HydrionisGlobal Water Intelligence
Monitored reservoir

Lake Hefner At Oklahoma City, OK

United States Geological Survey reservoir gauge 07159550 in OK, with published storage from 1999.

Storage record07159550

Storage now, against this reservoir's own record

68.08 Mm³
Stored, September 2026
8th
Percentile among 27 Seps on record
-19.1%
Against the Sep 1991–2020 average
-26.1%
Change over the 12 months to 2026-09

Storage in September 2026 was lower than almost every other Sep on record, ranked against 27 other Seps held for this reservoir.

Storage, 1999–2026

Monthly mean storage
322 monthly values, 1999 to 2026
Monthly mean storageMonthly mean storage: Lake Hefner At Oklahoma City, OK in Mm³, from 1999.9166666666667 to 2026.6666666666667.0255075100Mm³1999.91666666666672003.33333333333332006.752010.16666666666672013.583333333333320172020.41666666666672023.8333333333333Year

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 322 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 322 would be longer than this page and unusable with a screen reader.
PeriodLake Hefner At Oklahoma City, OK (Mm³)
December 199980.3
January 200089.6
March 200086.4
April 200091.3
May 200092.3
July 200092.6
August 200086.0
September 200077.7
November 200085.1
December 200082.8
January 200180.4
March 200184.0
April 200181.5
May 200181.1
July 200183.6
August 200175.7
September 200182.1
November 200188.2
December 200184.9
February 200280.1
March 200277.3
April 200277.1
June 200288.2
July 200287.8
August 200282.6
October 200286.0
November 200293.4
December 200294.3
February 200390.9
March 200393.0
April 200390.4
June 200394.9
July 200391.2
August 200383.3
October 200380.8
November 200379.8
December 200377.5
February 200474.4
March 200485.3
April 200492.4
June 200491.8
July 200493.8
August 200492.7
October 200489.8
November 200494.8
December 200492.9
February 200591.1
March 200587.5
April 200582.5
June 200591.8
July 200593.8
August 200591.9
October 200593.4
November 200588.2
January 200686.6
February 200687.4
March 200685.8
May 200683.9
June 200679.5
July 200673.9
September 200675.7
October 200669.0
November 200663.2
January 200757.8
February 200768.8
March 200768.6
May 200796.3
June 200796.7
July 200796.3
September 200793.6
October 200790.3
November 200788.6
January 200880.6
February 200881.4
March 200882.0
May 200892.3
June 200893.7
July 200892.7
September 200891.4
October 200892.9
November 200893.5
January 200990.7
February 200990.5
March 200992.3
May 200989.8
June 200992.6
August 200984.2
September 200984.1
October 200990.2
December 200993.9
January 201093.2
February 201093.8
April 201090.8
May 201091.4
June 201092.1
August 201089.9
September 201085.4
October 201081.2
December 201083.7
January 201180.4
February 201176.7
April 201172.2
May 201168.6
June 201178.9
August 201167.3
September 201158.9
October 201155.8
December 201176.2
January 201276.4
February 201278.1
April 201286.8
May 201286.9
June 201283.6
August 201267.5
September 201261.2
October 201259.2
December 201251.9
January 201349.3
February 201360.7
April 201383.4
May 201391.4
July 201393.4
August 201396.3
September 201391.0
November 201385.0
December 201381.6
January 201478.9
March 201473.9
April 201470.2
May 201468.4
July 201480.8
August 201478.5
September 201472.5
November 201464.2
December 201461.1
January 201559.2
March 201557.8
April 201559.3
May 201582.3
July 201597.1
August 201594.6
September 201590.1
November 201583.6
December 201590.9
January 201696.2
March 201694.5
April 201694.3
May 201694.4
July 201690.3
August 201685.8
September 201682.2
November 201673.9
December 201669.4
January 201767.7
March 201774.2
April 201791.9
June 201796.0
July 201794.5
August 201794.1
October 201793.4
November 201792.4
December 201788.5
February 201886.4
March 201888.3
April 201886.7
June 201883.3
July 201886.9
August 201887.4
October 201897.2
November 201896.8
December 201897.1
February 201995.9
March 201995.5
April 201993.8
June 201995.3
July 201993.7
August 201994.4
October 201994.2
November 201995.0
December 201994.2
February 202094.5
March 202096.0
April 202095.5
June 202094.7
July 202093.3
August 202095.9
October 202092.8
November 202096.0
January 202195.9
February 202193.7
March 202195.7
May 202195.1
June 202195.3
July 202196.9
September 202191.3
October 202188.6
November 202188.2
January 202286.7
February 202287.1
March 202287.9
May 202289.5
June 202294.4
July 202288.0
September 202278.4
October 202273.3
November 202278.5
January 202379.0
February 202378.1
March 202376.6
May 202375.7
June 202383.9
July 202393.8
September 202387.6
October 202385.0
November 202385.9
January 202491.7
February 202494.2
March 202494.4
May 202494.3
June 202492.5
July 202487.3
September 202480.8
October 202473.9
December 202494.3
January 202594.6
February 202593.9
April 202593.5
May 202595.2
June 202595.4
August 202591.3
September 202592.2
October 202588.9
December 202589.5
January 202692.0
February 202693.1
April 202693.8
May 202690.8
June 202687.1
August 202675.9
September 202668.1

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 12.0255075100Mm³123456789101112Month1991–2020 average 1: 81.4 Mm³1991–2020 average 2: 81.7 Mm³1991–2020 average 3: 83.3 Mm³1991–2020 average 4: 85.0 Mm³1991–2020 average 5: 87.5 Mm³1991–2020 average 6: 90.4 Mm³1991–2020 average 7: 89.0 Mm³1991–2020 average 8: 86.5 Mm³1991–2020 average 9: 84.1 Mm³1991–2020 average 10: 83.4 Mm³1991–2020 average 11: 84.0 Mm³1991–2020 average 12: 82.6 Mm³Most recent 12 months 1: 92.0 Mm³Most recent 12 months 2: 93.1 Mm³Most recent 12 months 3: 93.8 Mm³Most recent 12 months 4: 93.8 Mm³Most recent 12 months 5: 90.8 Mm³Most recent 12 months 6: 87.1 Mm³Most recent 12 months 7: 84.0 Mm³Most recent 12 months 8: 75.9 Mm³Most recent 12 months 9: 68.1 Mm³Most recent 12 months 10: 88.9 Mm³Most recent 12 months 11: 87.5 Mm³Most recent 12 months 12: 89.5 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)
Jan81.492.0
Feb81.793.1
Mar83.393.8
Apr85.093.8
May87.590.8
Jun90.487.1
Jul89.084.0
Aug86.575.9
Sep84.168.1
Oct83.488.9
Nov84.087.5
Dec82.689.5

Why this page shows a volume and not a percentage

Rate and persistence

-2.01 Mm³
Mean drawdown per month over 12 months
4 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

Lake Hefner At Oklahoma City, OK
Gauge location
Lake Hefner At Oklahoma City, OKLake Hefner At Oklahoma City, OK — 68.08 Mm³Lake Hefner At Oklahoma City, OK — 68.08 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 held1999–2026
Completeness95.8% 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.
Continuity96% of the months between 1999 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), Lake Hefner At Oklahoma City, OK reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usgs-07159550/

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 Lake Hefner At Oklahoma City, OK 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

322 monthly observations 1999–2026 Mm³
Spatially aggregatedHigh confidenceSeptember 2026

Source: USGS — National Water Information System, 07159550. 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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