Potholes Reservoir — storage

Storage now, against this reservoir's own record

61.98 Mm³

Stored, September 2026

42nd

Percentile among 72 Seps on record

-7.1%

Against the Sep 1991–2020 average

+27.9%

Change over the 12 months to 2026-09

Storage in September 2026 was around the middle of the Sep record, ranked against 72 other Seps held for this reservoir.

Storage, 1953–2026

Monthly mean storage

806 monthly values, 1953 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 806 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 806 would be longer than this page and unusable with a screen reader.
Period	Potholes Reservoir (Mm³)
August 1953	13.3
November 1953	28.3
March 1954	43.8
January 1955	24.3
April 1955	48.5
August 1955	80.7
November 1955	98.9
March 1956	283
June 1956	278
September 1956	188
May 1958	255
August 1958	92.6
December 1958	173
April 1959	325
July 1959	197
November 1959	208
February 1960	289
May 1960	251
September 1960	79.9
January 1961	263
June 1961	198
October 1961	73.4
May 1962	188
August 1962	31.1
December 1962	184
June 1963	181
October 1963	72.1
January 1964	238
April 1964	252
August 1964	21.0
November 1964	106
February 1965	245
June 1965	124
October 1965	42.4
February 1966	267
June 1966	122
September 1966	45.3
January 1967	268
April 1967	304
July 1967	252
November 1967	237
February 1968	418
May 1968	316
September 1968	139
March 1969	450
July 1969	276
October 1969	180
February 1970	362
June 1970	269
September 1970	55.7
December 1970	217
April 1971	363
July 1971	157
November 1971	114
February 1972	288
May 1972	217
September 1972	42.1
December 1972	221
March 1973	369
July 1973	61.6
October 1973	135
January 1974	378
May 1974	391
August 1974	117
December 1974	267
March 1975	447
June 1975	294
October 1975	132
January 1976	345
April 1976	426
August 1976	110
January 1977	301
May 1977	405
August 1977	57.1
November 1977	220
March 1978	446
June 1978	340
September 1978	119
January 1979	328
April 1979	428
July 1979	143
November 1979	258
February 1980	442
June 1980	364
September 1980	134
December 1980	314
June 1981	335
September 1981	34.4
April 1982	366
August 1982	100
March 1983	409
July 1983	204
October 1983	120
March 1984	477
July 1984	223
October 1984	116
May 1985	327
September 1985	50.9
April 1986	431
July 1986	184
March 1987	398
June 1987	326
October 1987	44.0
May 1988	383
August 1988	87.3
February 1989	303
May 1989	449
August 1989	111
December 1989	227
March 1990	348
July 1990	203
October 1990	50.1
January 1991	252
May 1991	429
August 1991	92.3
November 1991	175
March 1992	371
June 1992	345
September 1992	86.3
January 1993	292
April 1993	425
August 1993	129
November 1993	154
February 1994	331
June 1994	368
September 1994	42.2
December 1994	272
April 1995	449
July 1995	250
October 1995	99.9
February 1996	391
May 1996	404
September 1996	35.2
December 1996	239
March 1997	436
July 1997	222
October 1997	117
January 1998	340
May 1998	326
August 1998	45.4
December 1998	229
March 1999	397
June 1999	341
October 1999	61.0
January 2000	285
April 2000	386
August 2000	131
November 2000	181
February 2001	348
June 2001	286
September 2001	52.9
January 2002	285
April 2002	378
July 2002	235
November 2002	126
February 2003	295
May 2003	457
September 2003	66.4
December 2003	209
April 2004	309
July 2004	264
October 2004	146
February 2005	387
May 2005	458
August 2005	76.7
December 2005	303
March 2006	418
June 2006	406
October 2006	88.7
January 2007	322
May 2007	437
August 2007	120
November 2007	224
March 2008	414
June 2008	414
September 2008	63.8
January 2009	331
April 2009	426
August 2009	79.1
November 2009	204
February 2010	374
June 2010	437
September 2010	76.8
December 2010	272
April 2011	407
July 2011	268
October 2011	68.0
February 2012	349
May 2012	449
September 2012	63.0
December 2012	267
March 2013	372
July 2013	245
October 2013	95.5
January 2014	301
May 2014	450
August 2014	106
December 2014	277
March 2015	375
June 2015	360
October 2015	86.6
January 2016	314
April 2016	405
August 2016	144
November 2016	259
February 2017	400
June 2017	335
September 2017	65.2
January 2018	350
April 2018	408
July 2018	199
November 2018	194
February 2019	358
May 2019	430
September 2019	88.8
December 2019	289
April 2020	331
July 2020	219
October 2020	92.7
February 2021	342
May 2021	311
August 2021	60.9
December 2021	252
March 2022	319
June 2022	409
October 2022	107
January 2023	337
May 2023	435
August 2023	74.6
November 2023	219
March 2024	382
June 2024	386
September 2024	55.6
January 2025	357
April 2025	443
August 2025	79.7
November 2025	246
February 2026	386
June 2026	406
September 2026	62.0

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	315	351
Feb	361	386
Mar	383	389
Apr	397	428
May	432	476
Jun	365	406
Jul	226	238
Aug	107	106
Sep	66.7	62.0
Oct	88.3	114
Nov	189	246
Dec	263	314

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

827 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 827 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 827 would be longer than this page and unusable with a screen reader.
Period	Potholes Reservoir (m)
1952.4166666666667	305
1952.6666666666667	310
1953	311
1953.3333333333333	310
1953.6666666666667	312
1953.9166666666667	313
1954.25	312
1954.5	310
1954.8333333333333	312
1955.0833333333333	313
1955.4166666666667	313
1955.6666666666667	314
1955.9166666666667	315
1956.25	318
1956.5	317
1958.1666666666667	317
1958.4166666666667	316
1958.75	314
1959.0833333333333	317
1959.4166666666667	317
1959.6666666666667	315
1960	317
1960.25	317
1960.5	315
1960.9166666666667	317
1961.3333333333333	317
1961.6666666666667	313
1962.25	317
1962.5833333333333	313
1962.8333333333333	315
1963.4166666666667	316
1963.6666666666667	314
1964	316
1964.25	317
1964.5833333333333	312
1964.8333333333333	314
1965.0833333333333	317
1965.4166666666667	315
1965.6666666666667	312
1966	316
1966.3333333333333	316
1966.6666666666667	313
1966.9166666666667	316
1967.25	317
1967.5	317
1967.8333333333333	316
1968.0833333333333	318
1968.3333333333333	317
1968.6666666666667	315
1969.1666666666667	319
1969.5	317
1969.75	316
1970.1666666666667	319
1970.4166666666667	317
1970.75	314
1971	317
1971.3333333333333	317
1971.5833333333333	313
1971.8333333333333	315
1972.1666666666667	317
1972.4166666666667	316
1972.75	314
1973	317
1973.3333333333333	316
1973.5833333333333	312
1973.9166666666667	317
1974.1666666666667	319
1974.5	316
1974.75	314
1975	318
1975.3333333333333	318
1975.5833333333333	315
1975.9166666666667	317
1976.1666666666667	319
1976.5	316
1976.75	314
1977.25	319
1977.5	316
1977.8333333333333	316
1978.0833333333333	318
1978.3333333333333	318
1978.6666666666667	315
1978.9166666666667	317
1979.25	318
1979.5	315
1979.8333333333333	317
1980.0833333333333	319
1980.4166666666667	318
1980.6666666666667	315
1981.1666666666667	319
1981.4166666666667	318
1981.75	314
1982.3333333333333	317
1982.5833333333333	314
1983.25	318
1983.5	316
1984	318
1984.25	319
1984.5833333333333	315
1985.1666666666667	319
1985.5	315
1985.75	314
1986.4166666666667	317
1986.6666666666667	313
1987.25	318
1987.5833333333333	314
1988.1666666666667	318
1988.5	316
1988.75	313
1989.25	318
1989.5	316
1989.8333333333333	315
1990.0833333333333	317
1990.4166666666667	318
1990.6666666666667	314
1990.9166666666667	316
1991.25	318
1991.5	316
1991.8333333333333	316
1992.0833333333333	318
1992.4166666666667	318
1992.6666666666667	314
1993	317
1993.25	318
1993.5833333333333	315
1993.8333333333333	315
1994.0833333333333	318
1994.4166666666667	318
1994.6666666666667	313
1995	318
1995.25	319
1995.5833333333333	315
1995.8333333333333	316
1996.1666666666667	319
1996.4166666666667	317
1996.75	313
1997	317
1997.25	319
1997.5833333333333	315
1997.8333333333333	316
1998.1666666666667	319
1998.4166666666667	316
1998.75	313
1999	317
1999.3333333333333	319
1999.5833333333333	314
1999.9166666666667	316
2000.1666666666667	318
2000.4166666666667	318
2000.75	314
2001	317
2001.3333333333333	318
2001.5833333333333	314
2001.9166666666667	316
2002.1666666666667	318
2002.5	316
2002.75	313
2003.0833333333333	317
2003.3333333333333	319
2003.6666666666667	314
2003.9166666666667	316
2004.1666666666667	317
2004.5	317
2004.75	315
2005.0833333333333	318
2005.3333333333333	319
2005.6666666666667	314
2005.9166666666667	317
2006.25	319
2006.5	317
2006.8333333333333	316
2007.0833333333333	318
2007.3333333333333	319
2007.6666666666667	314
2007.9166666666667	317
2008.25	318
2008.5	316
2008.8333333333333	316
2009.0833333333333	318
2009.4166666666667	318
2009.6666666666667	314
2010	318
2010.25	318
2010.5	317
2010.8333333333333	316
2011.0833333333333	318
2011.4166666666667	318
2011.6666666666667	313
2012	317
2012.25	318
2012.5833333333333	315
2012.8333333333333	316
2013.1666666666667	318
2013.4166666666667	318
2013.6666666666667	314
2014	317
2014.25	318
2014.5833333333333	314
2014.8333333333333	316
2015.1666666666667	318
2015.4166666666667	318
2015.75	314
2016	317
2016.3333333333333	319
2016.5833333333333	315
2016.8333333333333	317
2017.1666666666667	319
2017.4166666666667	318
2017.75	314
2018	318
2018.3333333333333	319
2018.5833333333333	314
2018.9166666666667	317
2019.1666666666667	318
2019.5	317
2019.75	314
2020.0833333333333	318
2020.3333333333333	318
2020.5833333333333	314
2020.9166666666667	317
2021.1666666666667	318
2021.5	315
2021.75	314
2022.0833333333333	317
2022.3333333333333	318
2022.6666666666667	313
2022.9166666666667	317
2023.25	318
2023.5	315
2023.75	314
2024.0833333333333	318
2024.3333333333333	319
2024.6666666666667	313
2024.9166666666667	317
2025.25	319
2025.5	316
2025.8333333333333	317
2026.0833333333333	318
2026.4166666666667	318
2026.6666666666667	313

Rate and persistence

+1.13 Mm³

Mean change per month over 12 months

1 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

Potholes 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	1953–2026
Completeness	90.8% 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	91% of the months between 1953 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-7265.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), Potholes Reservoir reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usbr-7265/

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 Potholes 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

806 monthly observations 1953–2026 Mm³

Spatially aggregatedHigh confidenceSeptember 2026

Source: USBR — Reservoir operations and Colorado River data, RISE catalogue item 132563. 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.