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

89.09 Mm³
Stored, September 2026
14th
Percentile among 101 Seps on record
-81.5%
Against the Sep 1991–2020 average
-17.8%
Change over the 12 months to 2026-09

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

Storage, 1925–2026

Monthly mean storage
1,212 monthly values, 1925 to 2026
Monthly mean storageMonthly mean storage: American Falls Reservoir in Mm³, from 1925.75 to 2026.6666666666667.01,0002,000Mm³1925.751938.41666666666671951.08333333333331963.751976.41666666666671989.08333333333332001.752014.4166666666667Year

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 1,212 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,212 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
July 1935761
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
November 1941897
April 19422,045
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
March 19481,941
August 19481,320
January 19491,431
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
July 19541,959
December 19541,338
May 19552,065
October 1955392
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
November 1960333
April 19611,915
September 196143.5
February 19621,733
July 19621,655
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
March 19671,840
August 19671,363
January 19681,396
June 19682,024
November 19681,174
April 19691,924
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
July 1973883
December 1973899
May 19741,475
October 1974379
March 19751,344
August 19751,042
January 19761,103
June 19761,387
November 1976531
April 19771,332
September 19771.74
February 19781,357
July 19781,854
December 19781,268
June 19791,716
November 1979389
April 19802,048
September 1980891
February 19811,728
July 19811,611
December 1981819
May 19822,042
October 19821,563
March 19831,815
August 19831,788
January 19841,365
June 19842,087
November 19841,494
April 19851,822
October 1985535
March 19861,671
August 19861,666
January 19871,234
June 19871,647
November 1987516
April 19881,999
September 198859.6
February 19891,234
July 19891,090
December 1989765
May 19901,586
October 1990126
March 19911,689
August 1991645
February 19921,444
July 1992623
December 1992730
May 19932,053
October 1993772
March 19942,025
August 1994320
January 19951,120
June 19952,077
November 19951,152
April 19961,684
September 1996967
February 19971,675
July 19971,961
December 19971,350
June 19982,061
November 19981,429
April 19991,895
September 1999968
February 20001,577
July 20001,223
December 2000901
May 20011,761
October 2001131
March 20021,544
August 2002283
January 2003998
June 20031,029
November 2003349
April 20041,538
October 2004179
March 20051,589
August 2005658
January 20061,241
June 20061,927
November 2006825
April 20072,045
September 200734.1
February 20081,240
July 20081,175
December 20081,052
May 20092,029
October 2009827
March 20101,977
August 20101,084
February 20111,448
July 20112,058
December 20111,106
May 20121,879
October 2012241
March 20131,811
August 2013292
January 20141,025
June 20141,505
November 2014745
April 20151,804
September 2015198
February 20161,263
July 2016834
December 2016932
June 20172,050
November 20171,482
April 20181,941
September 2018501
February 20191,821
July 20191,430
December 20191,087
May 20202,061
October 2020531
March 20211,875
August 2021297
January 20221,061
June 20221,291
November 2022408
April 20231,674
October 2023404
March 20241,924
August 2024847
January 20251,271
June 20251,466
November 2025473
April 20261,670
September 202689.1

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: 249 Mm³Most recent 12 months 9: 89.1 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
Aug807249
Sep48389.1
Oct478175
Nov766473
Dec1,056761

Why this page shows a volume and not a percentage

Water level

Monthly mean water surface elevation
1,212 monthly values
Monthly mean water surface elevationMonthly mean water surface elevation: American Falls Reservoir in m, from 1925.75 to 2026.6666666666667.1,3101,3201,330m1925.751938.41666666666671951.08333333333331963.751976.41666666666671989.08333333333332001.752014.4166666666667Year

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 1,212 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,212 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
1935.51,320
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
1941.83333333333331,321
1942.251,327
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
1948.16666666666671,327
1948.58333333333331,324
19491,324
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
1954.51,327
1954.91666666666671,324
1955.33333333333331,327
1955.751,317
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
1960.83333333333331,316
1961.251,327
1961.66666666666671,312
1962.08333333333331,326
1962.51,325
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
1967.16666666666671,326
1967.58333333333331,324
19681,324
1968.41666666666671,327
1968.83333333333331,323
1969.251,326
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
1973.51,321
1973.91666666666671,321
1974.33333333333331,324
1974.751,316
1975.16666666666671,324
1975.58333333333331,322
19761,322
1976.41666666666671,324
1976.83333333333331,318
1977.251,324
1977.66666666666671,309
1978.08333333333331,324
1978.51,326
1978.91666666666671,323
1979.41666666666671,326
1979.83333333333331,317
1980.251,327
1980.66666666666671,321
1981.08333333333331,326
1981.51,325
1981.91666666666671,321
1982.33333333333331,327
1982.751,325
1983.16666666666671,326
1983.58333333333331,326
19841,324
1984.41666666666671,327
1984.83333333333331,325
1985.251,326
1985.751,318
1986.16666666666671,326
1986.58333333333331,325
19871,323
1987.41666666666671,325
1987.83333333333331,318
1988.251,327
1988.66666666666671,313
1989.08333333333331,323
1989.51,322
1989.91666666666671,320
1990.33333333333331,325
1990.751,314
1991.16666666666671,326
1991.58333333333331,319
1992.08333333333331,324
1992.51,319
1992.91666666666671,320
1993.33333333333331,327
1993.751,320
1994.16666666666671,327
1994.58333333333331,316
19951,323
1995.41666666666671,327
1995.83333333333331,323
1996.251,326
1996.66666666666671,322
1997.08333333333331,326
1997.51,327
1997.91666666666671,324
1998.41666666666671,327
1998.83333333333331,324
1999.251,327
1999.66666666666671,322
2000.08333333333331,325
2000.51,323
2000.91666666666671,321
2001.33333333333331,326
2001.751,314
2002.16666666666671,325
2002.58333333333331,316
20031,322
2003.41666666666671,322
2003.83333333333331,317
2004.251,325
2004.751,315
2005.16666666666671,325
2005.58333333333331,319
20061,323
2006.41666666666671,327
2006.83333333333331,321
2007.251,327
2007.66666666666671,312
2008.08333333333331,323
2008.51,323
2008.91666666666671,322
2009.33333333333331,327
2009.751,321
2010.16666666666671,327
2010.58333333333331,322
2011.08333333333331,324
2011.51,327
2011.91666666666671,323
2012.33333333333331,326
2012.751,315
2013.16666666666671,326
2013.58333333333331,316
20141,322
2014.41666666666671,325
2014.83333333333331,320
2015.251,326
2015.66666666666671,315
2016.08333333333331,323
2016.51,321
2016.91666666666671,321
2017.41666666666671,327
2017.83333333333331,325
2018.251,327
2018.66666666666671,318
2019.08333333333331,326
2019.51,324
2019.91666666666671,322
2020.33333333333331,327
2020.751,318
2021.16666666666671,326
2021.58333333333331,316
20221,322
2022.41666666666671,324
2022.83333333333331,317
2023.251,326
2023.751,317
2024.16666666666671,327
2024.58333333333331,321
20251,323
2025.41666666666671,324
2025.83333333333331,318
2026.251,325
2026.66666666666671,313

Rate and persistence

-1.61 Mm³
Mean drawdown per month over 12 months
11 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 — 89.09 Mm³American Falls Reservoir — 89.09 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
Completeness99.0% 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 publisher2026-10-01
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 2026-10-05, 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

1,212 monthly observations 1925–2026 Mm³
Spatially aggregatedHigh confidenceSeptember 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 October 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.

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