Lake Mead — storage

Storage now, against this reservoir's own record

8,475.91 Mm³

Stored, September 2026

0th

Percentile among 90 Seps on record

-55.9%

Against the Sep 1991–2020 average

-15.9%

Change over the 12 months to 2026-09

Storage in September 2026 was lower than almost every other Sep on record, ranked against 90 other Seps held for this reservoir. It is the lowest in the held record for this month.

Storage, 1937–2026

Monthly mean storage

1,072 monthly values, 1937 to 2026

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 1,072 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,072 would be longer than this page and unusable with a screen reader.
Period	Lake Mead (Mm³)
June 1937	13,926
October 1937	14,775
March 1938	14,918
July 1938	24,814
December 1938	24,309
April 1939	23,171
September 1939	25,854
January 1940	24,273
June 1940	26,141
October 1940	25,260
March 1941	25,210
July 1941	34,007
December 1941	30,545
April 1942	26,333
September 1942	35,849
January 1943	31,858
June 1943	33,470
October 1943	33,119
March 1944	27,913
July 1944	34,271
December 1944	29,509
April 1945	25,920
September 1945	31,008
January 1946	27,854
June 1946	27,627
October 1946	27,089
March 1947	24,241
July 1947	30,163
November 1947	30,412
April 1948	27,094
August 1948	32,450
January 1949	27,989
May 1949	27,226
October 1949	26,727
February 1950	22,926
July 1950	25,593
November 1950	23,322
April 1951	20,517
August 1951	24,265
January 1952	21,754
May 1952	22,877
October 1952	27,223
February 1953	22,983
July 1953	23,950
November 1953	21,774
April 1954	19,099
August 1954	17,997
January 1955	15,428
May 1955	14,173
October 1955	14,716
February 1956	13,726
July 1956	17,021
November 1956	15,162
April 1957	14,006
August 1957	26,196
December 1957	26,063
May 1958	24,966
September 1958	29,030
February 1959	26,323
June 1959	25,438
November 1959	24,441
March 1960	23,534
August 1960	25,855
December 1960	23,957
May 1961	22,019
September 1961	22,115
February 1962	22,205
June 1962	28,072
November 1962	28,851
March 1963	27,386
August 1963	22,588
December 1963	20,082
May 1964	17,838
September 1964	14,624
February 1965	13,959
June 1965	17,375
November 1965	18,413
March 1966	19,155
August 1966	18,726
December 1966	18,979
April 1967	17,902
September 1967	17,613
January 1968	17,845
June 1968	18,402
October 1968	18,532
March 1969	18,980
July 1969	19,335
December 1969	20,517
April 1970	20,431
September 1970	20,592
January 1971	20,766
June 1971	20,231
October 1971	20,886
March 1972	21,552
July 1972	20,964
December 1972	22,645
April 1973	25,280
September 1973	25,021
January 1974	24,595
June 1974	23,140
October 1974	23,855
March 1975	24,499
July 1975	24,158
December 1975	24,785
April 1976	24,895
September 1976	24,543
January 1977	26,655
May 1977	25,041
October 1977	24,924
February 1978	26,064
July 1978	25,526
November 1978	26,070
April 1979	28,365
August 1979	27,460
January 1980	27,940
May 1980	28,434
October 1980	29,030
February 1981	29,052
July 1981	27,026
November 1981	27,353
April 1982	28,214
August 1982	27,677
January 1983	29,630
May 1983	30,368
October 1983	31,416
February 1984	29,843
July 1984	30,691
November 1984	29,800
April 1985	29,382
August 1985	30,744
January 1986	28,741
May 1986	29,328
October 1986	29,885
February 1987	30,212
June 1987	29,342
November 1987	29,951
March 1988	30,329
August 1988	28,350
December 1988	28,170
May 1989	27,371
September 1989	26,476
February 1990	26,750
June 1990	25,288
November 1990	24,619
March 1991	24,751
August 1991	23,740
December 1991	23,636
May 1992	24,633
September 1992	23,900
February 1993	25,961
June 1993	26,384
November 1993	26,206
March 1994	26,472
August 1994	24,643
December 1994	24,214
May 1995	24,690
September 1995	25,326
February 1996	27,162
June 1996	26,693
November 1996	26,879
March 1997	27,900
July 1997	28,845
December 1997	30,802
April 1998	30,745
September 1998	31,049
January 1999	30,545
June 1999	29,526
October 1999	30,486
March 2000	30,596
July 2000	28,628
December 2000	27,556
April 2001	26,981
September 2001	24,681
January 2002	24,482
June 2002	21,891
October 2002	21,043
March 2003	20,911
July 2003	19,327
December 2003	18,889
April 2004	18,603
September 2004	17,254
January 2005	18,168
June 2005	19,116
October 2005	18,668
March 2006	19,021
July 2006	17,387
November 2006	17,264
April 2007	16,878
August 2007	15,506
January 2008	15,966
May 2008	15,165
October 2008	14,989
February 2009	15,482
July 2009	13,609
November 2009	13,461
April 2010	14,096
August 2010	12,805
January 2011	12,959
May 2011	13,745
October 2011	16,342
February 2012	18,475
July 2012	16,240
November 2012	16,309
April 2013	16,276
August 2013	15,137
January 2014	15,336
May 2014	13,518
October 2014	12,557
February 2015	13,273
July 2015	11,960
November 2015	12,229
April 2016	12,172
August 2016	11,746
December 2016	12,168
May 2017	12,687
September 2017	12,512
February 2018	13,166
June 2018	12,182
November 2018	12,228
March 2019	13,319
August 2019	12,673
December 2019	13,083
May 2020	13,815
September 2020	12,735
February 2021	13,073
June 2021	11,425
November 2021	10,936
March 2022	10,788
August 2022	8,818
December 2022	8,931
May 2023	9,643
September 2023	10,979
February 2024	11,850
June 2024	10,823
November 2024	10,489
March 2025	11,109
August 2025	9,899
December 2025	10,476
May 2026	9,745
September 2026	8,476

The reservoir's year

Seasonal storage profile

Each calendar month's reference average, against the most recent year

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
Period	1991–2020 average (Mm³)	Most recent 12 months (Mm³)
Jan	20,156	10,762
Feb	20,388	10,941
Mar	20,398	10,823
Apr	20,104	10,316
May	19,686	9,745
Jun	19,362	9,208
Jul	19,197	8,808
Aug	19,196	8,587
Sep	19,241	8,476
Oct	19,282	10,178
Nov	19,325	10,163
Dec	19,462	10,476

Why this page shows a volume and not a percentage

Percentage full is a division, and the denominator is missing

“Percentage full” is the figure a drought is discussed in, and it is stored volume divided by capacity. Capacity is published on several different bases — gross, usable, live, and the figure at a particular spillway or licence condition — and dividing a stored volume by the wrong one produces a percentage confidently wrong by the ratio between them, at exactly the moment the number matters most.

Hydrionis holds storage measurements for this reservoir and does not hold a compatible authoritative capacity figure for it, so percentage full is not calculated. The volume above is what was actually measured. Where you need a percentage, take the publisher’s own capacity on its own stated basis and divide it yourself — the source is linked below, and knowing which basis you used is the whole point.

Water level

Monthly mean water surface elevation

1,100 monthly values

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 1,100 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,100 would be longer than this page and unusable with a screen reader.
Period	Lake Mead (m)
1935.0833333333333	212
1935.5	281
1935.8333333333333	278
1936.25	277
1936.5833333333333	312
1937	312
1937.4166666666667	332
1937.75	334
1938.1666666666667	335
1938.5	357
1938.9166666666667	356
1939.3333333333333	356
1939.6666666666667	359
1940.0833333333333	356
1940.4166666666667	360
1940.8333333333333	357
1941.25	357
1941.5833333333333	372
1942	363
1942.3333333333333	362
1942.75	366
1943.1666666666667	359
1943.5	366
1943.9166666666667	360
1944.25	353
1944.6666666666667	363
1945.0833333333333	353
1945.4166666666667	356
1945.8333333333333	357
1946.1666666666667	350
1946.5833333333333	354
1947	349
1947.3333333333333	348
1947.75	359
1948.0833333333333	354
1948.5	363
1948.9166666666667	356
1949.25	349
1949.6666666666667	363
1950	355
1950.4166666666667	356
1950.8333333333333	354
1951.1666666666667	349
1951.5833333333333	356
1951.9166666666667	352
1952.3333333333333	353
1952.75	362
1953.0833333333333	353
1953.5	355
1953.8333333333333	351
1954.25	345
1954.6666666666667	341
1955	336
1955.4166666666667	336
1955.75	334
1956.1666666666667	331
1956.5833333333333	339
1956.9166666666667	335
1957.3333333333333	335
1957.6666666666667	361
1958.0833333333333	357
1958.4166666666667	366
1958.8333333333333	363
1959.25	358
1959.5833333333333	359
1960	355
1960.3333333333333	357
1960.75	356
1961.1666666666667	353
1961.5	354
1961.9166666666667	352
1962.25	353
1962.6666666666667	365
1963.0833333333333	363
1963.4166666666667	357
1963.8333333333333	348
1964.1666666666667	343
1964.5833333333333	336
1965	332
1965.3333333333333	336
1965.75	343
1966.0833333333333	345
1966.5	345
1966.9166666666667	345
1967.25	345
1967.6666666666667	344
1968	345
1968.4166666666667	346
1968.8333333333333	347
1969.1666666666667	347
1969.5833333333333	349
1969.9166666666667	351
1970.3333333333333	351
1970.75	351
1971.0833333333333	351
1971.5	351
1971.8333333333333	352
1972.25	352
1972.6666666666667	353
1973	357
1973.4166666666667	362
1973.75	360
1974.1666666666667	359
1974.5833333333333	357
1974.9166666666667	359
1975.3333333333333	358
1975.6666666666667	359
1976.0833333333333	360
1976.5	360
1976.8333333333333	361
1977.25	362
1977.5833333333333	359
1978	361
1978.4166666666667	361
1978.75	361
1979.1666666666667	366
1979.5	364
1979.9166666666667	365
1980.3333333333333	366
1980.6666666666667	367
1981.0833333333333	367
1981.4166666666667	364
1981.8333333333333	364
1982.25	366
1982.5833333333333	365
1983	368
1983.3333333333333	369
1983.75	371
1984.1666666666667	368
1984.5	370
1984.9166666666667	368
1985.25	368
1985.6666666666667	370
1986.0833333333333	366
1986.4166666666667	369
1986.8333333333333	368
1987.1666666666667	369
1987.5833333333333	368
1988	369
1988.3333333333333	368
1988.75	366
1989.0833333333333	366
1989.5	363
1989.9166666666667	363
1990.25	362
1990.6666666666667	359
1991	359
1991.4166666666667	358
1991.8333333333333	357
1992.1666666666667	360
1992.5833333333333	358
1992.9166666666667	358
1993.3333333333333	363
1993.75	362
1994.0833333333333	363
1994.5	359
1994.8333333333333	359
1995.25	360
1995.6666666666667	361
1996	363
1996.4166666666667	363
1996.75	363
1997.1666666666667	365
1997.5833333333333	367
1997.9166666666667	370
1998.3333333333333	369
1998.6666666666667	370
1999.0833333333333	370
1999.5	368
1999.8333333333333	370
2000.25	369
2000.5833333333333	365
2001	365
2001.4166666666667	361
2001.75	359
2002.1666666666667	358
2002.5	353
2002.9166666666667	351
2003.3333333333333	349
2003.6666666666667	348
2004.0833333333333	348
2004.4166666666667	344
2004.8333333333333	344
2005.1666666666667	349
2005.5833333333333	347
2006	347
2006.3333333333333	346
2006.75	343
2007.0833333333333	344
2007.5	339
2007.9166666666667	339
2008.25	339
2008.6666666666667	337
2009	339
2009.4166666666667	334
2009.8333333333333	333
2010.1666666666667	336
2010.5833333333333	331
2010.9166666666667	330
2011.3333333333333	334
2011.75	341
2012.0833333333333	346
2012.5	340
2012.8333333333333	340
2013.25	340
2013.6666666666667	337
2014	338
2014.4166666666667	331
2014.75	330
2015.1666666666667	331
2015.5833333333333	329
2015.9166666666667	329
2016.3333333333333	328
2016.6666666666667	328
2017.0833333333333	332
2017.5	329
2017.8333333333333	330
2018.25	331
2018.5833333333333	329
2019	330
2019.4166666666667	331
2019.75	330
2020.1666666666667	334
2020.5	331
2020.9166666666667	330
2021.3333333333333	328
2021.6666666666667	325
2022.0833333333333	325
2022.4166666666667	319
2022.8333333333333	318
2023.25	319
2023.5833333333333	324
2024	326
2024.3333333333333	326
2024.75	324
2025.1666666666667	325
2025.5	321
2025.9166666666667	323
2026.25	323
2026.6666666666667	317

Rate and persistence

-133.11 Mm³

Mean drawdown per month over 12 months

24 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

Lake Mead

Gauge location

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 exist	Measured
Period held	1937–2026
Completeness	99.3% 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.
Continuity	99% of the months between 1937 and 2026 are held. Monthly means of the publisher's own daily record.
Last read from the publisher	2026-10-01
Redistribution	Permitted by the upstream licences
Commercial reuse	Permitted by the upstream licences. No Hydrionis access tier can widen this.
Methodology	How this was produced

Use this data

Machine-readable JSON /api/v1/observations/by-subject/reservoir-usbr-3514.json
How to cite this, and who you must credit
How these figures were produced
Request this at a different scale, format or geography

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), Lake Mead reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usbr-3514/

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 Lake Mead 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

1,072 monthly observations 1937–2026 Mm³

Spatially aggregatedHigh confidenceSeptember 2026

Source: USBR — Reservoir operations and Colorado River data, RISE catalogue item 6124. 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.