HydrionisGlobal Water Intelligence
Monitored reservoir

Keyhole Reservoir

Keyhole Reservoir is a federal reservoir operated by the United States Bureau of Reclamation in its Great Plains region, with published operating records from 1951.

Storage recordKeyhole Reservoir and Dam

Storage now, against this reservoir's own record

109.81 Mm³
Stored, August 2026
36th
Percentile among 75 Augs on record
-30.1%
Against the Aug 1991–2020 average
-22.6%
Change over the 12 months to 2026-08

Storage in August 2026 was around the middle of the Aug record, ranked against 75 other Augs held for this reservoir.

Storage, 1951–2026

Monthly mean storage
899 monthly values, 1951 to 2026
Monthly mean storageMonthly mean storage: Keyhole Reservoir in Mm³, from 1951.75 to 2026.5833333333333.0100200Mm³1951.751961.16666666666671970.583333333333319801989.41666666666671998.83333333333332008.252017.6666666666667Year

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 899 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 899 would be longer than this page and unusable with a screen reader.
PeriodKeyhole Reservoir (Mm³)
October 19510
February 19520
June 195218.3
September 195213.1
January 195311.7
May 195314.4
September 195313.4
December 195312.3
April 195412.1
August 195410.3
December 19548.17
March 195512.0
July 195539.7
November 195520.6
March 195628.2
June 195620.3
October 195615.7
February 195715.7
June 195719.1
September 195714.0
January 195813.4
May 195813.2
September 195811.4
December 195810.8
April 195916.1
August 195913.7
December 195912.0
March 196018.4
July 196019.9
November 196016.2
March 196116.9
June 196113.2
October 196110.2
February 196223.4
June 196266.1
October 196287.6
January 196385.6
May 1963101
September 1963104
January 196499.0
April 1964106
August 1964161
December 1964151
April 1965171
July 1965180
November 1965169
March 1966170
July 1966155
October 1966147
February 1967148
June 1967174
October 1967155
January 1968153
May 1968158
September 1968149
January 1969145
April 1969156
August 1969163
December 1969149
April 1970160
July 1970166
November 1970145
March 1971155
July 1971210
October 1971193
February 1972196
June 1972223
October 1972208
January 1973206
May 1973214
September 1973195
January 1974195
May 1974206
August 1974180
December 1974170
April 1975183
August 1975180
November 1975165
March 1976172
July 1976185
November 1976162
February 1977162
June 1977175
October 1977141
February 1978139
May 1978220
September 1978199
January 1979193
May 1979209
August 1979191
December 1979177
April 1980184
August 1980142
November 1980126
March 1981128
July 198169.3
November 198151.6
February 198253.0
June 198275.9
October 198270.8
February 198378.6
May 198384.6
September 198362.3
January 198463.2
May 198494.4
September 1984100
December 198497.9
April 1985102
August 198573.8
December 198568.6
March 198677.2
July 198688.9
November 198681.7
March 198799.0
June 1987114
October 198796.2
February 198895.7
June 198894.4
September 198866.5
January 198965.1
May 198974.7
September 198949.5
December 198949.7
April 199062.0
August 199045.0
December 199038.1
March 199138.9
July 199155.6
November 199136.9
March 199237.8
June 199232.8
October 199223.1
February 199323.1
June 199373.4
September 199384.8
January 199485.5
May 1994130
September 1994106
January 1995114
April 1995119
August 1995135
December 1995133
April 1996184
July 1996184
November 1996174
March 1997213
July 1997223
October 1997215
February 1998215
June 1998221
October 1998223
January 1999219
May 1999223
September 1999217
January 2000212
April 2000216
August 2000205
December 2000195
April 2001209
July 2001211
November 2001192
March 2002192
July 2002170
October 2002144
February 2003144
June 2003164
October 2003136
January 2004136
May 2004139
September 2004118
January 2005116
May 2005122
August 2005101
December 200589.0
April 200691.4
August 200672.6
November 200666.6
March 200769.6
July 200784.6
November 200771.5
February 200872.4
June 2008111
October 2008108
February 2009113
May 2009132
September 2009126
January 2010125
May 2010135
August 2010140
December 2010134
April 2011166
August 2011210
November 2011203
March 2012228
July 2012209
November 2012183
February 2013184
June 2013193
October 2013191
February 2014197
May 2014217
September 2014209
January 2015208
May 2015217
August 2015221
December 2015205
April 2016208
August 2016183
December 2016177
March 2017181
July 2017176
November 2017146
March 2018167
June 2018199
October 2018194
February 2019197
June 2019227
September 2019211
January 2020209
May 2020219
September 2020192
December 2020187
April 2021189
August 2021165
December 2021158
March 2022160
July 2022163
November 2022145
March 2023151
June 2023163
October 2023160
February 2024160
June 2024162
September 2024141
January 2025139
May 2025145
September 2025139
December 2025137
April 2026136
August 2026110

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: 145 Mm³1991–2020 average 2: 147 Mm³1991–2020 average 3: 155 Mm³1991–2020 average 4: 161 Mm³1991–2020 average 5: 163 Mm³1991–2020 average 6: 167 Mm³1991–2020 average 7: 163 Mm³1991–2020 average 8: 157 Mm³1991–2020 average 9: 152 Mm³1991–2020 average 10: 150 Mm³1991–2020 average 11: 150 Mm³1991–2020 average 12: 150 Mm³Most recent 12 months 1: 137 Mm³Most recent 12 months 2: 137 Mm³Most recent 12 months 3: 137 Mm³Most recent 12 months 4: 136 Mm³Most recent 12 months 5: 134 Mm³Most recent 12 months 6: 129 Mm³Most recent 12 months 7: 123 Mm³Most recent 12 months 8: 110 Mm³Most recent 12 months 9: 139 Mm³Most recent 12 months 10: 137 Mm³Most recent 12 months 11: 137 Mm³Most recent 12 months 12: 137 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)
Jan145137
Feb147137
Mar155137
Apr161136
May163134
Jun167129
Jul163123
Aug157110
Sep152139
Oct150137
Nov150137
Dec150137

Why this page shows a volume and not a percentage

Water level

Monthly mean water surface elevation
899 monthly values
Monthly mean water surface elevationMonthly mean water surface elevation: Keyhole Reservoir in m, from 1951.75 to 2026.5833333333333.05001,000m1951.751961.16666666666671970.583333333333319801989.41666666666671998.83333333333332008.252017.6666666666667Year

An elevation above a datum, not a depth of water and not a distance below the crest. Levels at different reservoirs are measured against different datums and must not be read against one another; this line is comparable only with its own history. Elevation and volume are not proportional either — a metre near the bottom of a reservoir holds far less water than a metre near the top, because the surface area grows with height.

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 899 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 899 would be longer than this page and unusable with a screen reader.
PeriodKeyhole Reservoir (m)
1951.750
1952.08333333333330
1952.41666666666671,236
1952.66666666666671,235
19531,235
1953.33333333333331,235
1953.66666666666671,235
1953.91666666666671,235
1954.251,235
1954.58333333333331,234
1954.91666666666671,234
1955.16666666666671,235
1955.51,239
1955.83333333333331,237
1956.16666666666671,238
1956.41666666666671,237
1956.751,236
1957.08333333333331,236
1957.41666666666671,236
1957.66666666666671,235
19581,235
1958.33333333333331,235
1958.66666666666671,235
1958.91666666666671,234
1959.251,236
1959.58333333333331,235
1959.91666666666671,235
1960.16666666666671,236
1960.51,236
1960.83333333333331,236
1961.16666666666671,236
1961.41666666666671,235
1961.751,234
1962.08333333333331,237
1962.41666666666671,242
1962.751,243
19631,243
1963.33333333333331,244
1963.66666666666671,244
19641,244
1964.251,244
1964.58333333333331,247
1964.91666666666671,246
1965.251,247
1965.51,247
1965.83333333333331,247
1966.16666666666671,247
1966.51,247
1966.751,246
1967.08333333333331,246
1967.41666666666671,247
1967.751,247
19681,247
1968.33333333333331,247
1968.66666666666671,246
19691,246
1969.251,247
1969.58333333333331,247
1969.91666666666671,246
1970.251,247
1970.51,247
1970.83333333333331,246
1971.16666666666671,247
1971.51,248
1971.751,248
1972.08333333333331,248
1972.41666666666671,249
1972.751,248
19731,248
1973.33333333333331,249
1973.66666666666671,248
19741,248
1974.33333333333331,248
1974.58333333333331,247
1974.91666666666671,247
1975.251,248
1975.58333333333331,247
1975.83333333333331,247
1976.16666666666671,247
1976.51,248
1976.83333333333331,247
1977.08333333333331,247
1977.41666666666671,247
1977.751,246
1978.08333333333331,246
1978.33333333333331,249
1978.66666666666671,248
19791,248
1979.33333333333331,248
1979.58333333333331,248
1979.91666666666671,247
1980.251,248
1980.58333333333331,246
1980.83333333333331,245
1981.16666666666671,245
1981.51,242
1981.83333333333331,241
1982.08333333333331,241
1982.41666666666671,243
1982.751,243
1983.08333333333331,243
1983.33333333333331,243
1983.66666666666671,242
19841,242
1984.33333333333331,244
1984.66666666666671,244
1984.91666666666671,244
1985.251,244
1985.58333333333331,243
1985.91666666666671,242
1986.16666666666671,243
1986.51,244
1986.83333333333331,243
1987.16666666666671,244
1987.41666666666671,245
1987.751,244
1988.08333333333331,244
1988.41666666666671,244
1988.66666666666671,242
19891,242
1989.33333333333331,243
1989.66666666666671,241
1989.91666666666671,241
1990.251,242
1990.58333333333331,240
1990.91666666666671,240
1991.16666666666671,240
1991.51,241
1991.83333333333331,239
1992.16666666666671,240
1992.41666666666671,239
1992.751,238
1993.08333333333331,238
1993.41666666666671,243
1993.66666666666671,243
19941,244
1994.33333333333331,246
1994.66666666666671,245
19951,245
1995.251,245
1995.58333333333331,246
1995.91666666666671,246
1996.251,248
1996.51,248
1996.83333333333331,248
1997.16666666666671,249
1997.51,249
1997.751,249
1998.08333333333331,249
1998.41666666666671,249
1998.751,249
19991,249
1999.33333333333331,249
1999.66666666666671,249
20001,249
2000.251,249
2000.58333333333331,249
2000.91666666666671,248
2001.251,249
2001.51,249
2001.83333333333331,248
2002.16666666666671,248
2002.51,247
2002.751,246
2003.08333333333331,246
2003.41666666666671,247
2003.751,246
20041,246
2004.33333333333331,246
2004.66666666666671,245
20051,245
2005.33333333333331,245
2005.58333333333331,244
2005.91666666666671,244
2006.251,244
2006.58333333333331,243
2006.83333333333331,243
2007.16666666666671,243
2007.51,244
2007.83333333333331,243
2008.08333333333331,243
2008.41666666666671,245
2008.751,245
2009.08333333333331,245
2009.33333333333331,246
2009.66666666666671,246
20101,246
2010.33333333333331,246
2010.58333333333331,247
2010.91666666666671,246
2011.251,247
2011.58333333333331,249
2011.83333333333331,249
2012.16666666666671,249
2012.51,249
2012.83333333333331,248
2013.08333333333331,248
2013.41666666666671,248
2013.751,248
2014.08333333333331,248
2014.33333333333331,249
2014.66666666666671,249
20151,249
2015.33333333333331,249
2015.58333333333331,249
2015.91666666666671,249
2016.251,249
2016.58333333333331,248
2016.91666666666671,248
2017.16666666666671,248
2017.51,248
2017.83333333333331,247
2018.16666666666671,248
2018.41666666666671,249
2018.751,248
2019.08333333333331,248
2019.41666666666671,249
2019.66666666666671,249
20201,249
2020.33333333333331,249
2020.66666666666671,248
2020.91666666666671,248
2021.251,248
2021.58333333333331,247
2021.91666666666671,247
2022.16666666666671,247
2022.51,247
2022.83333333333331,247
2023.16666666666671,247
2023.41666666666671,247
2023.751,247
2024.08333333333331,247
2024.41666666666671,247
2024.66666666666671,247
20251,246
2025.33333333333331,247
2025.66666666666671,246
2025.91666666666671,246
2026.251,246
2026.58333333333331,245

Rate and persistence

-2.68 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

Keyhole Reservoir
Gauge location
Keyhole ReservoirKeyhole Reservoir — 109.81 Mm³Keyhole Reservoir — 109.81 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 Bureau of Reclamation — Reservoir operations and Colorado River data · US Government work — public domain
How the values came to existMeasured
Period held1951–2026
Completeness98.6% 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 1951 and 2026 are held. Monthly means of the publisher's own daily record.
Last read from the publisher2026-09-01
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), Keyhole Reservoir reservoir records, accessed 2026-09-02, hydrionis.com/reservoirs/reservoir-usbr-388/

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 Keyhole Reservoir 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

899 monthly observations 1951–2026 Mm³
Spatially aggregatedHigh confidenceAugust 2026

Source: USBR — Reservoir operations and Colorado River data, RISE catalogue item 477. Licence: Open.

Method: Monthly mean of the daily values published by the Bureau of Reclamation in acre-feet, converted to Mm³. Months with fewer than 20 days of record are not published rather than averaged from a partial month.

Stored as a volume and not as a share of capacity: the operator publishes what is in the reservoir but not what it holds when full, so a percentage cannot be computed without inventing the denominator.

Retrieved 1 September 2026.

Monthly mean of the daily values published by the Bureau of Reclamation in acre-feet, converted to Mm³. Months with fewer than 20 days of record are not published rather than averaged from a partial month.

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