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

76.95 Mm³
Stored, August 2026
12th
Percentile among 27 Augs on record
-11.0%
Against the Aug 1991–2020 average
-15.7%
Change over the 12 months to 2026-08

Storage in August 2026 was lower than most Augs on record, ranked against 27 other Augs held for this reservoir.

Storage, 1999–2026

Monthly mean storage
321 monthly values, 1999 to 2026
Monthly mean storageMonthly mean storage: Lake Hefner At Oklahoma City, OK in Mm³, from 1999.9166666666667 to 2026.5833333333333.0255075100Mm³1999.91666666666672003.33333333333332006.752010.16666666666672013.583333333333320172020.41666666666672023.8333333333333Year

Monthly means of the publisher's daily record. Volume, not percentage of capacity: without a capacity whose definition is stated, fullness cannot be computed.

View the data behind this chart
Underlying data
PeriodLake Hefner At Oklahoma City, OK (Mm³)
December 199980.3
January 200089.6
February 200086.9
March 200086.4
April 200091.3
May 200092.3
June 200091.0
July 200092.6
August 200086.0
September 200077.7
October 200074.2
November 200085.1
December 200082.8
January 200180.4
February 200179.1
March 200184.0
April 200181.5
May 200181.1
June 200191.1
July 200183.6
August 200175.7
September 200182.1
October 200191.4
November 200188.2
December 200184.9
January 200281.9
February 200280.1
March 200277.3
April 200277.1
May 200277.3
June 200288.2
July 200287.8
August 200282.6
September 200280.8
October 200286.0
November 200293.4
December 200294.3
January 200393.4
February 200390.9
March 200393.0
April 200390.4
May 200391.9
June 200394.9
July 200391.2
August 200383.3
September 200377.8
October 200380.8
November 200379.8
December 200377.5
January 200475.5
February 200474.4
March 200485.3
April 200492.4
May 200493.2
June 200491.8
July 200493.8
August 200492.7
September 200490.0
October 200489.8
November 200494.8
December 200492.9
January 200593.4
February 200591.1
March 200587.5
April 200582.5
May 200582.4
June 200591.8
July 200593.8
August 200591.9
September 200595.2
October 200593.4
November 200588.2
December 200583.5
January 200686.6
February 200687.4
March 200685.8
April 200684.1
May 200683.9
June 200679.5
July 200673.9
August 200679.0
September 200675.7
October 200669.0
November 200663.2
December 200659.4
January 200757.8
February 200768.8
March 200768.6
April 200785.9
May 200796.3
June 200796.7
July 200796.3
August 200796.5
September 200793.6
October 200790.3
November 200788.6
December 200784.4
January 200880.6
February 200881.4
March 200882.0
April 200884.8
May 200892.3
June 200893.7
July 200892.7
August 200892.2
September 200891.4
October 200892.9
November 200893.5
December 200893.0
January 200990.7
February 200990.5
March 200992.3
April 200989.2
May 200989.8
June 200992.6
July 200988.4
August 200984.2
September 200984.1
October 200990.2
November 200994.4
December 200993.9
January 201093.2
February 201093.8
March 201092.2
April 201090.8
May 201091.4
June 201092.1
July 201091.8
August 201089.9
September 201085.4
October 201081.2
November 201078.7
December 201083.7
January 201180.4
February 201176.7
March 201175.8
April 201172.2
May 201168.6
June 201178.9
July 201176.1
August 201167.3
September 201158.9
October 201155.8
November 201172.5
December 201176.2
January 201276.4
February 201278.1
March 201280.8
April 201286.8
May 201286.9
June 201283.6
July 201276.4
August 201267.5
September 201261.2
October 201259.2
November 201255.4
December 201251.9
January 201349.3
February 201360.7
March 201377.6
April 201383.4
May 201391.4
June 201398.2
July 201393.4
August 201396.3
September 201391.0
October 201387.8
November 201385.0
December 201381.6
January 201478.9
February 201476.2
March 201473.9
April 201470.2
May 201468.4
June 201475.7
July 201480.8
August 201478.5
September 201472.5
October 201467.7
November 201464.2
December 201461.1
January 201559.2
February 201558.4
March 201557.8
April 201559.3
May 201582.3
June 201595.8
July 201597.1
August 201594.6
September 201590.1
October 201585.3
November 201583.6
December 201590.9
January 201696.2
February 201695.4
March 201694.5
April 201694.3
May 201694.4
June 201693.2
July 201690.3
August 201685.8
September 201682.2
October 201678.8
November 201673.9
December 201669.4
January 201767.7
February 201769.3
March 201774.2
April 201791.9
May 201796.1
June 201796.0
July 201794.5
August 201794.1
September 201794.0
October 201793.4
November 201792.4
December 201788.5
January 201886.7
February 201886.4
March 201888.3
April 201886.7
May 201886.4
June 201883.3
July 201886.9
August 201887.4
September 201892.3
October 201897.2
November 201896.8
December 201897.1
January 201996.5
February 201995.9
March 201995.5
April 201993.8
May 201995.3
June 201995.3
July 201993.7
August 201994.4
September 201994.8
October 201994.2
November 201995.0
December 201994.2
January 202095.3
February 202094.5
March 202096.0
April 202095.5
May 202095.1
June 202094.7
July 202093.3
August 202095.9
September 202096.0
October 202092.8
November 202096.0
December 202095.7
January 202195.9
February 202193.7
March 202195.7
April 202195.4
May 202195.1
June 202195.3
July 202196.9
August 202194.8
September 202191.3
October 202188.6
November 202188.2
December 202187.3
January 202286.7
February 202287.1
March 202287.9
April 202289.6
May 202289.5
June 202294.4
July 202288.0
August 202280.3
September 202278.4
October 202273.3
November 202278.5
December 202279.6
January 202379.0
February 202378.1
March 202376.6
April 202373.8
May 202375.7
June 202383.9
July 202393.8
August 202393.1
September 202387.6
October 202385.0
November 202385.9
December 202385.9
January 202491.7
February 202494.2
March 202494.4
April 202494.6
May 202494.3
June 202492.5
July 202487.3
August 202485.0
September 202480.8
October 202473.9
November 202490.9
December 202494.3
January 202594.6
February 202593.9
March 202592.9
April 202593.5
May 202595.2
June 202595.4
July 202594.9
August 202591.3
September 202592.2
October 202588.9
November 202587.5
December 202589.5
January 202692.0
February 202693.1
March 202693.8
April 202693.8
May 202690.8
June 202687.1
July 202684.0
August 202676.9

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: 76.9 Mm³Most recent 12 months 9: 92.2 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
Aug86.576.9
Sep84.192.2
Oct83.488.9
Nov84.087.5
Dec82.689.5

Rate and persistence

-1.20 Mm³
Mean drawdown per month over 12 months
3 of 24
Months in the last two years 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 — 76.95 Mm³Lake Hefner At Oklahoma City, OK — 76.95 Mm³

Where this comes from

321 monthly observations 1999–2026 Mm³
Spatially aggregatedHigh confidenceAugust 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 25 August 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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