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

102.71 Mm³
Stored, September 2026
36th
Percentile among 75 Seps on record
-32.4%
Against the Sep 1991–2020 average
-25.9%
Change over the 12 months to 2026-09

Storage in September 2026 was around the middle of the Sep record, ranked against 75 other Seps held for this reservoir.

Storage, 1951–2026

Monthly mean storage
900 monthly values, 1951 to 2026
Monthly mean storageMonthly mean storage: Keyhole Reservoir in Mm³, from 1951.75 to 2026.6666666666667.0100200Mm³1951.751961.16666666666671970.583333333333319801989.41666666666671998.83333333333332008.252017.6666666666667Year

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 900 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 900 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
January 195910.8
April 195916.1
August 195913.7
December 195912.0
April 196027.7
July 196019.9
November 196016.2
March 196116.9
July 196111.1
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
August 1965177
November 1965169
March 1966170
July 1966155
November 1966146
February 1967148
June 1967174
October 1967155
February 1968153
May 1968158
September 1968149
January 1969145
May 1969169
August 1969163
December 1969149
April 1970160
August 1970154
November 1970145
March 1971155
July 1971210
November 1971194
February 1972196
June 1972223
October 1972208
February 1973206
June 1973213
September 1973195
January 1974195
May 1974206
September 1974174
December 1974170
April 1975183
August 1975180
December 1975165
March 1976172
July 1976185
November 1976162
March 1977164
June 1977175
October 1977141
February 1978139
June 1978215
September 1978199
January 1979193
May 1979209
September 1979185
January 1980177
April 1980184
August 1980142
December 1980126
April 1981124
July 198169.3
November 198151.6
March 198256.8
July 198275.6
October 198270.8
February 198378.6
June 198383.7
October 198362.7
January 198463.2
May 198494.4
September 1984100
January 198597.8
April 1985102
August 198573.8
December 198568.6
April 198681.3
August 198679.9
November 198681.7
March 198799.0
July 1987107
November 198795.7
February 198895.7
June 198894.4
October 198865.5
February 198965.1
May 198974.7
September 198949.5
January 199050.0
May 199065.3
August 199045.0
December 199038.1
April 199139.6
August 199145.2
November 199136.9
March 199237.8
July 199230.9
November 199222.9
March 199326.0
June 199373.4
October 199384.1
February 199490.4
June 1994128
September 1994106
January 1995114
May 1995130
September 1995132
December 1995133
April 1996184
August 1996179
December 1996174
March 1997213
July 1997223
November 1997213
March 1998219
June 1998221
October 1998223
February 1999220
June 1999231
October 1999214
January 2000212
May 2000217
September 2000199
January 2001196
April 2001209
August 2001203
December 2001191
April 2002193
July 2002170
November 2002143
March 2003153
July 2003161
October 2003136
February 2004137
June 2004135
October 2004116
January 2005116
May 2005122
September 200596.1
January 200689.4
May 200692.5
August 200672.6
December 200666.6
April 200773.5
August 200776.7
November 200771.5
March 200877.7
July 2008112
November 2008108
February 2009113
June 2009132
October 2009124
February 2010125
May 2010135
September 2010136
January 2011135
May 2011181
August 2011210
December 2011203
April 2012228
August 2012197
November 2012183
March 2013185
July 2013191
November 2013194
March 2014211
June 2014217
October 2014208
February 2015213
June 2015233
September 2015212
January 2016206
May 2016207
September 2016180
December 2016177
April 2017182
August 2017169
December 2017146
March 2018167
July 2018201
November 2018194
March 2019216
June 2019227
October 2019207
February 2020211
June 2020214
October 2020189
January 2021188
May 2021189
September 2021160
January 2022158
April 2022160
August 2022154
December 2022145
April 2023158
July 2023165
November 2023160
March 2024159
July 2024157
October 2024138
February 2025139
June 2025145
October 2025137
January 2026137
May 2026134
September 2026103

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: 103 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
Sep152103
Oct150137
Nov150137
Dec150137

Why this page shows a volume and not a percentage

Water level

Monthly mean water surface elevation
900 monthly values
Monthly mean water surface elevationMonthly mean water surface elevation: Keyhole Reservoir in m, from 1951.75 to 2026.6666666666667.05001,000m1951.751961.16666666666671970.583333333333319801989.41666666666671998.83333333333332008.252017.6666666666667Year

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 900 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 900 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
19591,234
1959.251,236
1959.58333333333331,235
1959.91666666666671,235
1960.251,238
1960.51,236
1960.83333333333331,236
1961.16666666666671,236
1961.51,235
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
1965.58333333333331,247
1965.83333333333331,247
1966.16666666666671,247
1966.51,247
1966.83333333333331,246
1967.08333333333331,246
1967.41666666666671,247
1967.751,247
1968.08333333333331,247
1968.33333333333331,247
1968.66666666666671,246
19691,246
1969.33333333333331,247
1969.58333333333331,247
1969.91666666666671,246
1970.251,247
1970.58333333333331,247
1970.83333333333331,246
1971.16666666666671,247
1971.51,248
1971.83333333333331,248
1972.08333333333331,248
1972.41666666666671,249
1972.751,248
1973.08333333333331,248
1973.41666666666671,249
1973.66666666666671,248
19741,248
1974.33333333333331,248
1974.66666666666671,247
1974.91666666666671,247
1975.251,248
1975.58333333333331,247
1975.91666666666671,247
1976.16666666666671,247
1976.51,248
1976.83333333333331,247
1977.16666666666671,247
1977.41666666666671,247
1977.751,246
1978.08333333333331,246
1978.41666666666671,249
1978.66666666666671,248
19791,248
1979.33333333333331,248
1979.66666666666671,248
19801,247
1980.251,248
1980.58333333333331,246
1980.91666666666671,245
1981.251,245
1981.51,242
1981.83333333333331,241
1982.16666666666671,241
1982.51,243
1982.751,243
1983.08333333333331,243
1983.41666666666671,243
1983.751,242
19841,242
1984.33333333333331,244
1984.66666666666671,244
19851,244
1985.251,244
1985.58333333333331,243
1985.91666666666671,242
1986.251,243
1986.58333333333331,243
1986.83333333333331,243
1987.16666666666671,244
1987.51,245
1987.83333333333331,244
1988.08333333333331,244
1988.41666666666671,244
1988.751,242
1989.08333333333331,242
1989.33333333333331,243
1989.66666666666671,241
19901,241
1990.33333333333331,242
1990.58333333333331,240
1990.91666666666671,240
1991.251,240
1991.58333333333331,240
1991.83333333333331,239
1992.16666666666671,240
1992.51,239
1992.83333333333331,238
1993.16666666666671,238
1993.41666666666671,243
1993.751,243
1994.08333333333331,244
1994.41666666666671,246
1994.66666666666671,245
19951,245
1995.33333333333331,246
1995.66666666666671,246
1995.91666666666671,246
1996.251,248
1996.58333333333331,248
1996.91666666666671,248
1997.16666666666671,249
1997.51,249
1997.83333333333331,249
1998.16666666666671,249
1998.41666666666671,249
1998.751,249
1999.08333333333331,249
1999.41666666666671,249
1999.751,249
20001,249
2000.33333333333331,249
2000.66666666666671,248
20011,248
2001.251,249
2001.58333333333331,248
2001.91666666666671,248
2002.251,248
2002.51,247
2002.83333333333331,246
2003.16666666666671,247
2003.51,247
2003.751,246
2004.08333333333331,246
2004.41666666666671,246
2004.751,245
20051,245
2005.33333333333331,245
2005.66666666666671,244
20061,244
2006.33333333333331,244
2006.58333333333331,243
2006.91666666666671,243
2007.251,243
2007.58333333333331,243
2007.83333333333331,243
2008.16666666666671,243
2008.51,245
2008.83333333333331,245
2009.08333333333331,245
2009.41666666666671,246
2009.751,246
2010.08333333333331,246
2010.33333333333331,246
2010.66666666666671,246
20111,246
2011.33333333333331,248
2011.58333333333331,249
2011.91666666666671,249
2012.251,249
2012.58333333333331,248
2012.83333333333331,248
2013.16666666666671,248
2013.51,248
2013.83333333333331,248
2014.16666666666671,249
2014.41666666666671,249
2014.751,249
2015.08333333333331,249
2015.41666666666671,249
2015.66666666666671,249
20161,249
2016.33333333333331,249
2016.66666666666671,248
2016.91666666666671,248
2017.251,248
2017.58333333333331,248
2017.91666666666671,247
2018.16666666666671,248
2018.51,249
2018.83333333333331,248
2019.16666666666671,249
2019.41666666666671,249
2019.751,249
2020.08333333333331,249
2020.41666666666671,249
2020.751,248
20211,248
2021.33333333333331,248
2021.66666666666671,247
20221,247
2022.251,247
2022.58333333333331,247
2022.91666666666671,247
2023.251,247
2023.51,247
2023.83333333333331,247
2024.16666666666671,247
2024.51,247
2024.751,246
2025.08333333333331,247
2025.41666666666671,247
2025.751,246
20261,246
2026.33333333333331,246
2026.66666666666671,245

Rate and persistence

-3.00 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 — 102.71 Mm³Keyhole Reservoir — 102.71 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
Completeness98.7% 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 publisher2026-10-01
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), Keyhole Reservoir reservoir records, accessed 2026-10-05, 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

900 monthly observations 1951–2026 Mm³
Spatially aggregatedHigh confidenceSeptember 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 October 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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