Fresno Reservoir — storage

Storage now, against this reservoir's own record

43.07 Mm³

Stored, August 2026

26th

Percentile among 79 Augs on record

-34.1%

Against the Aug 1991–2020 average

+14.4%

Change over the 12 months to 2026-08

Storage in August 2026 was lower than most Augs on record, ranked against 79 other Augs held for this reservoir.

Storage, 1947–2026

Monthly mean storage

947 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 947 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 947 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
September 1951	126
January 1952	106
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
August 1959	102
December 1959	104
April 1960	162
August 1960	59.7
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
July 1967	119
November 1967	92.3
March 1968	100
July 1968	118
November 1968	116
March 1969	117
July 1969	144
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
June 1975	151
October 1975	151
February 1976	139
June 1976	121
October 1976	88.3
February 1977	81.5
June 1977	57.8
October 1977	29.7
February 1978	22.3
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
May 1983	71.4
September 1983	44.2
January 1984	32.4
May 1984	52.7
September 1984	37.6
January 1985	15.5
May 1985	51.9
September 1985	52.4
January 1986	50.6
May 1986	131
September 1986	75.4
January 1987	77.9
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
April 1991	86.0
August 1991	96.8
December 1991	81.0
April 1992	109
August 1992	46.4
December 1992	36.5
April 1993	99.0
August 1993	122
December 1993	102
April 1994	126
August 1994	67.4
December 1994	65.0
April 1995	71.4
August 1995	106
December 1995	86.3
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
March 1999	59.0
July 1999	99.4
November 1999	56.4
March 2000	51.7
July 2000	43.0
November 2000	30.6
March 2001	19.9
July 2001	23.2
November 2001	16.5
March 2002	5.75
July 2002	92.0
November 2002	61.1
March 2003	71.6
July 2003	65.6
November 2003	30.2
March 2004	29.7
July 2004	80.4
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
February 2007	48.6
June 2007	115
October 2007	49.0
February 2008	37.2
June 2008	102
October 2008	70.3
February 2009	61.6
June 2009	104
October 2009	51.6
February 2010	45.5
June 2010	124
October 2010	87.2
February 2011	81.1
June 2011	126
October 2011	71.8
February 2012	74.4
June 2012	119
October 2012	61.2
February 2013	58.5
June 2013	120
October 2013	76.3
February 2014	68.1
June 2014	101
October 2014	84.7
January 2015	82.9
May 2015	104
September 2015	73.5
January 2016	68.5
May 2016	117
September 2016	71.8
January 2017	67.7
May 2017	108
September 2017	42.7
January 2018	49.1
May 2018	107
September 2018	44.8
January 2019	51.7
May 2019	111
September 2019	62.7
January 2020	78.1
May 2020	113
September 2020	23.1
January 2021	36.3
May 2021	87.5
September 2021	49.0
January 2022	41.3
May 2022	59.9
September 2022	32.0
December 2022	49.6
April 2023	87.1
August 2023	52.6
December 2023	28.5
April 2024	43.4
August 2024	34.5
December 2024	18.9
April 2025	51.6
August 2025	37.6
December 2025	38.3
April 2026	44.7
August 2026	43.1

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	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	43.1
Sep	59.0	47.2
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

947 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 947 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 947 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
1951.6666666666667	783
1952	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
1959.5833333333333	782
1959.9166666666667	782
1960.25	785
1960.5833333333333	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
1967.5	783
1967.8333333333333	782
1968.1666666666667	782
1968.5	783
1968.8333333333333	783
1969.1666666666667	783
1969.5	784
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
1975.4166666666667	785
1975.75	785
1976.0833333333333	784
1976.4166666666667	783
1976.75	781
1977.0833333333333	781
1977.4166666666667	779
1977.75	776
1978.0833333333333	776
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
1983.3333333333333	781
1983.6666666666667	779
1984	777
1984.3333333333333	779
1984.6666666666667	778
1985	775
1985.3333333333333	779
1985.6666666666667	779
1986	779
1986.3333333333333	785
1986.6666666666667	782
1987	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
1991.25	782
1991.5833333333333	783
1991.9166666666667	782
1992.25	784
1992.5833333333333	779
1992.9166666666667	778
1993.25	783
1993.5833333333333	785
1993.9166666666667	783
1994.25	785
1994.5833333333333	781
1994.9166666666667	781
1995.25	781
1995.5833333333333	784
1995.9166666666667	782
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
1999.1666666666667	780
1999.5	783
1999.8333333333333	780
2000.1666666666667	779
2000.5	779
2000.8333333333333	778
2001.1666666666667	776
2001.5	777
2001.8333333333333	776
2002.1666666666667	773
2002.5	784
2002.8333333333333	781
2003.1666666666667	782
2003.5	782
2003.8333333333333	778
2004.1666666666667	778
2004.5	783
2004.8333333333333	780
2005.1666666666667	780
2005.5	784
2005.8333333333333	781
2006.1666666666667	782
2006.5	783
2006.8333333333333	781
2007.0833333333333	780
2007.4166666666667	785
2007.75	780
2008.0833333333333	779
2008.4166666666667	784
2008.75	782
2009.0833333333333	781
2009.4166666666667	784
2009.75	780
2010.0833333333333	780
2010.4166666666667	785
2010.75	783
2011.0833333333333	783
2011.4166666666667	785
2011.75	782
2012.0833333333333	782
2012.4166666666667	785
2012.75	781
2013.0833333333333	781
2013.4166666666667	785
2013.75	783
2014.0833333333333	782
2014.4166666666667	784
2014.75	783
2015	783
2015.3333333333333	784
2015.6666666666667	783
2016	782
2016.3333333333333	785
2016.6666666666667	782
2017	782
2017.3333333333333	785
2017.6666666666667	780
2018	780
2018.3333333333333	785
2018.6666666666667	780
2019	781
2019.3333333333333	785
2019.6666666666667	782
2020	783
2020.3333333333333	785
2020.6666666666667	777
2021	779
2021.3333333333333	783
2021.6666666666667	780
2022	780
2022.3333333333333	781
2022.6666666666667	778
2022.9166666666667	781
2023.25	783
2023.5833333333333	781
2023.9166666666667	778
2024.25	780
2024.5833333333333	779
2024.9166666666667	776
2025.25	781
2025.5833333333333	779
2025.9166666666667	779
2026.25	780
2026.5833333333333	780

Rate and persistence

+0.45 Mm³

Mean change per month over 12 months

15 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	98.6% 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 1947 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-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 2026-09-02, 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

947 monthly observations 1947–2026 Mm³

Spatially aggregatedHigh confidenceAugust 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 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.