Gerber Reservoir — storage

Storage now, against this reservoir's own record

46.30 Mm³

Stored, August 2026

53rd

Percentile among 39 Augs on record

-14.7%

Against the Aug 1991–2020 average

-35.8%

Change over the 12 months to 2026-08

Storage in August 2026 was around the middle of the Aug record, ranked against 39 other Augs held for this reservoir.

Storage, 1986–2026

Monthly mean storage

401 monthly values, 1986 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 401 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 401 would be longer than this page and unusable with a screen reader.
Period	Gerber Reservoir (Mm³)
March 1986	117
May 1986	111
June 1986	101
August 1986	76.2
May 1987	75.0
June 1987	65.3
August 1987	45.8
April 1988	49.3
May 1988	47.9
July 1988	29.2
September 1988	9.49
May 1989	83.1
July 1989	61.4
September 1989	40.3
May 1990	51.1
July 1990	32.8
September 1990	13.4
May 1991	17.2
July 1991	5.32
May 1993	99.1
June 1993	94.2
August 1993	73.3
May 1994	58.2
June 1994	49.8
August 1994	26.9
April 1995	115
June 1995	111
July 1995	103
September 1995	78.8
March 1996	115
April 1996	119
June 1996	112
August 1996	91.4
September 1996	80.4
February 1997	112
May 1997	113
June 1997	104
August 1997	82.3
March 1998	114
April 1998	118
June 1998	118
August 1998	98.3
September 1998	87.6
April 1999	100
June 1999	105
July 1999	93.0
September 1999	71.3
November 1999	65.0
December 1999	65.5
February 2000	78.1
April 2000	110
May 2000	111
July 2000	90.1
September 2000	68.8
October 2000	64.0
December 2000	63.9
February 2001	64.4
March 2001	68.6
May 2001	69.1
July 2001	46.5
August 2001	35.7
October 2001	23.1
December 2001	24.5
January 2002	37.4
March 2002	52.4
May 2002	67.2
June 2002	56.7
August 2002	32.6
October 2002	17.5
November 2002	17.3
January 2003	24.2
March 2003	34.7
May 2003	62.3
June 2003	55.0
August 2003	31.1
October 2003	17.4
November 2003	17.1
January 2004	20.9
March 2004	50.4
April 2004	61.7
June 2004	48.0
August 2004	25.3
September 2004	15.8
November 2004	11.6
January 2005	17.3
February 2005	19.2
April 2005	31.2
June 2005	53.1
July 2005	43.0
September 2005	19.6
November 2005	17.3
December 2005	27.3
February 2006	88.2
April 2006	122
May 2006	117
July 2006	96.8
September 2006	73.9
October 2006	68.4
December 2006	72.3
February 2007	79.6
March 2007	95.0
May 2007	99.7
July 2007	77.6
August 2007	66.1
October 2007	51.3
December 2007	51.3
January 2008	52.8
March 2008	60.8
May 2008	96.3
June 2008	92.0
August 2008	69.7
October 2008	54.5
November 2008	54.3
January 2009	55.1
March 2009	65.1
April 2009	71.5
June 2009	63.0
August 2009	42.4
September 2009	32.1
November 2009	27.2
January 2010	29.2
March 2010	37.6
April 2010	41.3
June 2010	40.9
August 2010	19.6
September 2010	10.5
November 2010	6.81
January 2011	25.6
February 2011	35.0
April 2011	78.5
June 2011	88.7
July 2011	78.2
September 2011	57.0
November 2011	52.0
December 2011	52.0
February 2012	54.1
April 2012	75.4
May 2012	77.2
July 2012	57.6
September 2012	36.3
October 2012	31.8
December 2012	38.1
February 2013	43.5
March 2013	51.2
May 2013	53.4
July 2013	34.2
August 2013	24.2
October 2013	12.8
December 2013	12.5
January 2014	12.5
March 2014	20.2
May 2014	19.7
June 2014	11.2
August 2014	2.18
October 2014	1.61
November 2014	1.66
January 2015	14.3
March 2015	19.4
April 2015	19.7
June 2015	8.43
August 2015	2.13
September 2015	1.74
November 2015	1.52
January 2016	7.49
February 2016	29.6
April 2016	60.4
June 2016	47.7
July 2016	37.8
September 2016	18.4
November 2016	15.0
January 2017	24.6
February 2017	51.1
April 2017	112
June 2017	106
July 2017	95.2
September 2017	75.4
November 2017	71.3
December 2017	72.0
February 2018	77.3
April 2018	103
May 2018	101
July 2018	83.9
September 2018	64.6
October 2018	60.6
December 2018	60.3
February 2019	73.0
March 2019	87.5
May 2019	114
July 2019	94.9
August 2019	83.4
October 2019	72.6
December 2019	73.0
January 2020	75.6
March 2020	85.3
May 2020	80.4
June 2020	71.6
August 2020	50.2
October 2020	35.5
November 2020	32.2
January 2021	31.7
March 2021	34.5
April 2021	35.2
June 2021	20.9
August 2021	4.24
September 2021	2.61
November 2021	2.99
January 2022	4.40
February 2022	6.45
April 2022	15.6
June 2022	11.4
July 2022	3.90
September 2022	1.75
November 2022	1.56
December 2022	1.81
February 2023	11.5
April 2023	42.0
June 2023	51.3
July 2023	40.6
September 2023	21.3
November 2023	18.5
December 2023	18.8
February 2024	29.6
April 2024	50.0
May 2024	50.1
July 2024	29.3
September 2024	9.97
October 2024	7.83
December 2024	12.5
February 2025	40.1
March 2025	67.9
May 2025	106
July 2025	83.6
August 2025	72.1
October 2025	60.1
December 2025	61.6
January 2026	70.7
March 2026	80.2
May 2026	74.2
June 2026	66.7
August 2026	46.3

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	46.2	70.7
Feb	55.7	72.9
Mar	65.8	80.2
Apr	81.7	79.8
May	80.0	74.2
Jun	73.0	66.7
Jul	62.8	56.7
Aug	54.3	46.3
Sep	45.2	62.9
Oct	35.3	60.1
Nov	35.1	60.0
Dec	37.2	61.6

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

401 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 401 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 401 would be longer than this page and unusable with a screen reader.
Period	Gerber Reservoir (m)
1986.1666666666667	1,474
1986.3333333333333	1,474
1986.4166666666667	1,473
1986.5833333333333	1,471
1987.3333333333333	1,471
1987.4166666666667	1,470
1987.5833333333333	1,469
1988.25	1,469
1988.3333333333333	1,469
1988.5	1,467
1988.6666666666667	1,464
1989.3333333333333	1,472
1989.5	1,470
1989.6666666666667	1,468
1990.3333333333333	1,469
1990.5	1,467
1990.6666666666667	1,465
1991.3333333333333	1,466
1991.5	1,464
1993.3333333333333	1,473
1993.4166666666667	1,472
1993.5833333333333	1,471
1994.3333333333333	1,470
1994.4166666666667	1,469
1994.5833333333333	1,467
1995.25	1,474
1995.4166666666667	1,474
1995.5	1,473
1995.6666666666667	1,471
1996.1666666666667	1,474
1996.25	1,474
1996.4166666666667	1,474
1996.5833333333333	1,472
1996.6666666666667	1,471
1997.0833333333333	1,474
1997.3333333333333	1,474
1997.4166666666667	1,473
1997.5833333333333	1,471
1998.1666666666667	1,474
1998.25	1,474
1998.4166666666667	1,474
1998.5833333333333	1,473
1998.6666666666667	1,472
1999.25	1,473
1999.4166666666667	1,473
1999.5	1,472
1999.6666666666667	1,471
1999.8333333333333	1,470
1999.9166666666667	1,470
2000.0833333333333	1,471
2000.25	1,473
2000.3333333333333	1,474
2000.5	1,472
2000.6666666666667	1,470
2000.75	1,470
2000.9166666666667	1,470
2001.0833333333333	1,470
2001.1666666666667	1,470
2001.3333333333333	1,471
2001.5	1,469
2001.5833333333333	1,468
2001.75	1,466
2001.9166666666667	1,466
2002	1,468
2002.1666666666667	1,469
2002.3333333333333	1,470
2002.4166666666667	1,470
2002.5833333333333	1,467
2002.75	1,466
2002.8333333333333	1,466
2003	1,466
2003.1666666666667	1,468
2003.3333333333333	1,470
2003.4166666666667	1,469
2003.5833333333333	1,467
2003.75	1,466
2003.8333333333333	1,466
2004	1,466
2004.1666666666667	1,469
2004.25	1,470
2004.4166666666667	1,469
2004.5833333333333	1,467
2004.6666666666667	1,465
2004.8333333333333	1,465
2005	1,466
2005.0833333333333	1,466
2005.25	1,467
2005.4166666666667	1,469
2005.5	1,468
2005.6666666666667	1,466
2005.8333333333333	1,466
2005.9166666666667	1,467
2006.0833333333333	1,472
2006.25	1,474
2006.3333333333333	1,474
2006.5	1,473
2006.6666666666667	1,471
2006.75	1,470
2006.9166666666667	1,471
2007.0833333333333	1,471
2007.1666666666667	1,472
2007.3333333333333	1,473
2007.5	1,471
2007.5833333333333	1,470
2007.75	1,469
2007.9166666666667	1,469
2008	1,469
2008.1666666666667	1,470
2008.3333333333333	1,472
2008.4166666666667	1,472
2008.5833333333333	1,471
2008.75	1,469
2008.8333333333333	1,469
2009	1,469
2009.1666666666667	1,470
2009.25	1,471
2009.4166666666667	1,470
2009.5833333333333	1,468
2009.6666666666667	1,467
2009.8333333333333	1,467
2010	1,467
2010.1666666666667	1,468
2010.25	1,468
2010.4166666666667	1,468
2010.5833333333333	1,466
2010.6666666666667	1,465
2010.8333333333333	1,464
2011	1,467
2011.0833333333333	1,468
2011.25	1,471
2011.4166666666667	1,472
2011.5	1,471
2011.6666666666667	1,470
2011.8333333333333	1,469
2011.9166666666667	1,469
2012.0833333333333	1,469
2012.25	1,471
2012.3333333333333	1,471
2012.5	1,470
2012.6666666666667	1,468
2012.75	1,467
2012.9166666666667	1,468
2013.0833333333333	1,468
2013.1666666666667	1,469
2013.3333333333333	1,469
2013.5	1,467
2013.5833333333333	1,466
2013.75	1,465
2013.9166666666667	1,465
2014	1,465
2014.1666666666667	1,466
2014.3333333333333	1,466
2014.4166666666667	1,465
2014.5833333333333	1,463
2014.75	1,462
2014.8333333333333	1,462
2015	1,465
2015.1666666666667	1,466
2015.25	1,466
2015.4166666666667	1,464
2015.5833333333333	1,463
2015.6666666666667	1,463
2015.8333333333333	1,462
2016	1,464
2016.0833333333333	1,467
2016.25	1,470
2016.4166666666667	1,469
2016.5	1,468
2016.6666666666667	1,466
2016.8333333333333	1,465
2017	1,466
2017.0833333333333	1,469
2017.25	1,474
2017.4166666666667	1,473
2017.5	1,472
2017.6666666666667	1,471
2017.8333333333333	1,471
2017.9166666666667	1,471
2018.0833333333333	1,471
2018.25	1,473
2018.3333333333333	1,473
2018.5	1,472
2018.6666666666667	1,470
2018.75	1,470
2018.9166666666667	1,470
2019.0833333333333	1,471
2019.1666666666667	1,472
2019.3333333333333	1,474
2019.5	1,472
2019.5833333333333	1,472
2019.75	1,471
2019.9166666666667	1,471
2020	1,471
2020.1666666666667	1,472
2020.3333333333333	1,471
2020.4166666666667	1,471
2020.5833333333333	1,469
2020.75	1,468
2020.8333333333333	1,467
2021	1,467
2021.1666666666667	1,468
2021.25	1,468
2021.4166666666667	1,466
2021.5833333333333	1,463
2021.6666666666667	1,463
2021.8333333333333	1,463
2022	1,463
2022.0833333333333	1,464
2022.25	1,465
2022.4166666666667	1,465
2022.5	1,463
2022.6666666666667	1,463
2022.8333333333333	1,462
2022.9166666666667	1,462
2023.0833333333333	1,465
2023.25	1,468
2023.4166666666667	1,469
2023.5	1,468
2023.6666666666667	1,466
2023.8333333333333	1,466
2023.9166666666667	1,466
2024.0833333333333	1,467
2024.25	1,469
2024.3333333333333	1,469
2024.5	1,467
2024.6666666666667	1,465
2024.75	1,464
2024.9166666666667	1,465
2025.0833333333333	1,468
2025.1666666666667	1,470
2025.3333333333333	1,473
2025.5	1,472
2025.5833333333333	1,471
2025.75	1,470
2025.9166666666667	1,470
2026	1,471
2026.1666666666667	1,471
2026.3333333333333	1,471
2026.4166666666667	1,470
2026.5833333333333	1,469

Rate and persistence

-2.15 Mm³

Mean drawdown per month over 12 months

4 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

Gerber Reservoir

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	1986–2026
Completeness	81.5% 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	82% of the months between 1986 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-7306.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), Gerber Reservoir reservoir records, accessed 2026-09-02, hydrionis.com/reservoirs/reservoir-usbr-7306/

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 Gerber 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

401 monthly observations 1986–2026 Mm³

Spatially aggregatedHigh confidenceAugust 2026

Source: USBR — Reservoir operations and Colorado River data, RISE catalogue item 134034. 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.