Shaver Lk — storage

Storage now, against this reservoir's own record

114.75 Mm³

Stored, September 2025

58th

Percentile among 99 Seps on record

-9.6%

Against the Sep 1991–2020 average

+10.7%

Change over the 12 months to 2025-09

Storage in September 2025 was around the middle of the Sep record, ranked against 99 other Seps held for this reservoir.

Storage, 1927–2025

Monthly mean storage

1,185 monthly values, 1927 to 2025

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 1,185 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,185 would be longer than this page and unusable with a screen reader.
Period	Shaver Lk Nr Big C CA (Mm³)
January 1927	1.26
June 1927	6.07
November 1927	5.59
April 1928	20.5
September 1928	55.3
February 1929	15.1
July 1929	86.8
December 1929	16.2
May 1930	50.6
October 1930	18.6
March 1931	12.1
July 1931	10.2
December 1931	7.57
May 1932	53.5
October 1932	98.4
March 1933	39.9
August 1933	120
January 1934	43.1
June 1934	36.5
November 1934	6.87
April 1935	12.2
September 1935	95.1
February 1936	29.0
July 1936	167
December 1936	42.0
May 1937	70.8
October 1937	74.0
March 1938	44.3
August 1938	165
January 1939	68.0
June 1939	90.5
November 1939	18.6
April 1940	35.7
August 1940	127
January 1941	38.4
June 1941	149
November 1941	76.2
April 1942	24.6
September 1942	106
February 1943	39.0
July 1943	148
December 1943	45.0
May 1944	79.2
October 1944	73.1
March 1945	20.3
August 1945	160
January 1946	33.4
June 1946	163
November 1946	66.1
April 1947	12.8
September 1947	74.4
February 1948	31.6
July 1948	163
December 1948	52.5
May 1949	90.8
September 1949	83.2
February 1950	43.1
July 1950	144
December 1950	83.1
May 1951	102
October 1951	88.0
March 1952	21.5
August 1952	159
January 1953	38.0
June 1953	125
November 1953	71.7
April 1954	36.8
September 1954	107
February 1955	33.1
July 1955	140
December 1955	80.6
May 1956	59.4
October 1956	118
March 1957	25.7
August 1957	118
January 1958	29.3
June 1958	138
October 1958	124
March 1959	23.9
August 1959	29.6
January 1960	30.1
June 1960	57.4
November 1960	13.4
April 1961	23.9
September 1961	16.6
February 1962	21.3
July 1962	159
December 1962	64.4
May 1963	108
October 1963	112
March 1964	49.1
August 1964	33.7
January 1965	42.1
June 1965	150
November 1965	89.3
April 1966	47.1
September 1966	93.0
February 1967	33.2
June 1967	91.3
November 1967	97.2
April 1968	38.4
September 1968	14.2
February 1969	44.9
July 1969	165
December 1969	105
May 1970	88.7
October 1970	89.9
March 1971	43.3
August 1971	133
January 1972	50.5
June 1972	87.4
November 1972	54.9
April 1973	22.9
September 1973	128
February 1974	56.0
July 1974	162
December 1974	62.9
May 1975	39.0
October 1975	99.3
March 1976	49.7
July 1976	59.6
December 1976	33.4
May 1977	39.0
October 1977	35.2
March 1978	40.3
August 1978	164
January 1979	81.2
June 1979	163
November 1979	88.1
April 1980	88.6
September 1980	123
February 1981	75.3
July 1981	145
December 1981	89.7
May 1982	131
October 1982	164
March 1983	114
August 1983	167
January 1984	81.7
June 1984	137
November 1984	55.6
April 1985	64.6
August 1985	82.4
January 1986	31.7
June 1986	166
November 1986	80.9
April 1987	75.3
September 1987	30.9
February 1988	15.8
July 1988	40.0
December 1988	23.4
May 1989	55.7
October 1989	64.4
March 1990	43.9
August 1990	35.0
January 1991	28.6
June 1991	92.7
November 1991	97.1
April 1992	69.3
September 1992	54.7
February 1993	62.6
July 1993	166
December 1993	129
April 1994	108
September 1994	101
February 1995	98.4
July 1995	158
December 1995	153
May 1996	149
October 1996	154
March 1997	131
August 1997	164
January 1998	109
June 1998	117
November 1998	149
April 1999	112
September 1999	144
February 2000	116
July 2000	164
December 2000	103
May 2001	147
October 2001	127
March 2002	105
August 2002	140
January 2003	138
May 2003	105
October 2003	154
March 2004	112
August 2004	137
January 2005	119
June 2005	145
November 2005	136
April 2006	129
September 2006	163
February 2007	112
July 2007	110
December 2007	103
May 2008	115
October 2008	106
March 2009	121
August 2009	132
January 2010	113
June 2010	138
November 2010	63.1
April 2011	126
September 2011	70.3
February 2012	7.05
June 2012	115
November 2012	102
April 2013	106
September 2013	105
February 2014	100
July 2014	106
December 2014	78.8
May 2015	83.8
October 2015	93.1
March 2016	96.0
August 2016	149
January 2017	120
June 2017	137
November 2017	103
April 2018	89.5
September 2018	145
February 2019	88.8
July 2019	145
December 2019	99.3
May 2020	99.4
October 2020	125
March 2021	125
July 2021	124
December 2021	55.5
May 2022	91.1
October 2022	102
March 2023	126
August 2023	159
January 2024	91.9
June 2024	156
November 2024	93.5
April 2025	126
September 2025	115

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	101	101
Feb	100	107
Mar	99.1	116
Apr	98.9	126
May	111	131
Jun	134	147
Jul	142	144
Aug	137	123
Sep	127	115
Oct	119	90.9
Nov	114	93.5
Dec	108	99.1

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.

Rate and persistence

+0.92 Mm³

Mean change 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

Shaver Lk Nr Big C CA

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 Geological Survey — National Water Information System · US Government work — public domain
How the values came to exist	Measured
Period held	1927–2025
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 1927 and 2025 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-usgs-11239500.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), Shaver Lk Nr Big C CA reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usgs-11239500/

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 Shaver Lk Nr Big C CA 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

1,185 monthly observations 1927–2025 Mm³

Spatially aggregatedHigh confidenceSeptember 2025

Source: USGS — National Water Information System, 11239500. Licence: Open.

Method: Monthly mean of daily reservoir storage published by the USGS in acre-feet and converted to millions of cubic metres. Months with fewer than 20 days of record are not published rather than averaged from a partial month.

Reservoir storage is managed as well as observed: a drawdown may reflect an operating rule, flood-control rule curve or scheduled release rather than a shortage. Compare a month against the same month in other years, and do not read a fall as a supply signal without knowing the operating regime.

Retrieved 1 October 2026.

Monthly mean of daily reservoir storage published by the USGS in acre-feet and converted to millions of cubic metres. Months with fewer than 20 days of record are not published rather than averaged from a partial month.