Fresno Reservoir — storage

Storage now, against this reservoir's own record

52.83 Mm³

Stored, September 2026

44th

Percentile among 79 Seps on record

-10.4%

Against the Sep 1991–2020 average

+12.0%

Change over the 12 months to 2026-09

Storage in September 2026 was around the middle of the Sep record, ranked against 79 other Seps held for this reservoir.

Storage, 1947–2026

Monthly mean storage

948 monthly values, 1947 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 948 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 948 would be longer than this page and unusable with a screen reader.
Period	Fresno Reservoir (Mm³)
October 1947	101
February 1948	90.0
June 1948	161
October 1948	105
February 1949	85.1
June 1949	71.9
October 1949	13.9
February 1950	9.28
June 1950	67.5
October 1950	62.6
February 1951	83.3
June 1951	122
October 1951	113
February 1952	105
May 1952	155
September 1952	73.6
January 1953	95.6
May 1953	146
September 1953	89.1
January 1954	94.2
May 1954	164
September 1954	118
January 1955	96.9
May 1955	166
September 1955	121
January 1956	87.8
May 1956	147
September 1956	101
January 1957	97.6
May 1957	161
September 1957	76.7
January 1958	72.8
May 1958	138
September 1958	44.8
January 1959	36.7
May 1959	165
September 1959	94.6
January 1960	103
May 1960	165
September 1960	51.8
December 1960	37.8
April 1961	53.5
August 1961	5.27
December 1961	21.4
April 1962	69.5
August 1962	71.0
December 1962	46.1
April 1963	70.0
August 1963	61.1
December 1963	55.4
April 1964	60.7
August 1964	59.8
December 1964	85.1
April 1965	150
August 1965	129
December 1965	109
April 1966	161
August 1966	110
December 1966	102
April 1967	163
August 1967	81.1
December 1967	88.7
April 1968	115
August 1968	92.5
December 1968	113
April 1969	169
August 1969	116
November 1969	96.1
March 1970	83.6
July 1970	124
November 1970	86.2
March 1971	108
July 1971	75.1
November 1971	58.3
March 1972	88.1
July 1972	119
November 1972	114
March 1973	101
July 1973	60.2
November 1973	16.4
March 1974	20.2
July 1974	149
November 1974	118
March 1975	96.9
July 1975	141
November 1975	132
March 1976	149
July 1976	123
November 1976	87.7
March 1977	87.4
July 1977	24.1
November 1977	28.6
March 1978	48.7
June 1978	150
October 1978	102
February 1979	88.8
June 1979	143
October 1979	63.1
February 1980	53.7
June 1980	99.3
October 1980	44.8
February 1981	49.0
June 1981	108
October 1981	47.4
February 1982	38.2
June 1982	159
October 1982	22.3
February 1983	14.7
June 1983	48.2
October 1983	42.9
February 1984	31.9
June 1984	11.0
October 1984	20.8
February 1985	12.9
June 1985	40.4
October 1985	57.6
February 1986	56.8
June 1986	127
October 1986	86.8
February 1987	78.5
May 1987	124
September 1987	85.6
January 1988	77.7
May 1988	96.7
September 1988	21.6
January 1989	9.92
May 1989	89.4
September 1989	50.5
January 1990	102
May 1990	127
September 1990	49.7
January 1991	65.1
May 1991	115
September 1991	78.6
January 1992	80.1
May 1992	71.2
September 1992	37.3
January 1993	33.0
May 1993	106
September 1993	119
January 1994	99.0
May 1994	128
September 1994	55.4
January 1995	62.8
May 1995	85.4
September 1995	76.6
January 1996	89.5
April 1996	131
August 1996	62.7
December 1996	81.2
April 1997	123
August 1997	75.3
December 1997	66.6
April 1998	91.3
August 1998	78.0
December 1998	61.6
April 1999	64.0
August 1999	67.7
December 1999	54.9
April 2000	75.5
August 2000	18.6
December 2000	27.4
April 2001	14.9
August 2001	27.9
December 2001	13.5
April 2002	12.3
August 2002	48.3
December 2002	63.5
April 2003	101
August 2003	33.4
December 2003	27.4
April 2004	44.2
August 2004	51.4
November 2004	51.0
March 2005	48.0
July 2005	108
November 2005	59.8
March 2006	64.5
July 2006	83.5
November 2006	53.9
March 2007	70.7
July 2007	95.4
November 2007	46.6
March 2008	36.5
July 2008	109
November 2008	69.8
March 2009	63.4
July 2009	83.6
November 2009	51.9
March 2010	50.6
July 2010	113
November 2010	86.2
March 2011	90.1
July 2011	107
November 2011	75.0
March 2012	82.2
July 2012	104
November 2012	62.1
March 2013	66.6
July 2013	108
October 2013	76.3
February 2014	68.1
June 2014	101
October 2014	84.7
February 2015	95.7
June 2015	93.2
October 2015	74.3
February 2016	71.5
June 2016	111
October 2016	72.6
February 2017	67.8
June 2017	84.2
October 2017	55.0
February 2018	46.1
June 2018	111
October 2018	54.2
February 2019	49.2
June 2019	104
October 2019	78.5
February 2020	76.8
June 2020	82.5
October 2020	19.3
February 2021	35.6
June 2021	80.2
October 2021	48.1
February 2022	38.4
May 2022	59.9
September 2022	32.0
January 2023	46.8
May 2023	111
September 2023	33.7
January 2024	26.5
May 2024	92.7
September 2024	27.9
January 2025	16.1
May 2025	49.4
September 2025	47.2
January 2026	36.9
May 2026	59.7
September 2026	52.8

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	60.0	36.9
Feb	59.4	35.4
Mar	68.7	36.5
Apr	88.3	44.7
May	97.8	59.7
Jun	97.4	50.0
Jul	91.0	74.5
Aug	65.4	42.8
Sep	59.0	52.8
Oct	61.5	43.3
Nov	62.0	40.0
Dec	61.0	38.3

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

948 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 948 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 948 would be longer than this page and unusable with a screen reader.
Period	Fresno Reservoir (m)
1947.75	782
1948.0833333333333	781
1948.4166666666667	785
1948.75	782
1949.0833333333333	781
1949.4166666666667	780
1949.75	774
1950.0833333333333	774
1950.4166666666667	780
1950.75	779
1951.0833333333333	781
1951.4166666666667	783
1951.75	783
1952.0833333333333	782
1952.3333333333333	785
1952.6666666666667	780
1953	782
1953.3333333333333	784
1953.6666666666667	781
1954	782
1954.3333333333333	785
1954.6666666666667	783
1955	782
1955.3333333333333	785
1955.6666666666667	783
1956	781
1956.3333333333333	784
1956.6666666666667	782
1957	782
1957.3333333333333	785
1957.6666666666667	780
1958	780
1958.3333333333333	784
1958.6666666666667	778
1959	777
1959.3333333333333	785
1959.6666666666667	782
1960	782
1960.3333333333333	785
1960.6666666666667	779
1960.9166666666667	777
1961.25	779
1961.5833333333333	773
1961.9166666666667	775
1962.25	780
1962.5833333333333	780
1962.9166666666667	778
1963.25	780
1963.5833333333333	779
1963.9166666666667	779
1964.25	779
1964.5833333333333	779
1964.9166666666667	781
1965.25	784
1965.5833333333333	784
1965.9166666666667	783
1966.25	785
1966.5833333333333	783
1966.9166666666667	782
1967.25	785
1967.5833333333333	781
1967.9166666666667	781
1968.25	783
1968.5833333333333	782
1968.9166666666667	783
1969.25	785
1969.5833333333333	783
1969.8333333333333	782
1970.1666666666667	781
1970.5	783
1970.8333333333333	781
1971.1666666666667	782
1971.5	780
1971.8333333333333	779
1972.1666666666667	781
1972.5	783
1972.8333333333333	783
1973.1666666666667	782
1973.5	779
1973.8333333333333	775
1974.1666666666667	775
1974.5	784
1974.8333333333333	783
1975.1666666666667	782
1975.5	784
1975.8333333333333	784
1976.1666666666667	784
1976.5	783
1976.8333333333333	781
1977.1666666666667	781
1977.5	776
1977.8333333333333	776
1978.1666666666667	778
1978.4166666666667	785
1978.75	782
1979.0833333333333	781
1979.4166666666667	784
1979.75	779
1980.0833333333333	779
1980.4166666666667	782
1980.75	778
1981.0833333333333	778
1981.4166666666667	782
1981.75	778
1982.0833333333333	777
1982.4166666666667	785
1982.75	776
1983.0833333333333	775
1983.4166666666667	779
1983.75	779
1984.0833333333333	777
1984.4166666666667	774
1984.75	776
1985.0833333333333	774
1985.4166666666667	778
1985.75	780
1986.0833333333333	780
1986.4166666666667	785
1986.75	782
1987.0833333333333	782
1987.3333333333333	785
1987.6666666666667	782
1988	782
1988.3333333333333	783
1988.6666666666667	776
1989	774
1989.3333333333333	783
1989.6666666666667	779
1990	783
1990.3333333333333	785
1990.6666666666667	779
1991	781
1991.3333333333333	784
1991.6666666666667	782
1992	782
1992.3333333333333	781
1992.6666666666667	778
1993	777
1993.3333333333333	784
1993.6666666666667	784
1994	783
1994.3333333333333	785
1994.6666666666667	780
1995	781
1995.3333333333333	782
1995.6666666666667	782
1996	783
1996.25	785
1996.5833333333333	780
1996.9166666666667	782
1997.25	785
1997.5833333333333	782
1997.9166666666667	781
1998.25	783
1998.5833333333333	782
1998.9166666666667	780
1999.25	781
1999.5833333333333	781
1999.9166666666667	780
2000.25	782
2000.5833333333333	776
2000.9166666666667	777
2001.25	775
2001.5833333333333	777
2001.9166666666667	775
2002.25	775
2002.5833333333333	780
2002.9166666666667	782
2003.25	784
2003.5833333333333	778
2003.9166666666667	777
2004.25	780
2004.5833333333333	780
2004.8333333333333	780
2005.1666666666667	780
2005.5	784
2005.8333333333333	781
2006.1666666666667	782
2006.5	783
2006.8333333333333	781
2007.1666666666667	782
2007.5	784
2007.8333333333333	780
2008.1666666666667	779
2008.5	785
2008.8333333333333	782
2009.1666666666667	781
2009.5	783
2009.8333333333333	780
2010.1666666666667	780
2010.5	785
2010.8333333333333	783
2011.1666666666667	783
2011.5	784
2011.8333333333333	782
2012.1666666666667	783
2012.5	784
2012.8333333333333	781
2013.1666666666667	782
2013.5	784
2013.75	783
2014.0833333333333	782
2014.4166666666667	784
2014.75	783
2015.0833333333333	784
2015.4166666666667	784
2015.75	783
2016.0833333333333	782
2016.4166666666667	785
2016.75	783
2017.0833333333333	782
2017.4166666666667	783
2017.75	781
2018.0833333333333	780
2018.4166666666667	785
2018.75	781
2019.0833333333333	780
2019.4166666666667	784
2019.75	783
2020.0833333333333	783
2020.4166666666667	783
2020.75	777
2021.0833333333333	779
2021.4166666666667	783
2021.75	780
2022.0833333333333	779
2022.3333333333333	781
2022.6666666666667	778
2023	780
2023.3333333333333	785
2023.6666666666667	779
2024	778
2024.3333333333333	784
2024.6666666666667	778
2025	776
2025.3333333333333	780
2025.6666666666667	780
2026	779
2026.3333333333333	782
2026.6666666666667	781

Rate and persistence

+0.47 Mm³

Mean change per month over 12 months

14 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

Fresno 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	1947–2026
Completeness	98.8% 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 1947 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-337.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), Fresno Reservoir reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usbr-337/

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 Fresno 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

948 monthly observations 1947–2026 Mm³

Spatially aggregatedHigh confidenceSeptember 2026

Source: USBR — Reservoir operations and Colorado River data, RISE catalogue item 354. 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.