HydrionisGlobal Water Intelligence
Monitored reservoir

American Falls Reservoir

American Falls Reservoir is a federal reservoir operated by the United States Bureau of Reclamation in its Pacific Northwest region, with published operating records from 1925.

Storage recordAmerican Falls Reservoir and Dam (AMF)

Storage now, against this reservoir's own record

252.98 Mm³
Stored, August 2026
10th
Percentile among 101 Augs on record
-68.7%
Against the Aug 1991–2020 average
-22.6%
Change over the 12 months to 2026-08

Storage in August 2026 was lower than most Augs on record, ranked against 101 other Augs held for this reservoir.

Storage, 1925–2026

Monthly mean storage
1,211 monthly values, 1925 to 2026
Monthly mean storageMonthly mean storage: American Falls Reservoir in Mm³, from 1925.75 to 2026.5833333333333.01,0002,000Mm³1925.751938.41666666666671951.08333333333331963.751976.41666666666671989.08333333333332001.752014.4166666666667Year

Monthly means of the publisher's daily record. Volume, not percentage of capacity — see below for why.

What the shaded periods are (0 events)

Not shown on this chart

  • The 1976 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • The 2022 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • Yorkshire drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • Cantareira water crisis, São Paulo — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • Cape Town Day Zero — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • European drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
View the data behind this chart
240 of 1,211 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,211 would be longer than this page and unusable with a screen reader.
PeriodAmerican Falls Reservoir (Mm³)
October 19256.27
March 19266.54
August 19267.85
January 1927554
June 19271,906
November 19272,057
April 19281,605
September 19281,295
March 19291,831
August 19291,318
January 19301,022
June 19301,424
November 19301,119
April 19311,873
September 193142.5
February 1932487
July 19321,390
December 1932759
May 19331,639
October 1933340
March 19341,363
August 1934184
January 1935402
June 19351,156
December 1935475
May 19362,075
October 1936785
March 19372,003
August 1937990
January 19381,328
June 19382,108
November 19381,333
April 19392,091
September 1939372
February 19401,499
July 19401,051
December 19401,016
May 19411,990
October 1941538
March 19421,780
September 1942606
February 19431,471
July 19432,078
December 19431,496
May 19442,069
October 1944712
March 19451,898
August 19451,541
January 19461,474
June 19462,107
November 19461,288
April 19472,065
September 1947863
February 19481,699
July 19481,907
December 19481,462
June 19492,086
November 19491,089
April 19501,883
September 19501,178
February 19511,786
July 19511,966
December 19511,755
May 19522,053
October 1952759
March 19532,051
August 19531,235
January 19541,608
June 19542,008
November 19541,100
April 19552,111
September 1955448
March 19561,766
August 19561,336
January 19571,566
June 19572,043
November 1957830
April 19582,092
September 1958352
February 19591,575
July 1959901
December 1959928
May 19601,844
October 196048.7
March 19611,692
August 1961171
January 19621,350
June 19622,068
December 1962936
May 19632,138
October 1963374
March 19641,776
August 19641,305
January 19651,447
June 19652,042
November 19651,424
April 19661,879
September 196694.5
February 19671,550
July 19671,970
December 19671,194
May 19681,963
October 1968931
March 19691,586
September 1969390
February 19701,659
July 19701,956
December 19701,478
May 19712,096
October 19711,629
March 19721,716
August 19721,336
January 19731,335
June 19731,224
November 1973598
April 19741,361
September 1974415
February 19751,283
July 19751,327
December 19751,008
June 19761,387
November 1976531
April 19771,332
September 19771.74
February 19781,357
July 19781,854
December 19781,268
May 19791,938
October 1979115
March 19801,848
August 19801,257
January 19811,517
June 19812,037
November 1981489
April 19821,953
September 19821,452
March 19831,815
August 19831,788
January 19841,365
June 19842,087
November 19841,494
April 19851,822
September 1985487
February 19861,462
July 19862,009
December 19861,226
May 19871,813
October 1987190
March 19881,822
August 1988301
January 1989970
June 19891,732
December 1989765
May 19901,586
October 1990126
March 19911,689
August 1991645
January 19921,166
June 1992941
November 1992436
April 19931,901
September 1993864
February 19941,826
July 1994689
December 1994794
May 19952,062
October 1995855
March 19961,868
September 1996967
February 19971,675
July 19971,961
December 19971,350
May 19982,020
October 19981,144
March 19991,689
August 19991,310
January 20001,441
June 20001,789
November 2000548
April 20012,059
September 200169.3
February 20021,271
July 2002676
December 2002711
June 20031,029
November 2003349
April 20041,538
September 200484.5
February 20051,329
July 20051,252
December 2005889
May 20061,988
October 2006441
March 20071,895
August 2007244
January 20081,000
June 20081,639
November 2008764
April 20092,023
September 2009820
March 20101,977
August 20101,084
January 20111,371
June 20111,986
November 2011964
April 20121,966
September 2012222
February 20131,517
July 2013699
December 2013734
May 20141,901
October 2014438
March 20151,768
August 2015555
January 2016998
June 20161,400
December 2016932
May 20172,015
October 20171,136
March 20181,864
August 2018894
January 20191,515
June 20191,985
November 2019743
April 20202,047
September 2020596
February 20211,616
July 2021421
December 2021795
May 20221,629
October 2022134
March 20231,458
September 2023421
February 20241,618
July 20241,458
December 2024956
May 20251,962
October 2025175
March 20261,582
August 2026253

The reservoir's year

Seasonal storage profile
Each calendar month's reference average, against the most recent year
Seasonal storage profileSeasonal storage profile: 1991–2020 average, Most recent 12 months in Mm³, from 1 to 12.05001,0001,5002,000Mm³123456789101112Month1991–2020 average 1: 1,292 Mm³1991–2020 average 2: 1,518 Mm³1991–2020 average 3: 1,739 Mm³1991–2020 average 4: 1,865 Mm³1991–2020 average 5: 1,834 Mm³1991–2020 average 6: 1,690 Mm³1991–2020 average 7: 1,280 Mm³1991–2020 average 8: 807 Mm³1991–2020 average 9: 483 Mm³1991–2020 average 10: 478 Mm³1991–2020 average 11: 766 Mm³1991–2020 average 12: 1,056 Mm³Most recent 12 months 1: 1,076 Mm³Most recent 12 months 2: 1,343 Mm³Most recent 12 months 3: 1,582 Mm³Most recent 12 months 4: 1,670 Mm³Most recent 12 months 5: 1,346 Mm³Most recent 12 months 6: 930 Mm³Most recent 12 months 7: 539 Mm³Most recent 12 months 8: 253 Mm³Most recent 12 months 9: 108 Mm³Most recent 12 months 10: 175 Mm³Most recent 12 months 11: 473 Mm³Most recent 12 months 12: 761 Mm³
  • 1991–2020 average
  • Most recent 12 months

Twelve separate averages, one per calendar month. A January average describes Januaries only. Months are plotted 1–12.

View the data behind this chart
Underlying data
Period1991–2020 average (Mm³)Most recent 12 months (Mm³)
Jan1,2921,076
Feb1,5181,343
Mar1,7391,582
Apr1,8651,670
May1,8341,346
Jun1,690930
Jul1,280539
Aug807253
Sep483108
Oct478175
Nov766473
Dec1,056761

Why this page shows a volume and not a percentage

Water level

Monthly mean water surface elevation
1,211 monthly values
Monthly mean water surface elevationMonthly mean water surface elevation: American Falls Reservoir in m, from 1925.75 to 2026.5833333333333.1,3101,3201,330m1925.751938.41666666666671951.08333333333331963.751976.41666666666671989.08333333333332001.752014.4166666666667Year

An elevation above a datum, not a depth of water and not a distance below the crest. Levels at different reservoirs are measured against different datums and must not be read against one another; this line is comparable only with its own history. Elevation and volume are not proportional either — a metre near the bottom of a reservoir holds far less water than a metre near the top, because the surface area grows with height.

What the shaded periods are (0 events)

Not shown on this chart

  • The 1976 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • The 2022 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • Yorkshire drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • Cantareira water crisis, São Paulo — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • Cape Town Day Zero — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
  • European drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
View the data behind this chart
240 of 1,211 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,211 would be longer than this page and unusable with a screen reader.
PeriodAmerican Falls Reservoir (m)
1925.751,310
1926.16666666666671,310
1926.58333333333331,311
19271,319
1927.41666666666671,327
1927.83333333333331,327
1928.251,325
1928.66666666666671,324
1929.16666666666671,326
1929.58333333333331,324
19301,322
1930.41666666666671,324
1930.83333333333331,323
1931.251,326
1931.66666666666671,312
1932.08333333333331,318
1932.51,324
1932.91666666666671,320
1933.33333333333331,325
1933.751,317
1934.16666666666671,324
1934.58333333333331,315
19351,317
1935.41666666666671,323
1935.91666666666671,318
1936.33333333333331,327
1936.751,320
1937.16666666666671,327
1937.58333333333331,322
19381,324
1938.41666666666671,327
1938.83333333333331,324
1939.251,327
1939.66666666666671,317
1940.08333333333331,325
1940.51,322
1940.91666666666671,322
1941.33333333333331,327
1941.751,318
1942.16666666666671,326
1942.66666666666671,319
1943.08333333333331,325
1943.51,327
1943.91666666666671,325
1944.33333333333331,327
1944.751,320
1945.16666666666671,327
1945.58333333333331,325
19461,325
1946.41666666666671,327
1946.83333333333331,324
1947.251,327
1947.66666666666671,321
1948.08333333333331,326
1948.51,327
1948.91666666666671,324
1949.41666666666671,327
1949.83333333333331,322
1950.251,326
1950.66666666666671,323
1951.08333333333331,326
1951.51,327
1951.91666666666671,326
1952.33333333333331,327
1952.751,320
1953.16666666666671,327
1953.58333333333331,323
19541,325
1954.41666666666671,327
1954.83333333333331,323
1955.251,327
1955.66666666666671,318
1956.16666666666671,326
1956.58333333333331,324
19571,325
1957.41666666666671,327
1957.83333333333331,321
1958.251,327
1958.66666666666671,317
1959.08333333333331,325
1959.51,321
1959.91666666666671,321
1960.33333333333331,326
1960.751,312
1961.16666666666671,326
1961.58333333333331,314
19621,324
1962.41666666666671,327
1962.91666666666671,321
1963.33333333333331,328
1963.751,317
1964.16666666666671,326
1964.58333333333331,324
19651,324
1965.41666666666671,327
1965.83333333333331,324
1966.251,326
1966.66666666666671,312
1967.08333333333331,325
1967.51,327
1967.91666666666671,323
1968.33333333333331,327
1968.751,321
1969.16666666666671,325
1969.66666666666671,316
1970.08333333333331,325
1970.51,327
1970.91666666666671,324
1971.33333333333331,327
1971.751,325
1972.16666666666671,325
1972.58333333333331,324
19731,324
1973.41666666666671,323
1973.83333333333331,318
1974.251,324
1974.66666666666671,317
1975.08333333333331,323
1975.51,323
1975.91666666666671,322
1976.41666666666671,324
1976.83333333333331,318
1977.251,324
1977.66666666666671,309
1978.08333333333331,324
1978.51,326
1978.91666666666671,323
1979.33333333333331,327
1979.751,314
1980.16666666666671,326
1980.58333333333331,323
19811,325
1981.41666666666671,327
1981.83333333333331,318
1982.251,327
1982.66666666666671,324
1983.16666666666671,326
1983.58333333333331,326
19841,324
1984.41666666666671,327
1984.83333333333331,325
1985.251,326
1985.66666666666671,318
1986.08333333333331,324
1986.51,327
1986.91666666666671,323
1987.33333333333331,326
1987.751,315
1988.16666666666671,326
1988.58333333333331,316
19891,322
1989.41666666666671,326
1989.91666666666671,320
1990.33333333333331,325
1990.751,314
1991.16666666666671,326
1991.58333333333331,319
19921,323
1992.41666666666671,322
1992.83333333333331,317
1993.251,327
1993.66666666666671,321
1994.08333333333331,326
1994.51,320
1994.91666666666671,320
1995.33333333333331,327
1995.751,321
1996.16666666666671,326
1996.66666666666671,322
1997.08333333333331,326
1997.51,327
1997.91666666666671,324
1998.33333333333331,327
1998.751,323
1999.16666666666671,326
1999.58333333333331,324
20001,324
2000.41666666666671,326
2000.83333333333331,319
2001.251,327
2001.66666666666671,313
2002.08333333333331,323
2002.51,320
2002.91666666666671,320
2003.41666666666671,322
2003.83333333333331,317
2004.251,325
2004.66666666666671,313
2005.08333333333331,324
2005.51,323
2005.91666666666671,321
2006.33333333333331,327
2006.751,318
2007.16666666666671,327
2007.58333333333331,315
20081,322
2008.41666666666671,325
2008.83333333333331,320
2009.251,327
2009.66666666666671,321
2010.16666666666671,327
2010.58333333333331,322
20111,324
2011.41666666666671,327
2011.83333333333331,322
2012.251,327
2012.66666666666671,315
2013.08333333333331,325
2013.51,320
2013.91666666666671,320
2014.33333333333331,327
2014.751,318
2015.16666666666671,326
2015.58333333333331,319
20161,322
2016.41666666666671,324
2016.91666666666671,321
2017.33333333333331,327
2017.751,323
2018.16666666666671,326
2018.58333333333331,321
20191,325
2019.41666666666671,327
2019.83333333333331,320
2020.251,327
2020.66666666666671,319
2021.08333333333331,325
2021.51,317
2021.91666666666671,321
2022.33333333333331,325
2022.751,314
2023.16666666666671,324
2023.66666666666671,317
2024.08333333333331,325
2024.51,324
2024.91666666666671,322
2025.33333333333331,327
2025.751,314
2026.16666666666671,325
2026.58333333333331,315

Rate and persistence

-6.15 Mm³
Mean drawdown per month over 12 months
10 of 24
Recent months below the 20th percentile for their own month

Rates are computed only across an unbroken run of months, so a rate is never divided by a period in which some of the change was not observed. Percentile counts compare each month with the same calendar month in every other year held.

Location

American Falls Reservoir
Gauge location
American Falls ReservoirAmerican Falls Reservoir — 252.98 Mm³American Falls Reservoir — 252.98 Mm³

About this data

About this data

Everything below is a property of the data rather than a rating of it. There is deliberately no single confidence score: how much a gap matters depends on what you are about to do with the series, and only you know that.

Source
United States Bureau of Reclamation — Reservoir operations and Colorado River data · US Government work — public domain
How the values came to existMeasured
Period held1925–2026
Completeness98.9% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps
  • Storage is a managed quantity. A falling line can be a rule curve, a scheduled release or a transfer to another system rather than a shortage of water, and nothing here distinguishes them.
  • No capacity figure on a stated basis is held for this reservoir, so no percentage of capacity is computed.
Continuity99% of the months between 1925 and 2026 are held. Monthly means of the publisher's own daily record.
Last read from the publisher2026-09-01
RedistributionPermitted by the upstream licences
Commercial reusePermitted by the upstream licences. No Hydrionis access tier can widen this.
MethodologyHow this was produced

Use this data

Use this data

No bulk download is offered here, which is a licence position rather than a product one: at least one contributing publisher does not permit redistribution. The values can be read on the page, cited, and pointed to at source.

Attribution and citation

Suggested citation for Hydrionis

Hydrionis (2026), American Falls Reservoir reservoir records, accessed 2026-09-02, hydrionis.com/reservoirs/reservoir-usbr-7167/

Cite Hydrionis where you rely on the compilation, the normalisation, the eligibility judgements or a chart. Where you use an unmodified published value, the publisher’s attribution is the one that is required; crediting Hydrionis as well is welcome and is not something Hydrionis can require of you.

Recommended, not required. Hydrionis does not claim rights over unmodified public data it relayed, and doing arithmetic on somebody else’s measurements does not make them Hydrionis’s. Cite the version and the access date: the American Falls Reservoir record changes as publishers release and as methods are revised, and a citation without both cannot be checked later. Full guidance is on cite and reuse.

None of the contributing licences requires attribution. Crediting the publishers is still good practice and they are listed above.

Where this comes from

1,211 monthly observations 1925–2026 Mm³
Spatially aggregatedHigh confidenceAugust 2026

Source: USBR — Reservoir operations and Colorado River data, RISE catalogue item 129132. Licence: Open.

Method: Monthly mean of the daily values published by the Bureau of Reclamation in acre-feet, converted to Mm³. Months with fewer than 20 days of record are not published rather than averaged from a partial month.

Stored as a volume and not as a share of capacity: the operator publishes what is in the reservoir but not what it holds when full, so a percentage cannot be computed without inventing the denominator.

Retrieved 1 September 2026.

Monthly mean of the daily values published by the Bureau of Reclamation in acre-feet, converted to Mm³. Months with fewer than 20 days of record are not published rather than averaged from a partial month.

Hydrionis would like to measure which pages are read, using Google Analytics. Google Analytics stores an identifier on your device, so we only do this if you agree. Nothing is measured if you decline, and the site works identically either way. See cookies for what is set and how to change your mind.