Lake Owyhee — storage

Storage now, against this reservoir's own record

140.10 Mm³

Stored, September 2026

14th

Percentile among 87 Seps on record

-56.4%

Against the Sep 1991–2020 average

-71.2%

Change over the 12 months to 2026-09

Storage in September 2026 was lower than most Seps on record, ranked against 87 other Seps held for this reservoir.

Storage, 1938–2026

Monthly mean storage

1,053 monthly values, 1938 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 1,053 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,053 would be longer than this page and unusable with a screen reader.
Period	Lake Owyhee (Mm³)
October 1938	592
February 1939	651
July 1939	671
November 1939	438
April 1940	839
August 1940	588
December 1940	529
May 1941	872
September 1941	615
February 1942	664
June 1942	876
October 1942	545
March 1943	743
July 1943	802
December 1943	563
April 1944	707
August 1944	562
January 1945	480
May 1945	882
October 1945	573
February 1946	711
June 1946	824
November 1946	494
March 1947	695
August 1947	445
December 1947	330
April 1948	548
September 1948	311
January 1949	329
June 1949	721
October 1949	399
February 1950	492
July 1950	677
November 1950	435
April 1951	882
August 1951	618
December 1951	516
May 1952	866
September 1952	601
February 1953	655
June 1953	780
October 1953	455
March 1954	623
July 1954	392
December 1954	185
April 1955	328
August 1955	193
January 1956	253
May 1956	844
October 1956	491
February 1957	614
June 1957	869
November 1957	519
March 1958	788
August 1958	679
December 1958	564
April 1959	637
September 1959	213
January 1960	267
June 1960	541
October 1960	201
March 1961	345
July 1961	213
November 1961	59.1
April 1962	431
August 1962	317
January 1963	258
May 1963	446
September 1963	317
February 1964	363
June 1964	803
November 1964	561
March 1965	774
July 1965	804
December 1965	667
April 1966	799
September 1966	355
January 1967	373
May 1967	577
October 1967	399
February 1968	486
July 1968	312
November 1968	174
March 1969	488
August 1969	654
December 1969	565
May 1970	875
September 1970	618
January 1971	793
June 1971	870
October 1971	578
March 1972	844
July 1972	776
November 1972	569
April 1973	879
August 1973	592
January 1974	575
May 1974	874
September 1974	506
February 1975	556
June 1975	877
November 1975	654
March 1976	817
July 1976	716
December 1976	569
April 1977	630
September 1977	233
January 1978	295
May 1978	885
October 1978	525
February 1979	683
July 1979	744
November 1979	531
March 1980	828
August 1980	699
December 1980	604
May 1981	750
September 1981	373
January 1982	494
June 1982	862
October 1982	599
March 1983	841
July 1983	830
November 1983	650
April 1984	829
August 1984	786
January 1985	716
May 1985	866
September 1985	511
February 1986	712
June 1986	854
November 1986	553
March 1987	674
July 1987	425
December 1987	195
April 1988	351
September 1988	14.9
January 1989	86.8
May 1989	865
October 1989	446
February 1990	531
July 1990	465
November 1990	218
March 1991	337
August 1991	180
December 1991	103
May 1992	144
December 1992	34.7
April 1993	882
September 1993	553
January 1994	534
June 1994	435
October 1994	55.9
February 1995	342
July 1995	796
November 1995	540
April 1996	860
August 1996	632
December 1996	511
May 1997	887
September 1997	567
February 1998	595
June 1998	891
October 1998	557
March 1999	712
July 1999	782
December 1999	514
April 2000	767
August 2000	417
January 2001	322
May 2001	550
October 2001	86.5
February 2002	182
June 2002	433
November 2002	107
March 2003	230
August 2003	70.7
December 2003	56.7
April 2004	510
September 2004	144
January 2005	201
June 2005	779
October 2005	445
March 2006	694
July 2006	770
November 2006	510
April 2007	703
August 2007	305
January 2008	226
May 2008	565
September 2008	231
February 2009	269
June 2009	471
November 2009	166
March 2010	297
July 2010	377
December 2010	212
April 2011	791
September 2011	637
January 2012	621
May 2012	741
October 2012	278
February 2013	361
July 2013	210
November 2013	45.9
March 2014	188
August 2014	4.56
December 2014	57.9
May 2015	205
September 2015	9.68
January 2016	102
June 2016	518
October 2016	213
March 2017	730
July 2017	784
November 2017	532
April 2018	714
August 2018	389
January 2019	325
May 2019	823
September 2019	596
February 2020	652
June 2020	682
November 2020	378
March 2021	476
July 2021	286
December 2021	136
April 2022	385
September 2022	100
January 2023	133
May 2023	677
October 2023	436
February 2024	598
July 2024	768
November 2024	528
March 2025	796
August 2025	573
December 2025	482
May 2026	524
September 2026	140

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	349	511
Feb	396	534
Mar	480	560
Apr	596	572
May	617	524
Jun	587	433
Jul	500	334
Aug	410	223
Sep	321	140
Oct	280	446
Nov	282	460
Dec	309	482

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

552 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 552 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 552 would be longer than this page and unusable with a screen reader.
Period	Lake Owyhee (m)
1980.75	807
1980.9166666666667	808
1981.1666666666667	810
1981.3333333333333	811
1981.5	808
1981.75	801
1981.9166666666667	803
1982.0833333333333	809
1982.25	813
1982.5	812
1982.6666666666667	809
1982.8333333333333	808
1983.0833333333333	812
1983.25	813
1983.4166666666667	814
1983.6666666666667	809
1983.8333333333333	809
1984	811
1984.1666666666667	812
1984.4166666666667	814
1984.5833333333333	812
1984.75	810
1985	810
1985.1666666666667	811
1985.3333333333333	814
1985.5833333333333	808
1985.75	805
1985.9166666666667	806
1986.1666666666667	813
1986.3333333333333	814
1986.5	811
1986.6666666666667	807
1986.9166666666667	807
1987.0833333333333	808
1987.25	810
1987.5	803
1987.6666666666667	798
1987.8333333333333	796
1988.0833333333333	798
1988.25	801
1988.4166666666667	798
1988.6666666666667	790
1988.8333333333333	790
1989	793
1989.1666666666667	805
1989.4166666666667	812
1989.5833333333333	807
1989.75	804
1990	806
1990.1666666666667	808
1990.3333333333333	808
1990.5833333333333	802
1990.75	797
1990.9166666666667	798
1991.0833333333333	800
1991.3333333333333	802
1991.5	800
1991.6666666666667	793
1991.9166666666667	794
1992.0833333333333	795
1992.25	797
1992.5	790
1992.6666666666667	789
1992.8333333333333	790
1993.0833333333333	793
1993.25	814
1993.4166666666667	813
1993.5833333333333	809
1993.8333333333333	805
1994	806
1994.1666666666667	808
1994.4166666666667	804
1994.5833333333333	797
1994.75	792
1995	795
1995.1666666666667	806
1995.3333333333333	813
1995.5833333333333	810
1995.75	806
1995.9166666666667	807
1996.0833333333333	810
1996.3333333333333	814
1996.5	811
1996.6666666666667	806
1996.9166666666667	806
1997.0833333333333	810
1997.25	814
1997.5	812
1997.6666666666667	807
1997.8333333333333	806
1998	807
1998.25	811
1998.4166666666667	814
1998.5833333333333	811
1998.8333333333333	807
1999	808
1999.1666666666667	810
1999.4166666666667	814
1999.5833333333333	809
1999.75	805
2000	806
2000.1666666666667	809
2000.3333333333333	811
2000.5	806
2000.75	799
2000.9166666666667	800
2001.0833333333333	801
2001.3333333333333	807
2001.5	801
2001.6666666666667	795
2001.9166666666667	794
2002.0833333333333	796
2002.25	805
2002.5	801
2002.6666666666667	795
2002.8333333333333	794
2003	795
2003.25	799
2003.4166666666667	798
2003.5833333333333	792
2003.8333333333333	791
2004	793
2004.1666666666667	799
2004.4166666666667	804
2004.5833333333333	798
2004.75	794
2004.9166666666667	796
2005.1666666666667	799
2005.3333333333333	808
2005.5	810
2005.75	804
2005.9166666666667	805
2006.0833333333333	810
2006.3333333333333	814
2006.5	812
2006.6666666666667	807
2006.9166666666667	806
2007.0833333333333	808
2007.25	810
2007.4166666666667	806
2007.6666666666667	797
2007.8333333333333	796
2008	798
2008.25	805
2008.4166666666667	807
2008.5833333333333	801
2008.8333333333333	797
2009	798
2009.1666666666667	801
2009.4166666666667	805
2009.5833333333333	800
2009.75	795
2009.9166666666667	796
2010.1666666666667	800
2010.3333333333333	804
2010.5	802
2010.75	794
2010.9166666666667	797
2011.0833333333333	805
2011.3333333333333	813
2011.5	813
2011.6666666666667	809
2011.8333333333333	807
2012.0833333333333	809
2012.25	812
2012.4166666666667	809
2012.6666666666667	800
2012.8333333333333	800
2013	801
2013.25	804
2013.4166666666667	800
2013.5833333333333	793
2013.8333333333333	791
2014	793
2014.1666666666667	796
2014.3333333333333	797
2014.5833333333333	790
2014.75	790
2014.9166666666667	792
2015.1666666666667	798
2015.3333333333333	797
2015.5	793
2015.75	790
2015.9166666666667	792
2016.0833333333333	796
2016.3333333333333	807
2016.5	803
2016.6666666666667	798
2016.8333333333333	798
2017.0833333333333	804
2017.25	813
2017.4166666666667	814
2017.6666666666667	807
2017.8333333333333	806
2018	808
2018.25	810
2018.4166666666667	808
2018.5833333333333	803
2018.75	799
2019	801
2019.1666666666667	804
2019.3333333333333	813
2019.5833333333333	810
2019.75	807
2019.9166666666667	807
2020.1666666666667	810
2020.3333333333333	810
2020.5	808
2020.75	802
2020.9166666666667	803
2021.0833333333333	804
2021.25	806
2021.5	800
2021.6666666666667	794
2021.8333333333333	794
2022.0833333333333	797
2022.25	802
2022.4166666666667	802
2022.6666666666667	793
2022.8333333333333	793
2023	795
2023.25	804
2023.4166666666667	810
2023.5833333333333	806
2023.75	804
2024	806
2024.1666666666667	810
2024.3333333333333	814
2024.5833333333333	809
2024.75	806
2024.9166666666667	807
2025.1666666666667	812
2025.3333333333333	814
2025.5	810
2025.6666666666667	805
2025.9166666666667	805
2026.0833333333333	806
2026.25	807
2026.5	801
2026.6666666666667	795

Rate and persistence

-28.81 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

Lake Owyhee

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	1938–2026
Completeness	98.6% 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	99% of the months between 1938 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-7192.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 Owyhee reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usbr-7192/

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 Owyhee 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

1,053 monthly observations 1938–2026 Mm³

Spatially aggregatedHigh confidenceSeptember 2026

Source: USBR — Reservoir operations and Colorado River data, RISE catalogue item 132261. 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.

Period	1991–2020 average (Mm³)	Most recent 12 months (Mm³)
Jan	349	511
Feb	396	534
Mar	480	560
Apr	596	572
May	617	524
Jun	587	433
Jul	500	334
Aug	410	223
Sep	321	140
Oct	280	446
Nov	282	460
Dec	309	482

Period	1991–2020 average (Mm³)	Most recent 12 months (Mm³)
Jan	349	511
Feb	396	534
Mar	480	560
Apr	596	572
May	617	524
Jun	587	433
Jul	500	334
Aug	410	223
Sep	321	140
Oct	280	446
Nov	282	460
Dec	309	482

Period	1991–2020 average (Mm³)	Most recent 12 months (Mm³)
Jan	349	511
Feb	396	534
Mar	480	560
Apr	596	572
May	617	524
Jun	587	433
Jul	500	334
Aug	410	223
Sep	321	140
Oct	280	446
Nov	282	460
Dec	309	482