Lake Mead — storage

Storage now, against this reservoir's own record

8,589.83 Mm³

Stored, August 2026

0th

Percentile among 90 Augs on record

-55.3%

Against the Aug 1991–2020 average

-13.2%

Change over the 12 months to 2026-08

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

Storage, 1937–2026

Monthly mean storage

1,071 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 1,071 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,071 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
August 1945	31,273
January 1946	27,854
May 1946	26,654
October 1946	27,089
February 1947	24,851
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
March 1954	19,589
August 1954	17,997
December 1954	16,010
May 1955	14,173
September 1955	15,155
February 1956	13,726
June 1956	16,323
November 1956	15,162
March 1957	14,342
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
January 1962	22,160
June 1962	28,072
October 1962	29,039
March 1963	27,386
July 1963	23,594
December 1963	20,082
April 1964	18,000
September 1964	14,624
January 1965	13,820
June 1965	17,375
October 1965	18,167
March 1966	19,155
July 1966	19,021
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
November 1969	20,124
April 1970	20,431
August 1970	20,413
January 1971	20,766
May 1971	20,149
October 1971	20,886
February 1972	22,052
July 1972	20,964
November 1972	22,147
April 1973	25,280
August 1973	25,436
January 1974	24,595
May 1974	23,285
October 1974	23,855
February 1975	24,619
July 1975	24,158
November 1975	24,823
April 1976	24,895
August 1976	24,629
January 1977	26,655
May 1977	25,041
October 1977	24,924
February 1978	26,064
June 1978	25,639
November 1978	26,070
March 1979	28,576
August 1979	27,460
December 1979	27,817
May 1980	28,434
September 1980	29,122
February 1981	29,052
June 1981	27,411
November 1981	27,353
March 1982	28,564
August 1982	27,677
December 1982	29,514
May 1983	30,368
September 1983	31,992
February 1984	29,843
June 1984	30,325
November 1984	29,800
March 1985	29,486
August 1985	30,744
December 1985	29,614
April 1986	28,924
September 1986	29,746
January 1987	30,153
June 1987	29,342
October 1987	29,995
March 1988	30,329
July 1988	28,657
December 1988	28,170
April 1989	28,087
September 1989	26,476
January 1990	26,631
June 1990	25,288
October 1990	24,751
March 1991	24,751
July 1991	23,895
December 1991	23,636
April 1992	24,869
September 1992	23,900
January 1993	24,814
June 1993	26,384
October 1993	26,305
March 1994	26,472
July 1994	24,694
November 1994	24,287
April 1995	25,002
August 1995	25,055
January 1996	26,896
May 1996	26,864
October 1996	26,752
February 1997	27,512
July 1997	28,845
November 1997	30,346
April 1998	30,745
August 1998	30,706
January 1999	30,545
May 1999	29,667
October 1999	30,486
February 2000	30,877
July 2000	28,628
November 2000	27,638
April 2001	26,981
August 2001	24,893
January 2002	24,482
May 2002	22,500
September 2002	21,146
February 2003	20,837
June 2003	19,508
November 2003	19,022
March 2004	18,930
August 2004	17,264
December 2004	17,712
May 2005	19,389
September 2005	18,889
February 2006	19,043
June 2006	17,685
November 2006	17,264
March 2007	17,418
August 2007	15,506
December 2007	15,673
May 2008	15,165
September 2008	14,760
February 2009	15,482
June 2009	13,721
November 2009	13,461
March 2010	14,379
July 2010	12,915
December 2010	12,472
April 2011	13,761
September 2011	15,848
January 2012	18,504
June 2012	16,501
October 2012	16,262
March 2013	16,834
July 2013	15,084
December 2013	15,178
April 2014	14,254
September 2014	12,482
January 2015	13,248
June 2015	11,888
October 2015	12,207
March 2016	12,596
July 2016	11,552
December 2016	12,168
April 2017	13,022
September 2017	12,512
January 2018	12,858
June 2018	12,182
October 2018	12,237
February 2019	13,004
July 2019	12,750
November 2019	12,673
April 2020	14,199
August 2020	12,764
January 2021	12,853
May 2021	11,974
October 2021	11,100
February 2022	11,057
July 2022	8,736
November 2022	8,975
April 2023	9,201
August 2023	10,691
January 2024	11,378
May 2024	11,303
October 2024	10,681
February 2025	11,124
July 2025	9,888
November 2025	10,163
April 2026	10,316
August 2026	8,590

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	8,590
Sep	19,241	10,073
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

1,099 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 1,099 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,099 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
1943.0833333333333	360
1943.5	366
1943.9166666666667	360
1944.25	353
1944.6666666666667	363
1945	355
1945.4166666666667	356
1945.8333333333333	357
1946.1666666666667	350
1946.5833333333333	354
1946.9166666666667	351
1947.3333333333333	348
1947.75	359
1948.0833333333333	354
1948.5	363
1948.8333333333333	358
1949.25	349
1949.6666666666667	363
1950	355
1950.4166666666667	356
1950.75	356
1951.1666666666667	349
1951.5833333333333	356
1951.9166666666667	352
1952.3333333333333	353
1952.6666666666667	364
1953.0833333333333	353
1953.5	355
1953.8333333333333	351
1954.25	345
1954.5833333333333	342
1955	336
1955.3333333333333	333
1955.75	334
1956.1666666666667	331
1956.5	340
1956.9166666666667	335
1957.25	332
1957.6666666666667	361
1958.0833333333333	357
1958.4166666666667	366
1958.8333333333333	363
1959.1666666666667	359
1959.5833333333333	359
1960	355
1960.3333333333333	357
1960.75	356
1961.0833333333333	354
1961.5	354
1961.9166666666667	352
1962.25	353
1962.6666666666667	365
1963	363
1963.4166666666667	357
1963.8333333333333	348
1964.1666666666667	343
1964.5833333333333	336
1964.9166666666667	332
1965.3333333333333	336
1965.75	343
1966.0833333333333	345
1966.5	345
1966.8333333333333	344
1967.25	345
1967.6666666666667	344
1968	345
1968.4166666666667	346
1968.75	346
1969.1666666666667	347
1969.5	348
1969.9166666666667	351
1970.3333333333333	351
1970.6666666666667	351
1971.0833333333333	351
1971.4166666666667	350
1971.8333333333333	352
1972.25	352
1972.5833333333333	352
1973	357
1973.3333333333333	362
1973.75	360
1974.1666666666667	359
1974.5	357
1974.9166666666667	359
1975.25	358
1975.6666666666667	359
1976.0833333333333	360
1976.4166666666667	360
1976.8333333333333	361
1977.1666666666667	363
1977.5833333333333	359
1978	361
1978.3333333333333	361
1978.75	361
1979.0833333333333	366
1979.5	364
1979.9166666666667	365
1980.25	366
1980.6666666666667	367
1981	367
1981.4166666666667	364
1981.75	364
1982.1666666666667	366
1982.5833333333333	365
1982.9166666666667	368
1983.3333333333333	369
1983.6666666666667	372
1984.0833333333333	368
1984.5	370
1984.8333333333333	368
1985.25	368
1985.5833333333333	370
1986	367
1986.4166666666667	369
1986.75	368
1987.1666666666667	369
1987.5	368
1987.9166666666667	369
1988.3333333333333	368
1988.6666666666667	366
1989.0833333333333	366
1989.4166666666667	363
1989.8333333333333	362
1990.25	362
1990.5833333333333	359
1991	359
1991.3333333333333	359
1991.75	357
1992.1666666666667	360
1992.5	358
1992.9166666666667	358
1993.25	364
1993.6666666666667	362
1994	363
1994.4166666666667	360
1994.8333333333333	359
1995.1666666666667	361
1995.5833333333333	360
1995.9166666666667	363
1996.3333333333333	363
1996.75	363
1997.0833333333333	364
1997.5	367
1997.8333333333333	369
1998.25	370
1998.6666666666667	370
1999	370
1999.4166666666667	368
1999.75	369
2000.1666666666667	370
2000.5833333333333	365
2000.9166666666667	365
2001.3333333333333	362
2001.6666666666667	359
2002.0833333333333	359
2002.5	353
2002.8333333333333	352
2003.25	351
2003.5833333333333	348
2004	347
2004.4166666666667	344
2004.75	343
2005.1666666666667	349
2005.5	347
2005.9166666666667	346
2006.3333333333333	346
2006.6666666666667	343
2007.0833333333333	344
2007.4166666666667	340
2007.8333333333333	339
2008.1666666666667	340
2008.5833333333333	337
2009	339
2009.3333333333333	335
2009.75	333
2010.0833333333333	336
2010.5	332
2010.9166666666667	330
2011.25	334
2011.6666666666667	340
2012	346
2012.4166666666667	341
2012.8333333333333	340
2013.1666666666667	342
2013.5833333333333	337
2013.9166666666667	337
2014.3333333333333	333
2014.75	330
2015.0833333333333	332
2015.5	328
2015.8333333333333	329
2016.25	329
2016.6666666666667	328
2017	330
2017.4166666666667	329
2017.75	330
2018.1666666666667	332
2018.5833333333333	329
2018.9166666666667	329
2019.3333333333333	332
2019.6666666666667	330
2020.0833333333333	334
2020.4166666666667	332
2020.8333333333333	330
2021.25	330
2021.5833333333333	325
2022	325
2022.3333333333333	320
2022.75	319
2023.1666666666667	319
2023.5	323
2023.9166666666667	325
2024.25	327
2024.6666666666667	324
2025.0833333333333	325
2025.4166666666667	322
2025.8333333333333	322
2026.1666666666667	324
2026.5833333333333	317

Rate and persistence

-109.08 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	99.2% 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	2026-09-01
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 2026-09-02, 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

1,071 monthly observations 1937–2026 Mm³

Spatially aggregatedHigh confidenceAugust 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 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.