HydrionisGlobal Water Intelligence
Monitored reservoir

San Carlos Reservoir At Coolidge Dam, AZ

United States Geological Survey reservoir gauge 09469000 in AZ, with published storage from 1982.

Storage record09469000

Storage now, against this reservoir's own record

5.67 Mm³
Stored, September 2026
2nd
Percentile among 44 Seps on record
-96.6%
Against the Sep 1991–2020 average
-35.7%
Change over the 12 months to 2026-09

Storage in September 2026 was lower than almost every other Sep on record, ranked against 44 other Seps held for this reservoir.

Storage, 1982–2026

Monthly mean storage
528 monthly values, 1982 to 2026
Monthly mean storageMonthly mean storage: San Carlos Reservoir At Coolidge Dam, AZ in Mm³, from 1982.75 to 2026.6666666666667.05001,000Mm³1982.751988.251993.751999.252004.752010.252015.752021.25Year

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 528 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 528 would be longer than this page and unusable with a screen reader.
PeriodSan Carlos Reservoir At Coolidge Dam, AZ (Mm³)
October 1982102
December 1982154
February 1983376
May 1983857
July 1983786
September 1983690
November 19831,152
January 19841,135
April 19841,061
June 1984946
August 1984834
October 1984813
December 1984886
March 19851,181
May 19851,162
July 19851,012
September 1985852
November 1985974
February 19861,060
April 19861,107
June 1986991
August 1986812
November 1986801
January 1987902
March 1987958
May 1987960
July 1987778
October 1987611
December 1987629
February 1988690
April 1988643
June 1988563
September 1988458
November 1988530
January 1989551
March 1989514
May 1989407
August 1989143
October 198972.8
December 198970.2
February 199084.9
April 199066.5
July 199042.8
September 199055.4
November 199060.8
January 1991181
March 1991472
June 1991587
August 1991439
October 1991426
December 1991473
February 1992756
May 1992890
July 1992786
September 1992666
November 1992660
January 19931,093
April 1993927
June 1993836
August 1993658
October 1993626
January 1994651
March 1994634
May 1994558
July 1994399
September 1994250
December 1994479
February 1995955
April 19951,056
June 1995959
August 1995766
November 1995658
January 1996647
March 1996608
May 1996482
July 1996307
October 1996186
December 1996214
February 1997236
April 1997249
June 1997183
September 199755.7
November 199788.9
January 1998130
March 1998225
May 1998330
August 1998172
October 199897.3
December 199898.1
February 1999103
April 199976.6
July 199950.0
September 199980.8
November 199987.2
January 200091.6
March 200087.1
June 200039.9
August 200035.2
October 200049.6
December 2000289
March 2001328
May 2001306
July 2001204
September 2001126
November 200197.7
February 200286.9
April 200270.3
June 200264.6
August 200257.6
October 200255.8
January 200344.9
March 200350.6
May 200346.6
July 200340.4
September 200336.7
December 200334.8
February 200433.6
April 200439.1
June 200427.1
August 200424.1
November 200424.3
January 200577.0
March 2005523
May 2005509
July 2005399
October 2005272
December 2005246
February 2006220
April 2006187
June 2006107
September 2006291
November 2006339
January 2007333
March 2007349
May 2007302
August 2007187
October 2007166
December 2007200
February 2008418
April 2008429
July 2008309
September 2008281
November 2008266
January 2009276
April 2009227
June 2009144
August 200965.1
October 200919.2
December 200914.5
March 2010268
May 2010354
July 2010243
September 2010181
November 2010149
February 2011140
April 2011101
June 201147.3
August 20115.47
October 20117.29
January 201223.7
March 201230.2
May 201213.3
July 20121.93
September 20128.08
December 20124.58
February 201313.2
April 20139.98
June 20130.456
August 201316.7
November 2013149
January 2014159
March 2014134
May 201470.3
July 201418.4
October 201478.6
December 201491.8
February 2015157
April 2015160
June 201597.1
September 20159.23
November 201537.3
January 201694.1
March 2016132
June 201647.0
August 201619.1
October 201625.9
December 201640.3
February 2017218
May 2017256
July 2017164
September 2017119
November 201778.5
January 201874.9
April 201852.4
June 20185.02
August 20181.77
October 20189.98
December 201821.4
March 2019134
May 2019175
July 201995.3
September 201920.9
November 20198.15
February 2020113
April 2020255
June 2020197
August 202092.8
October 202036.4
January 202124.2
March 202110.8
May 20210.084
July 20211.85
September 202144.5
December 202128.6
February 202242.7
April 202217.9
June 20220.040
August 202226.1
November 2022213
January 2023361
March 2023561
May 2023639
August 2023491
October 2023423
December 2023405
February 2024427
April 2024451
July 2024343
September 2024250
November 2024208
January 2025198
March 2025184
June 202598.3
August 202526.9
October 202512.4
December 202515.2
February 202627.8
May 20263.19
July 20260.267
September 20265.67

The reservoir's year

Seasonal storage profile
Each calendar month's reference average, against the most recent year
Seasonal storage profileSeasonal storage profile: 1991–2020 average, Most recent 12 months in Mm³, from 1 to 12.0100200300400Mm³123456789101112Month1991–2020 average 1: 232 Mm³1991–2020 average 2: 274 Mm³1991–2020 average 3: 309 Mm³1991–2020 average 4: 305 Mm³1991–2020 average 5: 284 Mm³1991–2020 average 6: 251 Mm³1991–2020 average 7: 209 Mm³1991–2020 average 8: 180 Mm³1991–2020 average 9: 166 Mm³1991–2020 average 10: 165 Mm³1991–2020 average 11: 175 Mm³1991–2020 average 12: 189 Mm³Most recent 12 months 1: 20.1 Mm³Most recent 12 months 2: 27.8 Mm³Most recent 12 months 3: 25.9 Mm³Most recent 12 months 4: 15.2 Mm³Most recent 12 months 5: 3.19 Mm³Most recent 12 months 6: 0.409 Mm³Most recent 12 months 7: 0.267 Mm³Most recent 12 months 8: 1.53 Mm³Most recent 12 months 9: 5.67 Mm³Most recent 12 months 10: 12.4 Mm³Most recent 12 months 11: 14.4 Mm³Most recent 12 months 12: 15.2 Mm³
  • 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
Period1991–2020 average (Mm³)Most recent 12 months (Mm³)
Jan23220.1
Feb27427.8
Mar30925.9
Apr30515.2
May2843.19
Jun2510.409
Jul2090.267
Aug1801.53
Sep1665.67
Oct16512.4
Nov17514.4
Dec18915.2

Why this page shows a volume and not a percentage

Rate and persistence

-0.26 Mm³
Mean drawdown per month over 12 months
13 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

San Carlos Reservoir At Coolidge Dam, AZ
Gauge location
San Carlos Reservoir At Coolidge Dam, AZSan Carlos Reservoir At Coolidge Dam, AZ — 5.67 Mm³San Carlos Reservoir At Coolidge Dam, AZ — 5.67 Mm³

About this data

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 existMeasured
Period held1982–2026
Completeness97.8% 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.
Continuity98% of the months between 1982 and 2026 are held. Monthly means of the publisher's own daily record.
Last read from the publisher2026-10-01
RedistributionPermitted by the upstream licences
Commercial reusePermitted by the upstream licences. No Hydrionis access tier can widen this.
MethodologyHow this was produced

Use this data

Use this data

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), San Carlos Reservoir At Coolidge Dam, AZ reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usgs-09469000/

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 San Carlos Reservoir At Coolidge Dam, AZ 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

528 monthly observations 1982–2026 Mm³
Spatially aggregatedHigh confidenceSeptember 2026

Source: USGS — National Water Information System, 09469000. 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.

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