Shadehill Reservoir — storage

Storage now, against this reservoir's own record

116.79 Mm³

Stored, August 2026

18th

Percentile among 75 Augs on record

-10.9%

Against the Aug 1991–2020 average

-8.1%

Change over the 12 months to 2026-08

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

Storage, 1951–2026

Monthly mean storage

899 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 899 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 899 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
December 1958	161
April 1959	175
August 1959	167
December 1959	159
March 1960	161
July 1960	173
November 1960	145
March 1961	134
June 1961	131
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
July 1965	175
November 1965	135
March 1966	142
July 1966	170
October 1966	160
February 1967	141
June 1967	179
October 1967	138
January 1968	123
May 1968	121
September 1968	119
January 1969	116
April 1969	177
August 1969	169
December 1969	145
April 1970	134
July 1970	170
November 1970	146
March 1971	171
July 1971	172
October 1971	156
February 1972	133
June 1972	175
October 1972	155
January 1973	144
May 1973	173
September 1973	155
January 1974	138
May 1974	140
August 1974	128
December 1974	119
April 1975	126
August 1975	161
November 1975	145
March 1976	151
July 1976	168
November 1976	150
February 1977	147
June 1977	154
October 1977	155
February 1978	146
May 1978	176
September 1978	159
January 1979	141
May 1979	171
August 1979	163
December 1979	132
April 1980	130
August 1980	117
November 1980	113
March 1981	113
July 1981	108
November 1981	103
February 1982	116
June 1982	177
October 1982	156
February 1983	152
May 1983	168
September 1983	153
January 1984	143
May 1984	162
September 1984	145
December 1984	137
April 1985	169
August 1985	159
December 1985	151
March 1986	174
July 1986	168
November 1986	152
March 1987	159
June 1987	173
October 1987	151
February 1988	138
June 1988	142
September 1988	131
January 1989	124
May 1989	147
September 1989	142
December 1989	139
April 1990	157
August 1990	148
December 1990	137
March 1991	135
July 1991	144
November 1991	131
March 1992	130
June 1992	130
October 1992	131
February 1993	129
June 1993	173
September 1993	167
January 1994	155
May 1994	176
September 1994	165
January 1995	154
April 1995	169
August 1995	166
December 1995	126
April 1996	151
July 1996	149
November 1996	131
March 1997	153
July 1997	146
October 1997	126
February 1998	122
June 1998	142
October 1998	126
January 1999	124
May 1999	151
September 1999	137
January 2000	122
April 2000	123
August 2000	116
December 2000	106
April 2001	155
July 2001	153
November 2001	123
March 2002	115
July 2002	109
October 2002	98.8
February 2003	91.8
June 2003	104
October 2003	94.8
January 2004	90.9
May 2004	135
September 2004	124
January 2005	115
May 2005	111
August 2005	106
December 2005	96.4
April 2006	103
August 2006	104
November 2006	96.1
March 2007	89.8
July 2007	93.8
November 2007	82.0
February 2008	76.7
June 2008	99.3
October 2008	97.3
February 2009	101
May 2009	156
September 2009	131
January 2010	118
May 2010	152
August 2010	141
December 2010	119
April 2011	154
August 2011	150
November 2011	114
March 2012	102
July 2012	107
November 2012	97.7
February 2013	97.4
June 2013	117
October 2013	150
February 2014	133
May 2014	149
September 2014	150
January 2015	125
May 2015	128
August 2015	145
December 2015	121
April 2016	117
August 2016	107
December 2016	101
March 2017	105
July 2017	109
November 2017	103
March 2018	99.5
June 2018	148
October 2018	136
February 2019	138
June 2019	153
September 2019	142
January 2020	126
May 2020	146
September 2020	134
December 2020	124
April 2021	110
August 2021	97.5
December 2021	91.6
March 2022	88.4
July 2022	121
November 2022	110
March 2023	109
June 2023	143
October 2023	141
February 2024	128
June 2024	121
September 2024	102
January 2025	97.8
May 2025	116
September 2025	125
December 2025	124
April 2026	128
August 2026	117

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	125
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

899 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 899 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 899 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
1958.9166666666667	692
1959.25	693
1959.5833333333333	692
1959.9166666666667	692
1960.1666666666667	692
1960.5	693
1960.8333333333333	691
1961.1666666666667	690
1961.4166666666667	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
1965.5	693
1965.8333333333333	690
1966.1666666666667	691
1966.5	692
1966.75	692
1967.0833333333333	691
1967.4166666666667	693
1967.75	691
1968	690
1968.3333333333333	690
1968.6666666666667	689
1969	689
1969.25	693
1969.5833333333333	692
1969.9166666666667	691
1970.25	690
1970.5	692
1970.8333333333333	691
1971.1666666666667	692
1971.5	693
1971.75	692
1972.0833333333333	690
1972.4166666666667	693
1972.75	692
1973	691
1973.3333333333333	693
1973.6666666666667	692
1974	691
1974.3333333333333	691
1974.5833333333333	690
1974.9166666666667	690
1975.25	690
1975.5833333333333	692
1975.8333333333333	691
1976.1666666666667	691
1976.5	692
1976.8333333333333	691
1977.0833333333333	691
1977.4166666666667	692
1977.75	692
1978.0833333333333	691
1978.3333333333333	693
1978.6666666666667	692
1979	691
1979.3333333333333	692
1979.5833333333333	692
1979.9166666666667	690
1980.25	690
1980.5833333333333	689
1980.8333333333333	689
1981.1666666666667	689
1981.5	689
1981.8333333333333	688
1982.0833333333333	689
1982.4166666666667	693
1982.75	692
1983.0833333333333	691
1983.3333333333333	692
1983.6666666666667	692
1984	691
1984.3333333333333	692
1984.6666666666667	691
1984.9166666666667	691
1985.25	692
1985.5833333333333	692
1985.9166666666667	691
1986.1666666666667	693
1986.5	692
1986.8333333333333	691
1987.1666666666667	692
1987.4166666666667	693
1987.75	691
1988.0833333333333	691
1988.4166666666667	691
1988.6666666666667	690
1989	690
1989.3333333333333	691
1989.6666666666667	691
1989.9166666666667	691
1990.25	692
1990.5833333333333	691
1990.9166666666667	691
1991.1666666666667	691
1991.5	691
1991.8333333333333	690
1992.1666666666667	690
1992.4166666666667	690
1992.75	690
1993.0833333333333	690
1993.4166666666667	693
1993.6666666666667	692
1994	692
1994.3333333333333	693
1994.6666666666667	692
1995	692
1995.25	692
1995.5833333333333	692
1995.9166666666667	691
1996.25	693
1996.5	693
1996.8333333333333	692
1997.1666666666667	693
1997.5	692
1997.75	691
1998.0833333333333	691
1998.4166666666667	692
1998.75	691
1999	691
1999.3333333333333	693
1999.6666666666667	692
2000	691
2000.25	691
2000.5833333333333	691
2000.9166666666667	690
2001.25	693
2001.5	693
2001.8333333333333	691
2002.1666666666667	691
2002.5	690
2002.75	690
2003.0833333333333	689
2003.4166666666667	690
2003.75	689
2004	689
2004.3333333333333	692
2004.6666666666667	691
2005	691
2005.3333333333333	691
2005.5833333333333	690
2005.9166666666667	690
2006.25	690
2006.5833333333333	690
2006.8333333333333	690
2007.1666666666667	689
2007.5	689
2007.8333333333333	689
2008.0833333333333	688
2008.4166666666667	690
2008.75	690
2009.0833333333333	690
2009.3333333333333	693
2009.6666666666667	692
2010	691
2010.3333333333333	693
2010.5833333333333	692
2010.9166666666667	691
2011.25	693
2011.5833333333333	693
2011.8333333333333	691
2012.1666666666667	690
2012.5	690
2012.8333333333333	690
2013.0833333333333	690
2013.4166666666667	691
2013.75	693
2014.0833333333333	692
2014.3333333333333	693
2014.6666666666667	693
2015	691
2015.3333333333333	691
2015.5833333333333	692
2015.9166666666667	691
2016.25	691
2016.5833333333333	690
2016.9166666666667	690
2017.1666666666667	690
2017.5	690
2017.8333333333333	690
2018.1666666666667	690
2018.4166666666667	693
2018.75	692
2019.0833333333333	692
2019.4166666666667	693
2019.6666666666667	692
2020	691
2020.3333333333333	692
2020.6666666666667	692
2020.9166666666667	691
2021.25	690
2021.5833333333333	690
2021.9166666666667	689
2022.1666666666667	689
2022.5	691
2022.8333333333333	690
2023.1666666666667	690
2023.4166666666667	692
2023.75	692
2024.0833333333333	691
2024.4166666666667	691
2024.6666666666667	690
2025	690
2025.3333333333333	691
2025.6666666666667	691
2025.9166666666667	691
2026.25	691
2026.5833333333333	691

Rate and persistence

-0.86 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	98.6% 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 1951 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-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 2026-09-02, 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

899 monthly observations 1951–2026 Mm³

Spatially aggregatedHigh confidenceAugust 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 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	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	125
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	125
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	125
Oct	124	124
Nov	120	124
Dec	117	124