Shadehill Reservoir — storage

Storage now, against this reservoir's own record

113.20 Mm³

Stored, September 2026

18th

Percentile among 75 Seps on record

-11.0%

Against the Sep 1991–2020 average

-9.7%

Change over the 12 months to 2026-09

Storage in September 2026 was lower than most Seps on record, ranked against 75 other Seps held for this reservoir.

Storage, 1951–2026

Monthly mean storage

900 monthly values, 1951 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 900 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 900 would be longer than this page and unusable with a screen reader.
Period	Shadehill Reservoir (Mm³)
October 1951	0
February 1952	0
June 1952	174
September 1952	170
January 1953	166
May 1953	175
September 1953	172
December 1953	171
April 1954	175
August 1954	170
December 1954	165
March 1955	166
July 1955	171
November 1955	162
March 1956	165
June 1956	173
October 1956	168
February 1957	165
June 1957	173
September 1957	173
January 1958	170
May 1958	172
September 1958	166
January 1959	160
April 1959	175
August 1959	167
December 1959	159
April 1960	173
July 1960	173
November 1960	145
March 1961	134
July 1961	126
October 1961	115
February 1962	106
June 1962	137
October 1962	139
January 1963	126
May 1963	145
September 1963	144
January 1964	113
April 1964	106
August 1964	146
December 1964	130
April 1965	156
August 1965	168
November 1965	135
March 1966	142
July 1966	170
November 1966	154
February 1967	141
June 1967	179
October 1967	138
February 1968	119
May 1968	121
September 1968	119
January 1969	116
May 1969	165
August 1969	169
December 1969	145
April 1970	134
August 1970	164
November 1970	146
March 1971	171
July 1971	172
November 1971	152
February 1972	133
June 1972	175
October 1972	155
February 1973	155
June 1973	174
September 1973	155
January 1974	138
May 1974	140
September 1974	124
December 1974	119
April 1975	126
August 1975	161
December 1975	144
March 1976	151
July 1976	168
November 1976	150
March 1977	149
June 1977	154
October 1977	155
February 1978	146
June 1978	173
September 1978	159
January 1979	141
May 1979	171
September 1979	158
January 1980	131
April 1980	130
August 1980	117
December 1980	112
April 1981	112
July 1981	108
November 1981	103
March 1982	139
July 1982	167
October 1982	156
February 1983	152
June 1983	170
October 1983	145
January 1984	143
May 1984	162
September 1984	145
January 1985	135
April 1985	169
August 1985	159
December 1985	151
April 1986	175
August 1986	164
November 1986	152
March 1987	159
July 1987	169
November 1987	146
February 1988	138
June 1988	142
October 1988	129
February 1989	123
May 1989	147
September 1989	142
January 1990	140
May 1990	157
August 1990	148
December 1990	137
April 1991	137
August 1991	140
November 1991	131
March 1992	130
July 1992	135
November 1992	130
March 1993	149
June 1993	173
October 1993	163
February 1994	152
June 1994	174
September 1994	165
January 1995	154
May 1995	183
September 1995	161
December 1995	126
April 1996	151
August 1996	145
December 1996	128
March 1997	153
July 1997	146
November 1997	123
March 1998	125
June 1998	142
October 1998	126
February 1999	132
June 1999	150
October 1999	130
January 2000	122
May 2000	124
September 2000	110
January 2001	104
April 2001	155
August 2001	147
December 2001	121
April 2002	116
July 2002	109
November 2002	97.1
March 2003	96.2
July 2003	102
October 2003	94.8
February 2004	91.6
June 2004	133
October 2004	120
January 2005	115
May 2005	111
September 2005	102
January 2006	95.9
May 2006	113
August 2006	104
December 2006	93.7
April 2007	92.6
August 2007	90.1
November 2007	82.0
March 2008	76.4
July 2008	101
November 2008	98.0
February 2009	101
June 2009	144
October 2009	127
February 2010	115
May 2010	152
September 2010	134
January 2011	115
May 2011	153
August 2011	150
December 2011	101
April 2012	104
August 2012	104
November 2012	97.7
March 2013	98.4
July 2013	122
November 2013	146
March 2014	154
June 2014	152
October 2014	145
February 2015	127
June 2015	136
September 2015	142
January 2016	118
May 2016	118
September 2016	105
December 2016	101
April 2017	113
August 2017	107
December 2017	101
March 2018	99.5
July 2018	147
November 2018	136
March 2019	161
June 2019	153
October 2019	140
February 2020	125
June 2020	143
October 2020	130
January 2021	120
May 2021	107
September 2021	93.3
January 2022	90.6
April 2022	91.0
August 2022	119
December 2022	109
April 2023	122
July 2023	147
November 2023	136
March 2024	126
July 2024	119
October 2024	99.1
February 2025	97.6
June 2025	129
October 2025	124
January 2026	126
May 2026	127
September 2026	113

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	116	126
Feb	116	127
Mar	128	128
Apr	137	128
May	136	127
Jun	136	125
Jul	135	121
Aug	131	117
Sep	127	113
Oct	124	124
Nov	120	124
Dec	117	124

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

900 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 900 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 900 would be longer than this page and unusable with a screen reader.
Period	Shadehill Reservoir (m)
1951.75	0
1952.0833333333333	0
1952.4166666666667	693
1952.6666666666667	692
1953	692
1953.3333333333333	693
1953.6666666666667	692
1953.9166666666667	692
1954.25	693
1954.5833333333333	692
1954.9166666666667	692
1955.1666666666667	692
1955.5	692
1955.8333333333333	692
1956.1666666666667	692
1956.4166666666667	693
1956.75	692
1957.0833333333333	692
1957.4166666666667	693
1957.6666666666667	693
1958	692
1958.3333333333333	693
1958.6666666666667	692
1959	692
1959.25	693
1959.5833333333333	692
1959.9166666666667	692
1960.25	693
1960.5	693
1960.8333333333333	691
1961.1666666666667	690
1961.5	690
1961.75	689
1962.0833333333333	689
1962.4166666666667	691
1962.75	691
1963	690
1963.3333333333333	691
1963.6666666666667	691
1964	689
1964.25	689
1964.5833333333333	691
1964.9166666666667	690
1965.25	692
1965.5833333333333	692
1965.8333333333333	690
1966.1666666666667	691
1966.5	692
1966.8333333333333	692
1967.0833333333333	691
1967.4166666666667	693
1967.75	691
1968.0833333333333	689
1968.3333333333333	690
1968.6666666666667	689
1969	689
1969.3333333333333	692
1969.5833333333333	692
1969.9166666666667	691
1970.25	690
1970.5833333333333	692
1970.8333333333333	691
1971.1666666666667	692
1971.5	693
1971.8333333333333	691
1972.0833333333333	690
1972.4166666666667	693
1972.75	692
1973.0833333333333	692
1973.4166666666667	693
1973.6666666666667	692
1974	691
1974.3333333333333	691
1974.6666666666667	690
1974.9166666666667	690
1975.25	690
1975.5833333333333	692
1975.9166666666667	691
1976.1666666666667	691
1976.5	692
1976.8333333333333	691
1977.1666666666667	691
1977.4166666666667	692
1977.75	692
1978.0833333333333	691
1978.4166666666667	693
1978.6666666666667	692
1979	691
1979.3333333333333	692
1979.6666666666667	692
1980	690
1980.25	690
1980.5833333333333	689
1980.9166666666667	689
1981.25	689
1981.5	689
1981.8333333333333	688
1982.1666666666667	691
1982.5	692
1982.75	692
1983.0833333333333	691
1983.4166666666667	692
1983.75	691
1984	691
1984.3333333333333	692
1984.6666666666667	691
1985	691
1985.25	692
1985.5833333333333	692
1985.9166666666667	691
1986.25	693
1986.5833333333333	692
1986.8333333333333	691
1987.1666666666667	692
1987.5	692
1987.8333333333333	691
1988.0833333333333	691
1988.4166666666667	691
1988.75	690
1989.0833333333333	690
1989.3333333333333	691
1989.6666666666667	691
1990	691
1990.3333333333333	692
1990.5833333333333	691
1990.9166666666667	691
1991.25	691
1991.5833333333333	691
1991.8333333333333	690
1992.1666666666667	690
1992.5	690
1992.8333333333333	690
1993.1666666666667	691
1993.4166666666667	693
1993.75	692
1994.0833333333333	691
1994.4166666666667	693
1994.6666666666667	692
1995	692
1995.3333333333333	693
1995.6666666666667	692
1995.9166666666667	691
1996.25	693
1996.5833333333333	692
1996.9166666666667	691
1997.1666666666667	693
1997.5	692
1997.8333333333333	691
1998.1666666666667	691
1998.4166666666667	692
1998.75	691
1999.0833333333333	692
1999.4166666666667	693
1999.75	692
2000	691
2000.3333333333333	691
2000.6666666666667	690
2001	690
2001.25	693
2001.5833333333333	692
2001.9166666666667	691
2002.25	691
2002.5	690
2002.8333333333333	690
2003.1666666666667	690
2003.5	690
2003.75	689
2004.0833333333333	689
2004.4166666666667	692
2004.75	691
2005	691
2005.3333333333333	691
2005.6666666666667	690
2006	690
2006.3333333333333	691
2006.5833333333333	690
2006.9166666666667	689
2007.25	689
2007.5833333333333	689
2007.8333333333333	689
2008.1666666666667	688
2008.5	690
2008.8333333333333	690
2009.0833333333333	690
2009.4166666666667	692
2009.75	691
2010.0833333333333	691
2010.3333333333333	693
2010.6666666666667	692
2011	691
2011.3333333333333	693
2011.5833333333333	693
2011.9166666666667	690
2012.25	690
2012.5833333333333	690
2012.8333333333333	690
2013.1666666666667	690
2013.5	691
2013.8333333333333	692
2014.1666666666667	693
2014.4166666666667	693
2014.75	692
2015.0833333333333	691
2015.4166666666667	692
2015.6666666666667	692
2016	691
2016.3333333333333	691
2016.6666666666667	690
2016.9166666666667	690
2017.25	691
2017.5833333333333	690
2017.9166666666667	690
2018.1666666666667	690
2018.5	692
2018.8333333333333	692
2019.1666666666667	693
2019.4166666666667	693
2019.75	692
2020.0833333333333	691
2020.4166666666667	692
2020.75	692
2021	691
2021.3333333333333	690
2021.6666666666667	689
2022	689
2022.25	689
2022.5833333333333	691
2022.9166666666667	690
2023.25	691
2023.5	692
2023.8333333333333	692
2024.1666666666667	691
2024.5	691
2024.75	690
2025.0833333333333	690
2025.4166666666667	692
2025.75	691
2026	691
2026.3333333333333	691
2026.6666666666667	691

Rate and persistence

-1.01 Mm³

Mean drawdown per month over 12 months

11 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

Shadehill 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	1951–2026
Completeness	98.7% 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	99% of the months between 1951 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-476.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), Shadehill Reservoir reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usbr-476/

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 Shadehill 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

900 monthly observations 1951–2026 Mm³

Spatially aggregatedHigh confidenceSeptember 2026

Source: USBR — Reservoir operations and Colorado River data, RISE catalogue item 748. 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	116	126
Feb	116	127
Mar	128	128
Apr	137	128
May	136	127
Jun	136	125
Jul	135	121
Aug	131	117
Sep	127	113
Oct	124	124
Nov	120	124
Dec	117	124

Period	1991–2020 average (Mm³)	Most recent 12 months (Mm³)
Jan	116	126
Feb	116	127
Mar	128	128
Apr	137	128
May	136	127
Jun	136	125
Jul	135	121
Aug	131	117
Sep	127	113
Oct	124	124
Nov	120	124
Dec	117	124

Period	1991–2020 average (Mm³)	Most recent 12 months (Mm³)
Jan	116	126
Feb	116	127
Mar	128	128
Apr	137	128
May	136	127
Jun	136	125
Jul	135	121
Aug	131	117
Sep	127	113
Oct	124	124
Nov	120	124
Dec	117	124