HydrionisGlobal Water Intelligence
Monitored reservoir

Alcova Reservoir

Alcova Reservoir is a federal reservoir operated by the United States Bureau of Reclamation in its Great Plains region, with published operating records from 1945.

Storage recordAlcova Reservoir Dam and Powerplant

Storage now, against this reservoir's own record

223.09 Mm³
Stored, September 2026
86th
Percentile among 81 Seps on record
+0.4%
Against the Sep 1991–2020 average
+0.1%
Change over the 12 months to 2026-09

Storage in September 2026 was higher than most Seps on record, ranked against 81 other Seps held for this reservoir.

Storage, 1945–2026

Monthly mean storage
972 monthly values, 1945 to 2026
Monthly mean storageMonthly mean storage: Alcova Reservoir in Mm³, from 1945.75 to 2026.6666666666667.0100200Mm³1945.751955.91666666666671966.08333333333331976.251986.41666666666671996.58333333333332006.752016.9166666666667Year

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 972 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 972 would be longer than this page and unusable with a screen reader.
PeriodAlcova Reservoir (Mm³)
October 194541.7
February 194645.1
June 1946211
October 1946102
February 1947103
June 1947221
October 1947135
February 1948135
July 1948220
November 1948161
March 1949160
July 1949223
November 1949193
March 1950191
July 1950225
November 1950212
March 1951209
July 1951225
November 1951199
March 1952196
July 1952232
November 1952193
March 1953192
July 1953226
December 1953208
April 1954231
August 1954232
December 1954212
April 1955230
August 1955230
December 1955210
April 1956230
August 1956232
December 1956212
April 1957230
August 1957231
December 1957211
April 1958232
August 1958233
December 1958109
May 1959231
September 1959230
January 1960230
May 1960232
September 1960230
January 1961194
May 1961231
September 1961229
January 1962195
May 1962227
September 1962229
January 1963193
May 1963230
September 1963222
January 1964192
May 1964231
October 1964202
February 1965194
June 1965227
October 1965207
February 1966192
June 1966226
October 1966203
February 1967191
June 1967227
October 1967206
February 1968191
June 1968226
October 1968133
February 1969202
June 1969227
October 1969219
March 1970195
July 1970222
November 1970193
March 1971198
July 1971220
November 1971192
March 1972199
July 1972221
November 1972193
March 1973192
July 1973220
November 1973193
March 1974204
July 1974223
November 1974193
March 1975194
August 1975221
December 1975193
April 1976208
August 1976222
December 1976193
April 1977202
August 1977221
December 1977189
April 1978210
August 1978221
December 1978193
April 1979202
August 1979223
December 1979193
April 1980205
August 1980223
January 1981189
May 1981221
September 1981220
January 1982190
May 1982221
September 1982220
January 1983192
May 1983222
September 1983221
January 1984191
May 1984218
September 1984221
January 1985193
May 1985221
September 1985220
January 1986172
June 1986222
October 1986200
February 1987189
June 1987222
October 1987206
February 1988193
June 1988221
October 1988206
February 1989192
June 1989222
October 1989206
February 1990187
June 1990221
October 1990203
February 1991193
June 1991221
November 1991188
March 1992193
July 1992222
November 1992193
March 1993193
July 1993222
November 1993192
March 1994192
July 1994223
November 1994182
March 1995192
July 1995221
November 1995184
March 1996192
July 1996222
November 1996195
April 1997212
August 1997223
December 1997193
April 1998213
August 1998223
December 1998193
April 1999219
August 1999222
December 1999193
April 2000214
August 2000222
December 2000193
April 2001205
August 2001221
December 2001193
April 2002205
September 2002221
January 2003193
May 2003223
September 2003221
January 2004193
May 2004221
September 2004223
January 2005192
May 2005223
September 2005222
January 2006193
May 2006222
September 2006222
January 2007193
May 2007223
September 2007222
February 2008193
June 2008222
October 2008209
February 2009193
June 2009223
October 2009208
February 2010193
June 2010222
October 2010207
February 2011193
June 2011223
October 2011207
February 2012194
June 2012223
October 2012206
February 2013194
July 2013223
November 2013193
March 2014180
July 2014223
November 2014194
March 2015194
July 2015222
November 2015194
March 2016194
July 2016223
November 2016194
March 2017194
July 2017223
November 2017194
March 2018194
July 2018222
December 2018194
April 2019210
August 2019222
December 2019194
April 2020211
August 2020223
December 2020134
April 2021210
August 2021223
December 2021194
April 2022211
August 2022223
December 2022194
April 2023210
August 2023223
December 2023194
May 2024223
September 2024223
January 2025194
May 2025223
September 2025223
January 2026194
May 2026223
September 2026223

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 12.0100200Mm³123456789101112Month1991–2020 average 1: 192 Mm³1991–2020 average 2: 193 Mm³1991–2020 average 3: 193 Mm³1991–2020 average 4: 210 Mm³1991–2020 average 5: 222 Mm³1991–2020 average 6: 223 Mm³1991–2020 average 7: 222 Mm³1991–2020 average 8: 223 Mm³1991–2020 average 9: 222 Mm³1991–2020 average 10: 204 Mm³1991–2020 average 11: 190 Mm³1991–2020 average 12: 191 Mm³Most recent 12 months 1: 194 Mm³Most recent 12 months 2: 194 Mm³Most recent 12 months 3: 194 Mm³Most recent 12 months 4: 209 Mm³Most recent 12 months 5: 223 Mm³Most recent 12 months 6: 223 Mm³Most recent 12 months 7: 223 Mm³Most recent 12 months 8: 223 Mm³Most recent 12 months 9: 223 Mm³Most recent 12 months 10: 206 Mm³Most recent 12 months 11: 194 Mm³Most recent 12 months 12: 194 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)
Jan192194
Feb193194
Mar193194
Apr210209
May222223
Jun223223
Jul222223
Aug223223
Sep222223
Oct204206
Nov190194
Dec191194

Why this page shows a volume and not a percentage

Water level

Monthly mean water surface elevation
972 monthly values
Monthly mean water surface elevationMonthly mean water surface elevation: Alcova Reservoir in m, from 1945.75 to 2026.6666666666667.1,6401,6501,6601,6701,680m1945.751955.91666666666671966.08333333333331976.251986.41666666666671996.58333333333332006.752016.9166666666667Year

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 972 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 972 would be longer than this page and unusable with a screen reader.
PeriodAlcova Reservoir (m)
1945.751,649
1946.08333333333331,650
1946.41666666666671,674
1946.751,660
1947.08333333333331,660
1947.41666666666671,675
1947.751,665
1948.08333333333331,665
1948.51,675
1948.83333333333331,668
1949.16666666666671,668
1949.51,675
1949.83333333333331,672
1950.16666666666671,672
1950.51,675
1950.83333333333331,674
1951.16666666666671,674
1951.51,675
1951.83333333333331,673
1952.16666666666671,672
1952.51,676
1952.83333333333331,672
1953.16666666666671,672
1953.51,676
1953.91666666666671,674
1954.251,676
1954.58333333333331,676
1954.91666666666671,674
1955.251,676
1955.58333333333331,676
1955.91666666666671,674
1956.251,676
1956.58333333333331,676
1956.91666666666671,674
1957.251,676
1957.58333333333331,676
1957.91666666666671,674
1958.251,676
1958.58333333333331,676
1958.91666666666671,661
1959.33333333333331,676
1959.66666666666671,676
19601,676
1960.33333333333331,676
1960.66666666666671,676
19611,672
1961.33333333333331,676
1961.66666666666671,676
19621,672
1962.33333333333331,676
1962.66666666666671,676
19631,672
1963.33333333333331,676
1963.66666666666671,675
19641,672
1964.33333333333331,676
1964.751,673
1965.08333333333331,672
1965.41666666666671,676
1965.751,674
1966.08333333333331,672
1966.41666666666671,676
1966.751,673
1967.08333333333331,672
1967.41666666666671,676
1967.751,674
1968.08333333333331,672
1968.41666666666671,676
1968.751,665
1969.08333333333331,673
1969.41666666666671,676
1969.751,675
1970.16666666666671,672
1970.51,676
1970.83333333333331,673
1971.16666666666671,673
1971.51,676
1971.83333333333331,673
1972.16666666666671,673
1972.51,676
1972.83333333333331,673
1973.16666666666671,673
1973.51,676
1973.83333333333331,673
1974.16666666666671,674
1974.51,676
1974.83333333333331,673
1975.16666666666671,673
1975.58333333333331,676
1975.91666666666671,673
1976.251,674
1976.58333333333331,676
1976.91666666666671,673
1977.251,674
1977.58333333333331,676
1977.91666666666671,672
1978.251,675
1978.58333333333331,676
1978.91666666666671,673
1979.251,674
1979.58333333333331,676
1979.91666666666671,673
1980.251,674
1980.58333333333331,676
19811,672
1981.33333333333331,676
1981.66666666666671,676
19821,673
1982.33333333333331,676
1982.66666666666671,676
19831,673
1983.33333333333331,676
1983.66666666666671,676
19841,673
1984.33333333333331,675
1984.66666666666671,676
19851,673
1985.33333333333331,676
1985.66666666666671,676
19861,670
1986.41666666666671,676
1986.751,674
1987.08333333333331,672
1987.41666666666671,676
1987.751,674
1988.08333333333331,673
1988.41666666666671,676
1988.751,674
1989.08333333333331,673
1989.41666666666671,676
1989.751,674
1990.08333333333331,672
1990.41666666666671,676
1990.751,674
1991.08333333333331,673
1991.41666666666671,676
1991.83333333333331,672
1992.16666666666671,673
1992.51,676
1992.83333333333331,673
1993.16666666666671,673
1993.51,676
1993.83333333333331,673
1994.16666666666671,673
1994.51,676
1994.83333333333331,672
1995.16666666666671,673
1995.51,676
1995.83333333333331,672
1996.16666666666671,673
1996.51,676
1996.83333333333331,673
1997.251,675
1997.58333333333331,676
1997.91666666666671,673
1998.251,675
1998.58333333333331,676
1998.91666666666671,673
1999.251,676
1999.58333333333331,676
1999.91666666666671,673
2000.251,675
2000.58333333333331,676
2000.91666666666671,673
2001.251,674
2001.58333333333331,676
2001.91666666666671,673
2002.251,674
2002.66666666666671,676
20031,673
2003.33333333333331,676
2003.66666666666671,676
20041,673
2004.33333333333331,676
2004.66666666666671,676
20051,673
2005.33333333333331,676
2005.66666666666671,676
20061,673
2006.33333333333331,676
2006.66666666666671,676
20071,673
2007.33333333333331,676
2007.66666666666671,676
2008.08333333333331,673
2008.41666666666671,676
2008.751,675
2009.08333333333331,673
2009.41666666666671,676
2009.751,674
2010.08333333333331,673
2010.41666666666671,676
2010.751,674
2011.08333333333331,673
2011.41666666666671,676
2011.751,674
2012.08333333333331,673
2012.41666666666671,676
2012.751,674
2013.08333333333331,673
2013.51,676
2013.83333333333331,673
2014.16666666666671,671
2014.51,676
2014.83333333333331,673
2015.16666666666671,673
2015.51,676
2015.83333333333331,673
2016.16666666666671,673
2016.51,676
2016.83333333333331,673
2017.16666666666671,673
2017.51,676
2017.83333333333331,673
2018.16666666666671,673
2018.51,676
2018.91666666666671,673
2019.251,675
2019.58333333333331,676
2019.91666666666671,673
2020.251,675
2020.58333333333331,676
2020.91666666666671,666
2021.251,675
2021.58333333333331,676
2021.91666666666671,673
2022.251,675
2022.58333333333331,676
2022.91666666666671,673
2023.251,675
2023.58333333333331,676
2023.91666666666671,673
2024.33333333333331,676
2024.66666666666671,676
20251,673
2025.33333333333331,676
2025.66666666666671,676
20261,673
2026.33333333333331,676
2026.66666666666671,676

Rate and persistence

+0.01 Mm³
Mean change 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

Alcova Reservoir
Gauge location
Alcova ReservoirAlcova Reservoir — 223.09 Mm³Alcova Reservoir — 223.09 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 held1945–2026
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 1945 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), Alcova Reservoir reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usbr-259/

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 Alcova 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

972 monthly observations 1945–2026 Mm³
Spatially aggregatedHigh confidenceSeptember 2026

Source: USBR — Reservoir operations and Colorado River data, RISE catalogue item 113. 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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