Lake Owyhee — storage

Storage now, against this reservoir's own record

224.60 Mm³

Stored, August 2026

13th

Percentile among 87 Augs on record

-45.2%

Against the Aug 1991–2020 average

-60.8%

Change over the 12 months to 2026-08

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

Storage, 1938–2026

Monthly mean storage

1,052 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 1,052 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,052 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
November 1954	170
April 1955	328
August 1955	193
January 1956	253
May 1956	844
September 1956	534
February 1957	614
June 1957	869
November 1957	519
March 1958	788
July 1958	793
December 1958	564
April 1959	637
September 1959	213
January 1960	267
May 1960	613
October 1960	201
February 1961	289
July 1961	213
November 1961	59.1
March 1962	234
August 1962	317
December 1962	239
May 1963	446
September 1963	317
January 1964	341
June 1964	803
October 1964	554
March 1965	774
July 1965	804
November 1965	643
April 1966	799
August 1966	428
January 1967	373
May 1967	577
September 1967	440
February 1968	486
June 1968	412
November 1968	174
March 1969	488
July 1969	763
December 1969	565
April 1970	865
September 1970	618
January 1971	793
May 1971	878
October 1971	578
February 1972	724
July 1972	776
November 1972	569
March 1973	804
August 1973	592
December 1973	522
May 1974	874
September 1974	506
January 1975	519
June 1975	877
October 1975	616
March 1976	817
July 1976	716
November 1976	547
April 1977	630
August 1977	305
January 1978	295
May 1978	885
September 1978	568
February 1979	683
June 1979	844
November 1979	531
March 1980	828
July 1980	807
December 1980	604
April 1981	765
September 1981	373
January 1982	494
May 1982	880
October 1982	599
February 1983	798
June 1983	881
November 1983	650
March 1984	790
August 1984	786
December 1984	735
April 1985	865
September 1985	511
January 1986	547
June 1986	854
October 1986	539
February 1987	623
July 1987	425
November 1987	172
April 1988	351
August 1988	70.4
December 1988	57.2
May 1989	865
September 1989	494
February 1990	531
June 1990	567
October 1990	215
March 1991	337
July 1991	286
December 1991	103
April 1992	204
November 1992	13.2
April 1993	882
August 1993	654
January 1994	534
May 1994	518
September 1994	104
February 1995	342
June 1995	871
November 1995	540
March 1996	772
July 1996	746
December 1996	511
April 1997	878
September 1997	567
January 1998	557
May 1998	863
October 1998	557
February 1999	654
July 1999	782
November 1999	491
March 2000	662
August 2000	417
December 2000	299
May 2001	550
September 2001	143
January 2002	150
June 2002	433
October 2002	93.5
March 2003	230
July 2003	158
November 2003	34.4
April 2004	510
August 2004	226
January 2005	201
May 2005	607
September 2005	491
February 2006	703
June 2006	862
November 2006	510
March 2007	687
July 2007	425
December 2007	204
April 2008	479
September 2008	231
January 2009	241
May 2009	509
October 2009	149
February 2010	246
July 2010	377
November 2010	143
March 2011	621
August 2011	745
December 2011	597
April 2012	788
September 2012	317
January 2013	335
June 2013	311
October 2013	27.0
February 2014	125
July 2014	41.5
November 2014	27.6
April 2015	247
August 2015	27.6
December 2015	69.1
May 2016	559
September 2016	233
February 2017	458
June 2017	870
October 2017	518
March 2018	661
July 2018	501
December 2018	303
April 2019	679
August 2019	697
January 2020	607
May 2020	717
October 2020	364
February 2021	440
June 2021	392
November 2021	115
March 2022	260
August 2022	189
December 2022	103
April 2023	433
September 2023	470
January 2024	503
June 2024	860
October 2024	517
February 2025	676
July 2025	686
November 2025	460
April 2026	572
August 2026	225

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	225
Sep	321	486
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

551 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 551 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 551 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
1986.0833333333333	810
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	798
1988.25	801
1988.4166666666667	798
1988.5833333333333	792
1988.8333333333333	790
1989	793
1989.1666666666667	805
1989.4166666666667	812
1989.5833333333333	807
1989.75	804
1989.9166666666667	805
1990.1666666666667	808
1990.3333333333333	808
1990.5	805
1990.75	797
1990.9166666666667	798
1991.0833333333333	800
1991.3333333333333	802
1991.5	800
1991.6666666666667	793
1991.8333333333333	793
1992.0833333333333	795
1992.25	797
1992.4166666666667	792
1992.6666666666667	789
1992.8333333333333	790
1993	792
1993.25	814
1993.4166666666667	813
1993.5833333333333	809
1993.75	805
1994	806
1994.1666666666667	808
1994.3333333333333	806
1994.5833333333333	797
1994.75	792
1994.9166666666667	793
1995.1666666666667	806
1995.3333333333333	813
1995.5	812
1995.6666666666667	808
1995.9166666666667	807
1996.0833333333333	810
1996.25	813
1996.5	811
1996.6666666666667	806
1996.8333333333333	805
1997.0833333333333	810
1997.25	814
1997.4166666666667	813
1997.6666666666667	807
1997.8333333333333	806
1998	807
1998.1666666666667	809
1998.4166666666667	814
1998.5833333333333	811
1998.75	807
1999	808
1999.1666666666667	810
1999.3333333333333	814
1999.5833333333333	809
1999.75	805
1999.9166666666667	806
2000.0833333333333	807
2000.3333333333333	811
2000.5	806
2000.6666666666667	801
2000.9166666666667	800
2001.0833333333333	801
2001.25	807
2001.5	801
2001.6666666666667	795
2001.8333333333333	793
2002	795
2002.25	805
2002.4166666666667	804
2002.5833333333333	798
2002.8333333333333	794
2003	795
2003.1666666666667	798
2003.4166666666667	798
2003.5833333333333	792
2003.75	790
2003.9166666666667	792
2004.1666666666667	799
2004.3333333333333	805
2004.5	801
2004.75	794
2004.9166666666667	796
2005.0833333333333	798
2005.3333333333333	808
2005.5	810
2005.6666666666667	805
2005.8333333333333	804
2006.0833333333333	810
2006.25	812
2006.4166666666667	813
2006.6666666666667	807
2006.8333333333333	806
2007	807
2007.25	810
2007.4166666666667	806
2007.5833333333333	800
2007.75	796
2008	798
2008.1666666666667	800
2008.3333333333333	807
2008.5833333333333	801
2008.75	796
2008.9166666666667	797
2009.1666666666667	801
2009.3333333333333	806
2009.5	803
2009.6666666666667	797
2009.9166666666667	796
2010.0833333333333	798
2010.25	803
2010.5	802
2010.6666666666667	796
2010.8333333333333	795
2011.0833333333333	805
2011.25	812
2011.4166666666667	814
2011.6666666666667	809
2011.8333333333333	807
2012	808
2012.1666666666667	810
2012.4166666666667	809
2012.5833333333333	803
2012.75	799
2013	801
2013.1666666666667	803
2013.3333333333333	803
2013.5833333333333	793
2013.75	791
2013.9166666666667	792
2014.0833333333333	794
2014.3333333333333	797
2014.5	791
2014.6666666666667	790
2014.9166666666667	792
2015.0833333333333	796
2015.25	798
2015.5	793
2015.6666666666667	790
2015.8333333333333	791
2016	794
2016.25	806
2016.4166666666667	806
2016.5833333333333	801
2016.8333333333333	798
2017	799
2017.1666666666667	811
2017.4166666666667	814
2017.5833333333333	809
2017.75	806
2017.9166666666667	807
2018.1666666666667	809
2018.3333333333333	810
2018.5	805
2018.75	799
2018.9166666666667	800
2019.0833333333333	802
2019.3333333333333	813
2019.5	812
2019.6666666666667	808
2019.8333333333333	807
2020.0833333333333	809
2020.25	811
2020.4166666666667	810
2020.6666666666667	803
2020.8333333333333	802
2021	803
2021.25	806
2021.4166666666667	803
2021.5833333333333	796
2021.75	793
2022	796
2022.1666666666667	799
2022.3333333333333	803
2022.5833333333333	797
2022.75	792
2022.9166666666667	794
2023.1666666666667	797
2023.3333333333333	810
2023.5	809
2023.6666666666667	805
2023.9166666666667	805
2024.0833333333333	808
2024.25	813
2024.5	812
2024.6666666666667	807
2024.8333333333333	806
2025.0833333333333	810
2025.25	814
2025.4166666666667	812
2025.5833333333333	807
2025.8333333333333	804
2026	806
2026.1666666666667	807
2026.4166666666667	804
2026.5833333333333	798

Rate and persistence

-29.02 Mm³

Mean drawdown per month over 12 months

3 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	98.5% 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	99% of the months between 1938 and 2026 are held. Monthly means of the publisher's own daily record.
Last read from the publisher	2026-09-01
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-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 2026-09-02, 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

1,052 monthly observations 1938–2026 Mm³

Spatially aggregatedHigh confidenceAugust 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 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.

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	225
Sep	321	486
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	225
Sep	321	486
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	225
Sep	321	486
Oct	280	446
Nov	282	460
Dec	309	482