HydrionisGlobal Water Intelligence
Monitored reservoir

Bartlett Reservoir At Bartlett Dam, AZ

United States Geological Survey reservoir gauge 09509502 in AZ, with published storage from 1974.

Storage record09509502

Storage now, against this reservoir's own record

174.42 Mm³
Stored, September 2026
57th
Percentile among 52 Seps on record
+9.8%
Against the Sep 1991–2020 average
+87.0%
Change over the 12 months to 2026-09

Storage in September 2026 was around the middle of the Sep record, ranked against 52 other Seps held for this reservoir.

Storage, 1974–2026

Monthly mean storage
624 monthly values, 1974 to 2026
Monthly mean storageMonthly mean storage: Bartlett Reservoir At Bartlett Dam, AZ in Mm³, from 1974.75 to 2026.6666666666667.0100200Mm³1974.751981.251987.751994.252000.752007.252013.752020.25Year

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 624 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 624 would be longer than this page and unusable with a screen reader.
PeriodBartlett Reservoir At Bartlett Dam, AZ (Mm³)
October 197478.0
January 197555.6
March 197564.4
June 1975117
August 197589.6
November 197559.4
February 197664.2
April 1976148
July 1976114
September 197685.3
December 197674.8
March 19779.64
May 19770
August 19770
October 197736.3
January 197853.0
April 1978217
June 1978206
September 1978191
December 1978197
February 1979196
May 1979217
July 1979206
October 1979197
January 1980152
March 1980194
June 1980191
August 1980176
November 1980101
February 198174.8
April 1981138
July 198189.0
September 198172.9
December 1981101
March 1982200
May 1982209
August 1982140
October 1982130
January 1983170
April 1983217
June 1983207
September 1983183
November 1983195
February 1984187
May 1984203
July 1984172
October 1984185
January 1985181
March 1985208
June 1985200
August 1985207
November 1985207
February 1986206
April 1986215
July 1986208
September 1986206
December 1986201
March 1987210
May 1987215
August 1987205
October 1987195
January 1988152
April 1988212
June 1988202
September 1988206
November 1988196
February 1989170
May 1989161
July 1989136
October 198980.4
December 198938.2
March 199024.5
June 199043.2
August 199064.1
November 199081.8
February 199174.4
April 1991218
July 1991201
September 1991203
December 1991208
March 1992211
May 1992219
August 1992206
October 1992203
January 1993173
April 1993214
June 1993206
September 1993174
November 1993203
February 1994204
May 1994183
July 1994171
October 1994168
December 1994139
March 1995163
June 1995147
August 1995143
November 1995146
January 1996117
April 1996113
July 199669.1
September 199651.4
December 199633.7
February 199796.6
May 1997153
August 1997153
October 1997139
January 1998112
April 1998216
June 1998202
September 1998187
November 1998130
February 199982.5
May 199982.2
July 199985.7
October 199987.3
December 199990.1
March 200081.3
June 200089.5
August 200074.8
November 200088.6
January 2001116
April 2001184
July 2001191
September 2001197
December 200187.5
February 200292.7
May 2002106
August 200287.0
October 200292.6
January 200377.2
March 2003146
June 2003194
September 2003168
November 2003140
February 2004116
May 2004122
July 2004139
October 2004168
December 2004196
March 2005219
June 2005202
August 2005214
November 2005189
January 2006187
April 2006157
July 2006153
September 2006175
December 2006107
February 200786.3
May 200785.4
August 200796.2
October 2007107
January 2008203
March 2008218
June 2008202
September 2008217
November 2008112
February 2009161
April 2009218
July 2009212
October 2009155
December 200991.0
March 2010207
May 2010219
August 2010213
November 2010156
January 2011171
April 2011125
July 2011115
September 2011107
December 201199.3
February 201281.6
May 2012104
August 201297.9
October 2012111
January 2013132
March 2013193
June 2013217
September 2013216
November 2013181
February 2014128
April 201483.0
July 2014157
October 2014175
December 2014138
March 2015149
May 2015179
August 2015145
November 201592.6
January 2016100
April 201699.1
June 2016129
September 2016157
December 2016114
February 2017196
May 2017205
August 2017202
October 2017182
January 2018126
March 2018102
June 201897.3
September 201899.2
November 2018101
February 2019133
April 2019213
July 2019201
October 2019164
December 2019133
March 2020198
May 2020218
August 2020211
November 2020124
January 2021105
April 2021109
June 2021108
September 2021146
December 2021118
February 2022122
May 2022111
July 202299.6
October 2022112
January 2023138
March 2023194
June 2023209
September 2023132
November 2023130
February 2024110
April 2024142
July 2024145
October 2024143
December 2024110
March 2025115
May 2025112
August 202590.4
November 2025128
January 2026162
April 2026153
June 2026148
September 2026174

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 12.050100150200Mm³123456789101112Month1991–2020 average 1: 130 Mm³1991–2020 average 2: 139 Mm³1991–2020 average 3: 156 Mm³1991–2020 average 4: 165 Mm³1991–2020 average 5: 163 Mm³1991–2020 average 6: 162 Mm³1991–2020 average 7: 158 Mm³1991–2020 average 8: 157 Mm³1991–2020 average 9: 159 Mm³1991–2020 average 10: 151 Mm³1991–2020 average 11: 131 Mm³1991–2020 average 12: 126 Mm³Most recent 12 months 1: 162 Mm³Most recent 12 months 2: 172 Mm³Most recent 12 months 3: 138 Mm³Most recent 12 months 4: 153 Mm³Most recent 12 months 5: 145 Mm³Most recent 12 months 6: 148 Mm³Most recent 12 months 7: 159 Mm³Most recent 12 months 8: 166 Mm³Most recent 12 months 9: 174 Mm³Most recent 12 months 10: 111 Mm³Most recent 12 months 11: 128 Mm³Most recent 12 months 12: 177 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)
Jan130162
Feb139172
Mar156138
Apr165153
May163145
Jun162148
Jul158159
Aug157166
Sep159174
Oct151111
Nov131128
Dec126177

Why this page shows a volume and not a percentage

Rate and persistence

+6.76 Mm³
Mean change per month over 12 months
3 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

Bartlett Reservoir At Bartlett Dam, AZ
Gauge location
Bartlett Reservoir At Bartlett Dam, AZBartlett Reservoir At Bartlett Dam, AZ — 174.42 Mm³Bartlett Reservoir At Bartlett Dam, AZ — 174.42 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 held1974–2026
Completeness98.1% 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 1974 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), Bartlett Reservoir At Bartlett Dam, AZ reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usgs-09509502/

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 Bartlett Reservoir At Bartlett 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

624 monthly observations 1974–2026 Mm³
Spatially aggregatedHigh confidenceSeptember 2026

Source: USGS — National Water Information System, 09509502. 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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