 1990-12-31 | 3,658.42 | 1990-01-01 | 3,646.14 | 24.94 |
| 1989 | 3,658.46 | 1989-12-31 | 3,679.73 | 1989-01-01 | 3,671.58 | 21.27 |
| 1988 | 3,679.76 | 1988-12-31 | 3,693.31 | 1988-07-05 | 3,685.41 | 13.55 |
| 1987 | 3,677.47 | 1987-03-05 | 3,698.47 | 1987-06-25 | 3,687.55 | 21.00 |
| 1986 | 3,680.68 | 1986-03-31 | 3,700.02 | 1986-07-27 | 3,688.47 | 19.34 |
| 1985 | 3,674.82 | 1985-03-12 | 3,700.12 | 1985-07-01 | 3,687.18 | 25.30 |
| 1984 | 3,672.99 | 1984-04-18 | 3,702.46 | 1984-07-07 | 3,688.25 | 29.47 |
| 1983 | 3,682.01 | 1983-02-25 | 3,708.34 | 1983-07-14 | 3,693.24 | 26.33 |
| 1982 | 3,661.89 | 1982-02-13 | 3,687.83 | 1982-10-25 | 3,677.34 | 25.94 |
| 1981 | 3,667.47 | 1981-12-31 | 3,681.38 | 1981-01-02 | 3,676.01 | 13.91 |
| 1980 | 3,672.45 | 1980-01-09 | 3,700.59 | 1980-06-29 | 3,684.38 | 28.14 |
| 1979 | 3,626.93 | 1979-02-16 | 3,684.77 | 1979-07-21 | 3,660.79 | 57.84 |
| 1978 | 3,622.29 | 1978-03-06 | 3,652.75 | 1978-07-24 | 3,635.53 | 30.46 |
| 1977 | 3,630.05 | 1977-12-31 | 3,655.40 | 1977-01-02 | 3,646.33 | 25.35 |
| 1976 | 3,655.31 | 1976-12-31 | 3,672.27 | 1976-07-05 | 3,665.36 | 16.96 |
| 1975 | 3,645.34 | 1975-02-28 | 3,674.93 | 1975-07-25 | 3,659.70 | 29.59 |
| 1974 | 3,646.92 | 1974-01-25 | 3,667.35 | 1974-06-30 | 3,654.08 | 20.43 |
| 1973 | 3,590.60 | 1973-04-29 | 3,648.84 | 1973-12-31 | 3,625.13 | 58.24 |
| 1972 | 3,603.02 | 1972-10-06 | 3,619.71 | 1972-06-27 | 3,610.51 | 16.69 |
| 1971 | 3,598.80 | 1971-01-12 | 3,622.34 | 1971-07-11 | 3,610.15 | 23.54 |
| 1970 | 3,566.62 | 1970-05-01 | 3,601.77 | 1970-07-15 | 3,587.02 | 35.15 |
| 1969 | 3,539.39 | 1969-01-01 | 3,581.18 | 1969-07-21 | 3,563.80 | 41.79 |
| 1968 | 3,513.30 | 1968-05-05 | 3,550.38 | 1968-08-20 | 3,534.77 | 37.08 |
| 1967 | 3,502.23 | 1967-05-22 | 3,532.85 | 1967-07-27 | 3,521.68 | 30.62 |
| 1966 | 3,521.45 | 1966-12-31 | 3,545.68 | 1966-06-09 | 3,534.94 | 24.23 |
| 1965 | 3,490.76 | 1965-03-18 | 3,534.63 | 1965-12-31 | 3,511.64 | 43.87 |
| 1964 | 3,394.50 | 1964-05-11 | 3,491.99 | 1964-12-28 | 3,453.47 | 97.49 |
| 1963 (partial) | 3,409.00 | — | 3,409.60 | — | 3,409.30 | — |
Every figure in this almanac is computed from one series: the daily
reservoir pool elevation published by
USBR for site 919
as parameter 49, in feet above
the Reclamation pool datum (NGVD 1929). The station page is
https://www.usbr.gov/uc/water/hydrodata/reservoir_data/919/csv/49.csv.
0 readings (0.000% of the raw series) were discarded before
any statistic was computed: 0 fell outside a robust band around
the record's own median, and 0 were single-day jumps larger than a
reservoir surface can physically make. Nothing was smoothed, interpolated or back-filled. The
discarded rows are the only difference between daily-record.csv in this download
and what the agency serves.
What this almanac does not do. It reports what the water has done. It does not tell you whether a ramp is open, whether a dock floats, or whether it is safe to launch. Closures depend on elevation, but also on staffing, silt, maintenance and — in California through 2025 and 2026 — invasive-mussel inspections that closed ramps at lakes which were not low. Use the elevation tool above with a threshold you have verified yourself, and confirm current conditions with the operating agency before you tow anything.