HydrionisGlobal Water Intelligence
Monitored reservoir

Florence Lk Nr Big C CA

United States Geological Survey reservoir gauge 11229600 in CA, with published storage from 1925.

Storage record11229600

Storage now, against this reservoir's own record

31.75 Mm³
Stored, September 2025
46th
Percentile among 100 Seps on record
+31.7%
Against the Sep 1991–2020 average
-10.4%
Change over the 12 months to 2025-09

Storage in September 2025 was around the middle of the Sep record, ranked against 100 other Seps held for this reservoir.

Storage, 1925–2025

Monthly mean storage
1,197 monthly values, 1925 to 2025
Monthly mean storageMonthly mean storage: Florence Lk Nr Big C CA in Mm³, from 1925.8333333333333 to 2025.6666666666667.0255075100Mm³1925.83333333333331938.333333333333319511963.519761988.520012013.5Year

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 1,197 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,197 would be longer than this page and unusable with a screen reader.
PeriodFlorence Lk Nr Big C CA (Mm³)
November 19250.503
April 19262.68
September 19261.44
February 19271.03
July 192775.6
December 19270.278
May 192828.9
October 19280.666
March 19290.681
August 192960.4
January 19300.673
June 193060.3
November 19300.437
April 19310.803
September 19310.735
February 19320.669
July 193280.2
December 19320.680
May 19331.23
October 193310.6
March 19340.318
August 19340.653
January 19350.160
June 193560.9
November 19350.535
April 19365.05
September 193647.8
February 19370.308
July 193779.4
December 19370.891
May 19387.09
October 193875.4
March 19390.298
August 193975.7
January 19402.27
June 194075.5
November 19400.192
April 19410.461
September 194164.2
February 19420.233
July 194279.5
December 19420.164
May 19436.32
October 194322.6
March 19440.850
August 194469.9
January 19450.246
June 194530.6
November 194577.5
April 19462.71
September 194647.2
February 19470.309
July 194775.3
December 19470.247
May 194810.1
October 194810.1
May 194911.5
October 194945.6
March 19500.353
August 195058.8
January 19510.409
June 195165.3
November 19510.380
April 19523.48
September 195267.3
February 19530.375
July 195377.4
December 19530.325
May 195423.4
October 195415.0
March 19550.467
August 195573.3
January 19568.76
June 195659.4
November 195613.1
April 19571.66
September 195753.7
February 19580.449
July 195878.9
December 19580.346
May 195910.5
October 19590.413
March 19600.424
August 196024.6
January 19610.293
June 196131.5
November 19610.316
April 19621.23
September 196236.9
February 19632.44
July 196379.0
December 19630.371
May 196411.0
October 19640.325
March 19650.451
August 196572.4
January 19660.438
June 196669.1
November 19660.358
April 19670.505
September 196767.1
February 19680.445
July 196847.3
December 19680.451
May 196938.9
October 196930.7
March 19700.505
August 197060.6
January 19710.458
June 197146.4
November 197156.4
April 19720.546
September 197238.8
February 19730.454
July 197373.8
December 19730.443
May 197413.4
October 197415.0
March 19750.440
August 197563.9
February 19760.319
July 197612.5
December 19760.306
May 19770.647
October 19770.463
March 19780.480
August 197879.1
January 19791.47
June 197971.0
November 19791.45
April 19802.24
September 198060.9
February 19811.15
July 198171.2
December 19811.18
May 198246.9
October 198256.7
March 19831.26
August 198378.3
January 19841.49
June 198475.3
November 198435.6
April 19855.89
September 198528.0
February 19861.68
July 198679.6
December 19861.30
May 198727.8
October 19871.34
March 19881.50
August 198828.7
January 19891.34
June 198949.1
November 19891.33
April 19902.17
September 19901.29
February 19911.33
July 199166.7
December 19911.33
May 199232.3
October 19926.53
March 19931.62
August 199367.0
January 19941.33
June 199458.3
November 19941.42
April 19951.71
September 199564.3
February 19965.29
July 199679.4
December 19961.73
May 199754.3
October 199713.2
March 19981.56
August 199876.5
January 19991.35
June 199967.9
November 19991.30
April 20001.84
September 200036.5
February 20011.54
July 200160.3
December 20012.46
May 200233.0
October 20025.01
March 20031.51
August 200342.6
January 20041.43
June 200470.5
November 20041.65
April 20051.73
September 200530.5
February 20061.52
July 200676.8
December 20061.19
May 200725.1
October 20075.41
March 20081.56
August 200862.1
January 20091.44
June 200973.5
November 20096.13
April 20106.07
September 201050.1
February 201135.8
July 201176.8
December 201147.3
May 201247.9
October 20122.55
March 20134.08
August 201329.4
January 20146.59
June 201457.9
November 20143.48
April 201515.0
September 201518.7
February 20168.24
July 201657.5
December 201611.9
May 201740.1
October 20171.36
March 20182.72
August 201841.1
January 20191.44
June 201961.1
November 201934.7
April 202014.3
September 202022.3
February 20217.21
July 202144.5
December 20216.06
May 202232.5
October 20221.44
March 202315.6
August 202369.3
January 202414.6
June 202474.4
November 202421.1
April 202514.3
September 202531.8

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 12.020406080Mm³123456789101112Month1991–2020 average 1: 6.80 Mm³1991–2020 average 2: 6.46 Mm³1991–2020 average 3: 5.79 Mm³1991–2020 average 4: 9.14 Mm³1991–2020 average 5: 32.1 Mm³1991–2020 average 6: 64.5 Mm³1991–2020 average 7: 63.9 Mm³1991–2020 average 8: 46.0 Mm³1991–2020 average 9: 24.1 Mm³1991–2020 average 10: 12.2 Mm³1991–2020 average 11: 8.48 Mm³1991–2020 average 12: 6.14 Mm³Most recent 12 months 1: 6.97 Mm³Most recent 12 months 2: 7.24 Mm³Most recent 12 months 3: 7.57 Mm³Most recent 12 months 4: 14.3 Mm³Most recent 12 months 5: 35.5 Mm³Most recent 12 months 6: 73.6 Mm³Most recent 12 months 7: 71.3 Mm³Most recent 12 months 8: 48.3 Mm³Most recent 12 months 9: 31.8 Mm³Most recent 12 months 10: 33.7 Mm³Most recent 12 months 11: 21.1 Mm³Most recent 12 months 12: 6.07 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)
Jan6.806.97
Feb6.467.24
Mar5.797.57
Apr9.1414.3
May32.135.5
Jun64.573.6
Jul63.971.3
Aug46.048.3
Sep24.131.8
Oct12.233.7
Nov8.4821.1
Dec6.146.07

Why this page shows a volume and not a percentage

Rate and persistence

-0.31 Mm³
Mean drawdown per month over 12 months
0 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

Florence Lk Nr Big C CA
Gauge location
Florence Lk Nr Big C CAFlorence Lk Nr Big C CA — 31.75 Mm³Florence Lk Nr Big C CA — 31.75 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 held1925–2025
Completeness98.8% 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.
Continuity99% of the months between 1925 and 2025 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), Florence Lk Nr Big C CA reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usgs-11229600/

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 Florence Lk Nr Big C CA 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

1,197 monthly observations 1925–2025 Mm³
Spatially aggregatedHigh confidenceSeptember 2025

Source: USGS — National Water Information System, 11229600. 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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