Ochoco Reservoir — storage

Storage now, against this reservoir's own record

11.06 Mm³

Stored, September 2026

24th

Percentile among 43 Seps on record

-46.3%

Against the Sep 1991–2020 average

-66.0%

Change over the 12 months to 2026-09

Storage in September 2026 was lower than most Seps on record, ranked against 43 other Seps held for this reservoir.

Storage, 1969–2026

Monthly mean storage

519 monthly values, 1969 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 519 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 519 would be longer than this page and unusable with a screen reader.
Period	Ochoco Reservoir (Mm³)
November 1969	21.4
November 1974	24.9
November 1983	30.0
February 1984	41.1
April 1984	56.4
June 1984	57.2
August 1984	39.9
October 1984	28.3
December 1984	33.1
March 1985	32.2
May 1985	52.8
July 1985	39.5
September 1985	25.1
November 1985	22.3
January 1986	25.0
April 1986	57.2
June 1986	48.8
August 1986	29.9
October 1986	22.3
December 1986	24.6
February 1987	31.8
May 1987	54.5
July 1987	40.0
September 1987	25.9
November 1987	21.4
January 1988	23.7
March 1988	30.9
June 1988	26.9
August 1988	15.1
October 1988	1.28
December 1988	2.34
February 1989	7.36
April 1989	47.2
July 1989	37.8
September 1989	20.2
November 1989	10.5
January 1990	12.0
March 1990	16.0
May 1990	18.1
August 1990	6.24
October 1990	0.638
December 1990	0.923
February 1991	3.07
April 1991	6.89
June 1991	13.4
September 1991	2.43
November 1991	1.08
January 1992	6.16
March 1992	10.5
May 1992	13.4
July 1992	8.07
October 1992	0.518
December 1992	0.515
February 1993	3.75
April 1993	31.4
June 1993	30.9
August 1993	19.8
November 1993	12.0
January 1994	1.23
March 1994	0.286
May 1994	13.4
July 1994	8.07
September 1994	1.30
December 1994	0.515
February 1995	3.75
April 1995	30.8
June 1995	30.6
August 1995	15.0
October 1995	0.409
January 1996	9.10
March 1996	46.0
May 1996	53.3
July 1996	41.3
September 1996	25.6
November 1996	21.8
February 1997	45.2
April 1997	54.3
June 1997	52.1
August 1997	37.9
October 1997	30.0
December 1997	30.2
March 1998	42.3
May 1998	54.9
July 1998	49.4
September 1998	33.1
November 1998	27.7
January 1999	32.8
April 1999	34.5
June 1999	40.6
August 1999	25.4
October 1999	15.0
December 1999	15.0
February 2000	20.7
May 2000	51.2
July 2000	36.5
September 2000	24.2
November 2000	20.4
January 2001	21.1
March 2001	22.9
June 2001	23.4
August 2001	14.5
October 2001	9.53
December 2001	9.48
February 2002	17.6
April 2002	32.0
July 2002	23.7
September 2002	15.0
November 2002	12.1
January 2003	13.5
March 2003	26.0
May 2003	39.6
August 2003	23.5
October 2003	16.3
December 2003	16.3
February 2004	28.4
April 2004	53.1
June 2004	51.7
September 2004	34.9
November 2004	31.0
January 2005	31.1
March 2005	35.3
May 2005	47.5
July 2005	43.6
October 2005	27.3
December 2005	28.1
February 2006	35.7
April 2006	45.8
June 2006	51.8
August 2006	36.6
November 2006	27.5
January 2007	34.1
March 2007	47.0
May 2007	50.3
July 2007	36.5
September 2007	24.4
December 2007	22.6
February 2008	25.3
April 2008	42.6
June 2008	51.7
August 2008	36.3
October 2008	27.1
January 2009	27.8
March 2009	32.6
May 2009	43.1
July 2009	34.7
September 2009	22.4
November 2009	19.3
February 2010	25.4
April 2010	40.4
June 2010	52.8
August 2010	38.4
October 2010	29.2
December 2010	32.5
March 2011	43.8
May 2011	51.3
July 2011	48.8
September 2011	34.2
November 2011	30.4
January 2012	31.5
April 2012	51.3
June 2012	48.3
August 2012	32.2
October 2012	21.1
December 2012	22.2
February 2013	27.1
May 2013	36.6
July 2013	25.1
September 2013	13.6
November 2013	12.1
January 2014	12.5
March 2014	29.5
June 2014	38.2
August 2014	24.4
October 2014	18.6
December 2014	20.8
February 2015	35.3
April 2015	42.2
July 2015	25.9
September 2015	14.3
November 2015	12.2
January 2016	16.0
March 2016	46.6
May 2016	50.7
August 2016	33.1
October 2016	24.0
December 2016	24.2
February 2017	31.1
April 2017	51.2
June 2017	49.5
September 2017	26.0
November 2017	23.5
January 2018	24.4
March 2018	28.8
May 2018	34.4
July 2018	21.7
October 2018	6.82
December 2018	6.91
February 2019	7.86
April 2019	34.7
June 2019	45.8
August 2019	31.5
November 2019	24.6
January 2020	25.0
March 2020	28.2
May 2020	27.6
July 2020	19.4
September 2020	9.10
December 2020	7.18
February 2021	8.48
April 2021	13.8
June 2021	10.5
August 2021	5.05
October 2021	4.19
January 2022	4.40
March 2022	6.28
May 2022	11.4
July 2022	10.8
September 2022	5.56
November 2022	5.33
February 2023	6.47
April 2023	15.1
June 2023	38.0
August 2023	24.2
October 2023	17.4
December 2023	17.6
March 2024	42.5
May 2024	53.3
July 2024	43.0
September 2024	30.6
November 2024	27.9
January 2025	31.3
April 2025	50.3
June 2025	50.0
August 2025	36.6
October 2025	30.4
December 2025	29.9
February 2026	32.3
May 2026	30.0
July 2026	20.1
September 2026	11.1

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	20.8	31.2
Feb	24.3	32.3
Mar	31.1	34.9
Apr	38.4	33.9
May	41.3	30.0
Jun	39.2	25.5
Jul	32.9	20.1
Aug	25.7	14.9
Sep	20.6	11.1
Oct	17.9	30.4
Nov	17.6	29.9
Dec	18.7	29.9

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

506 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 506 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 506 would be longer than this page and unusable with a screen reader.
Period	Ochoco Reservoir (m)
1983.75	947
1983.9166666666667	948
1984.0833333333333	950
1984.25	954
1984.4166666666667	954
1984.6666666666667	947
1984.8333333333333	947
1985	948
1985.1666666666667	947
1985.3333333333333	953
1985.5	950
1985.6666666666667	945
1985.8333333333333	944
1986	945
1986.25	954
1986.4166666666667	952
1986.5833333333333	947
1986.75	944
1986.9166666666667	945
1987.0833333333333	947
1987.25	954
1987.4166666666667	952
1987.5833333333333	948
1987.8333333333333	944
1988	945
1988.1666666666667	947
1988.3333333333333	947
1988.5	943
1988.6666666666667	937
1988.8333333333333	930
1989	935
1989.25	952
1989.4166666666667	952
1989.5833333333333	946
1989.75	940
1989.9166666666667	939
1990.0833333333333	940
1990.25	943
1990.4166666666667	942
1990.5833333333333	936
1990.8333333333333	930
1991	931
1991.1666666666667	935
1991.3333333333333	939
1991.5	939
1991.6666666666667	932
1991.8333333333333	931
1992	936
1992.1666666666667	939
1992.4166666666667	939
1992.5833333333333	934
1992.75	930
1992.9166666666667	930
1993.0833333333333	934
1993.25	948
1993.4166666666667	948
1993.5833333333333	944
1993.75	941
1994	931
1994.1666666666667	930
1995.1666666666667	945
1995.3333333333333	949
1995.5	945
1995.6666666666667	937
1995.8333333333333	931
1996	938
1996.1666666666667	952
1996.4166666666667	953
1996.5833333333333	948
1996.75	945
1996.9166666666667	948
1997.0833333333333	952
1997.25	954
1997.4166666666667	954
1997.5833333333333	950
1997.75	948
1998	948
1998.1666666666667	951
1998.3333333333333	954
1998.5	953
1998.6666666666667	949
1998.8333333333333	947
1999	948
1999.1666666666667	948
1999.3333333333333	951
1999.5833333333333	946
1999.75	942
1999.9166666666667	942
2000.0833333333333	944
2000.25	953
2000.4166666666667	952
2000.5833333333333	947
2000.75	944
2001	945
2001.1666666666667	945
2001.3333333333333	947
2001.5	943
2001.6666666666667	940
2001.8333333333333	939
2002	941
2002.1666666666667	945
2002.3333333333333	949
2002.5833333333333	943
2002.75	941
2002.9166666666667	940
2003.0833333333333	945
2003.25	949
2003.4166666666667	950
2003.5833333333333	945
2003.75	943
2003.9166666666667	943
2004.1666666666667	951
2004.3333333333333	954
2004.5	952
2004.6666666666667	949
2004.8333333333333	948
2005	948
2005.1666666666667	949
2005.3333333333333	953
2005.5	951
2005.75	947
2005.9166666666667	947
2006.0833333333333	949
2006.25	952
2006.4166666666667	954
2006.5833333333333	950
2006.75	947
2006.9166666666667	948
2007.0833333333333	950
2007.3333333333333	953
2007.5	950
2007.6666666666667	946
2007.8333333333333	945
2008	945
2008.1666666666667	949
2008.3333333333333	953
2008.5	952
2008.6666666666667	948
2008.9166666666667	947
2009.0833333333333	947
2009.25	950
2009.4166666666667	951
2009.5833333333333	947
2009.75	944
2009.9166666666667	944
2010.0833333333333	946
2010.25	951
2010.5	952
2010.6666666666667	948
2010.8333333333333	947
2011	950
2011.1666666666667	952
2011.3333333333333	953
2011.5	953
2011.6666666666667	949
2011.9166666666667	948
2012.0833333333333	949
2012.25	953
2012.4166666666667	953
2012.5833333333333	948
2012.75	945
2012.9166666666667	945
2013.0833333333333	947
2013.25	951
2013.5	946
2013.6666666666667	941
2013.8333333333333	941
2014	941
2014.1666666666667	947
2014.3333333333333	951
2014.5	948
2014.6666666666667	944
2014.8333333333333	943
2015.0833333333333	949
2015.25	951
2015.4166666666667	949
2015.5833333333333	944
2015.75	941
2015.9166666666667	941
2016.0833333333333	948
2016.25	954
2016.4166666666667	952
2016.6666666666667	947
2016.8333333333333	946
2017	946
2017.1666666666667	951
2017.3333333333333	954
2017.5	951
2017.6666666666667	946
2017.8333333333333	945
2018	946
2018.25	949
2018.4166666666667	947
2018.5833333333333	942
2018.75	937
2018.9166666666667	938
2019.0833333333333	938
2019.25	949
2019.4166666666667	952
2019.5833333333333	948
2019.8333333333333	946
2020	946
2020.1666666666667	947
2020.3333333333333	947
2020.5	944
2020.6666666666667	939
2020.8333333333333	938
2021	938
2021.1666666666667	940
2021.4166666666667	940
2021.5833333333333	936
2021.75	935
2021.9166666666667	935
2022.0833333333333	936
2022.25	939
2022.4166666666667	940
2022.5833333333333	938
2022.8333333333333	936
2023	937
2023.1666666666667	938
2023.3333333333333	949
2023.5	948
2023.6666666666667	944
2023.8333333333333	943
2024	944
2024.1666666666667	951
2024.4166666666667	953
2024.5833333333333	949
2024.75	947
2024.9166666666667	947
2025.0833333333333	948
2025.25	953
2025.4166666666667	953
2025.5833333333333	950
2025.75	948
2026	948
2026.1666666666667	949
2026.3333333333333	948
2026.5	944
2026.6666666666667	940

Rate and persistence

-1.78 Mm³

Mean drawdown per month over 12 months

2 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

Ochoco 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	1969–2026
Completeness	74.6% 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	75% of the months between 1969 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-3665.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), Ochoco Reservoir reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usbr-3665/

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 Ochoco 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

519 monthly observations 1969–2026 Mm³

Spatially aggregatedHigh confidenceSeptember 2026

Source: USBR — Reservoir operations and Colorado River data, RISE catalogue item 132075. 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.