Deadwood Reservoir — storage

Storage now, against this reservoir's own record

87.13 Mm³

Stored, September 2026

40th

Percentile among 96 Seps on record

-15.3%

Against the Sep 1991–2020 average

-0.9%

Change over the 12 months to 2026-09

Storage in September 2026 was around the middle of the Sep record, ranked against 96 other Seps held for this reservoir.

Storage, 1931–2026

Monthly mean storage

1,149 monthly values, 1931 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 1,149 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,149 would be longer than this page and unusable with a screen reader.
Period	Deadwood Reservoir (Mm³)
January 1931	3.47
June 1931	63.3
November 1931	4.92
March 1932	21.5
August 1932	170
January 1933	56.1
June 1933	169
November 1933	55.1
March 1934	78.7
August 1934	102
January 1935	21.8
June 1935	136
November 1935	23.5
March 1936	33.9
August 1936	162
January 1937	60.5
June 1937	145
November 1937	50.8
March 1938	73.5
August 1938	195
January 1939	107
June 1939	201
November 1939	69.0
March 1940	89.8
August 1940	159
January 1941	113
June 1941	205
November 1941	149
March 1942	184
August 1942	184
January 1943	122
June 1943	208
November 1943	108
April 1944	137
August 1944	159
January 1945	73.0
June 1945	187
November 1945	103
April 1946	143
August 1946	178
January 1947	128
June 1947	206
November 1947	75.4
April 1948	110
August 1948	199
January 1949	100
June 1949	190
November 1949	108
April 1950	138
August 1950	201
January 1951	120
June 1951	198
November 1951	10.7
April 1952	46.5
August 1952	194
January 1953	69.8
June 1953	192
November 1953	82.3
April 1954	117
August 1954	173
January 1955	76.8
June 1955	168
November 1955	61.5
April 1956	103
August 1956	185
January 1957	75.0
June 1957	204
November 1957	39.4
April 1958	66.8
August 1958	172
January 1959	71.4
June 1959	191
November 1959	75.6
April 1960	114
August 1960	162
January 1961	54.7
June 1961	160
November 1961	53.8
April 1962	86.2
August 1962	184
January 1963	101
June 1963	207
November 1963	88.7
April 1964	120
August 1964	128
January 1965	109
June 1965	198
November 1965	111
April 1966	146
August 1966	138
January 1967	65.8
June 1967	183
November 1967	84.3
April 1968	119
September 1968	59.2
January 1969	88.8
June 1969	199
November 1969	82.2
April 1970	114
September 1970	89.2
January 1971	110
June 1971	186
November 1971	82.7
April 1972	118
September 1972	109
January 1973	108
June 1973	174
November 1973	12.6
April 1974	73.3
September 1974	112
January 1975	99.0
June 1975	148
November 1975	91.8
April 1976	134
September 1976	87.4
January 1977	99.5
June 1977	105
November 1977	42.2
April 1978	84.9
September 1978	102
January 1979	95.2
June 1979	184
November 1979	55.0
April 1980	85.7
September 1980	102
January 1981	130
June 1981	206
November 1981	85.4
April 1982	130
September 1982	88.1
January 1983	118
June 1983	208
November 1983	101
April 1984	145
September 1984	110
January 1985	130
June 1985	200
November 1985	88.1
April 1986	151
September 1986	81.3
January 1987	106
June 1987	164
November 1987	68.2
April 1988	97.6
September 1988	53.4
January 1989	70.1
June 1989	192
November 1989	95.2
April 1990	131
September 1990	83.6
February 1991	104
June 1991	171
November 1991	72.8
April 1992	85.5
September 1992	57.1
February 1993	67.5
June 1993	202
November 1993	123
April 1994	132
September 1994	64.6
February 1995	70.1
June 1995	202
November 1995	159
April 1996	150
September 1996	154
February 1997	137
June 1997	202
November 1997	154
April 1998	156
September 1998	146
February 1999	153
June 1999	188
November 1999	138
April 2000	156
September 2000	114
February 2001	115
June 2001	146
November 2001	63.8
April 2002	74.8
September 2002	66.9
February 2003	73.9
June 2003	191
November 2003	98.1
April 2004	119
September 2004	85.2
February 2005	91.6
June 2005	178
November 2005	83.5
April 2006	105
September 2006	112
February 2007	126
June 2007	201
November 2007	71.4
April 2008	85.8
September 2008	91.2
February 2009	101
June 2009	189
November 2009	112
April 2010	122
September 2010	112
February 2011	125
June 2011	177
November 2011	113
April 2012	140
September 2012	103
February 2013	121
June 2013	185
November 2013	86.3
April 2014	128
September 2014	115
February 2015	147
July 2015	160
November 2015	84.9
April 2016	116
September 2016	105
February 2017	121
July 2017	187
November 2017	149
April 2018	146
September 2018	101
February 2019	108
July 2019	181
November 2019	108
April 2020	118
September 2020	93.4
February 2021	99.6
July 2021	133
November 2021	73.1
April 2022	89.8
September 2022	88.0
February 2023	96.4
July 2023	180
November 2023	116
April 2024	137
September 2024	76.7
February 2025	100
July 2025	174
November 2025	99.5
April 2026	170
September 2026	87.1

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	110	123
Feb	111	131
Mar	112	141
Apr	119	170
May	152	184
Jun	186	187
Jul	174	177
Aug	131	119
Sep	103	87.1
Oct	104	92.7
Nov	106	99.5
Dec	109	109

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

753 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 753 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 753 would be longer than this page and unusable with a screen reader.
Period	Deadwood Reservoir (m)
1960.9166666666667	1,610
1961.1666666666667	1,613
1961.4166666666667	1,622
1961.6666666666667	1,609
1962	1,612
1962.25	1,615
1962.5	1,625
1962.75	1,613
1963	1,617
1963.25	1,621
1963.5	1,625
1963.8333333333333	1,616
1964.0833333333333	1,618
1964.3333333333333	1,621
1964.5833333333333	1,620
1964.8333333333333	1,615
1965.0833333333333	1,619
1965.3333333333333	1,619
1965.6666666666667	1,617
1965.9166666666667	1,618
1966.1666666666667	1,620
1966.4166666666667	1,626
1966.6666666666667	1,616
1966.9166666666667	1,612
1967.25	1,615
1967.5	1,626
1967.75	1,614
1968	1,616
1968.25	1,619
1968.5	1,623
1968.75	1,613
1969.0833333333333	1,616
1969.3333333333333	1,621
1969.5833333333333	1,618
1969.8333333333333	1,615
1970.0833333333333	1,617
1970.3333333333333	1,621
1970.5833333333333	1,622
1970.9166666666667	1,617
1971.1666666666667	1,619
1971.4166666666667	1,625
1971.6666666666667	1,618
1971.9166666666667	1,616
1972.1666666666667	1,618
1972.4166666666667	1,624
1972.75	1,616
1973	1,618
1973.25	1,619
1973.5	1,619
1973.75	1,595
1974	1,607
1974.25	1,614
1974.5833333333333	1,623
1974.8333333333333	1,615
1975.0833333333333	1,617
1975.3333333333333	1,618
1975.5833333333333	1,623
1975.8333333333333	1,616
1976.0833333333333	1,618
1976.4166666666667	1,626
1976.6666666666667	1,615
1976.9166666666667	1,616
1977.1666666666667	1,617
1977.4166666666667	1,617
1977.6666666666667	1,608
1981	1,620
1981.25	1,622
1981.5	1,624
1981.75	1,615
1982	1,617
1982.25	1,620
1982.5	1,626
1982.8333333333333	1,617
1983.0833333333333	1,619
1983.3333333333333	1,624
1983.5833333333333	1,623
1983.8333333333333	1,617
1984.0833333333333	1,619
1984.3333333333333	1,624
1984.6666666666667	1,618
1984.9166666666667	1,619
1985.1666666666667	1,621
1985.4166666666667	1,626
1985.6666666666667	1,614
1985.9166666666667	1,616
1986.1666666666667	1,619
1986.5	1,622
1986.75	1,616
1987	1,617
1987.25	1,620
1987.5	1,616
1987.75	1,613
1988	1,614
1988.3333333333333	1,620
1988.5833333333333	1,612
1988.8333333333333	1,612
1989.0833333333333	1,614
1989.3333333333333	1,621
1989.5833333333333	1,618
1989.8333333333333	1,616
1990.1666666666667	1,618
1990.4166666666667	1,626
1990.6666666666667	1,615
1990.9166666666667	1,616
1991.1666666666667	1,618
1991.4166666666667	1,623
1991.75	1,614
1992	1,614
1992.25	1,615
1992.5	1,616
1992.75	1,610
1993	1,612
1993.25	1,615
1993.5833333333333	1,622
1993.8333333333333	1,619
1994.0833333333333	1,619
1994.3333333333333	1,622
1994.5833333333333	1,614
1994.8333333333333	1,612
1995.0833333333333	1,613
1995.4166666666667	1,626
1995.6666666666667	1,622
1995.9166666666667	1,623
1996.1666666666667	1,622
1996.4166666666667	1,627
1996.6666666666667	1,622
1996.9166666666667	1,623
1997.25	1,614
1997.5	1,626
1997.75	1,622
1998	1,622
1998.25	1,622
1998.5	1,626
1998.75	1,621
1999.0833333333333	1,622
1999.3333333333333	1,618
1999.5833333333333	1,623
1999.8333333333333	1,621
2000.0833333333333	1,621
2000.3333333333333	1,625
2000.6666666666667	1,618
2000.9166666666667	1,618
2001.1666666666667	1,618
2001.4166666666667	1,621
2001.6666666666667	1,612
2001.9166666666667	1,613
2002.1666666666667	1,613
2002.5	1,622
2002.75	1,613
2003	1,613
2003.25	1,615
2003.5	1,625
2003.75	1,617
2004	1,617
2004.3333333333333	1,622
2004.5833333333333	1,619
2004.8333333333333	1,615
2005.0833333333333	1,616
2005.3333333333333	1,620
2005.5833333333333	1,619
2005.8333333333333	1,615
2006.1666666666667	1,616
2006.4166666666667	1,626
2006.6666666666667	1,618
2006.9166666666667	1,619
2007.1666666666667	1,620
2007.4166666666667	1,626
2007.6666666666667	1,613
2008	1,615
2008.25	1,616
2008.5	1,625
2008.75	1,617
2009	1,617
2009.25	1,618
2009.5	1,625
2009.8333333333333	1,619
2010.0833333333333	1,619
2010.3333333333333	1,622
2010.5833333333333	1,620
2010.8333333333333	1,619
2011.0833333333333	1,620
2011.4166666666667	1,625
2011.6666666666667	1,618
2011.9166666666667	1,619
2012.1666666666667	1,620
2012.4166666666667	1,625
2012.6666666666667	1,618
2012.9166666666667	1,619
2013.25	1,621
2013.5	1,623
2013.75	1,615
2014	1,617
2014.25	1,620
2014.5	1,625
2014.75	1,619
2015.0833333333333	1,622
2015.3333333333333	1,626
2015.5833333333333	1,619
2015.8333333333333	1,616
2016.0833333333333	1,616
2016.3333333333333	1,624
2016.5833333333333	1,620
2016.9166666666667	1,619
2017.1666666666667	1,621
2017.4166666666667	1,625
2017.6666666666667	1,621
2018	1,622
2018.25	1,622
2018.5	1,625
2018.8333333333333	1,618
2019.0833333333333	1,618
2019.3333333333333	1,623
2019.5833333333333	1,621
2019.8333333333333	1,618
2020.0833333333333	1,619
2020.3333333333333	1,623
2020.6666666666667	1,617
2020.9166666666667	1,617
2021.1666666666667	1,618
2021.4166666666667	1,624
2021.6666666666667	1,614
2021.9166666666667	1,615
2022.25	1,616
2022.5	1,625
2022.75	1,616
2023	1,617
2023.25	1,618
2023.5	1,625
2023.75	1,619
2024.0833333333333	1,620
2024.3333333333333	1,624
2024.5833333333333	1,618
2024.8333333333333	1,616
2025.0833333333333	1,618
2025.3333333333333	1,623
2025.5833333333333	1,620
2025.9166666666667	1,619
2026.1666666666667	1,622
2026.4166666666667	1,626
2026.6666666666667	1,616

Rate and persistence

-0.07 Mm³

Mean drawdown per month over 12 months

0 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

Deadwood 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	1931–2026
Completeness	99.7% 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	100% of the months between 1931 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-3649.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), Deadwood Reservoir reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usbr-3649/

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 Deadwood 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

1,149 monthly observations 1931–2026 Mm³

Spatially aggregatedHigh confidenceSeptember 2026

Source: USBR — Reservoir operations and Colorado River data, RISE catalogue item 130055. 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.