Howard Prairie Lake — storage

Storage now, against this reservoir's own record

38.02 Mm³

Stored, September 2026

32nd

Percentile among 61 Seps on record

-12.0%

Against the Sep 1991–2020 average

-36.2%

Change over the 12 months to 2026-09

Storage in September 2026 was around the middle of the Sep record, ranked against 61 other Seps held for this reservoir.

Storage, 1966–2026

Monthly mean storage

725 monthly values, 1966 to 2026

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 725 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 725 would be longer than this page and unusable with a screen reader.
Period	Howard Prairie Lake (Mm³)
May 1966	63.6
August 1966	51.8
November 1966	43.2
February 1967	42.3
May 1967	64.2
August 1967	66.2
November 1967	57.0
February 1968	47.6
May 1968	49.0
August 1968	34.9
November 1968	23.6
February 1969	24.3
May 1969	60.7
August 1969	63.6
November 1969	52.0
February 1970	67.3
May 1970	74.8
August 1970	64.9
December 1970	56.9
March 1971	71.2
June 1971	77.3
September 1971	64.2
December 1971	59.4
March 1972	77.9
June 1972	74.3
September 1972	62.3
December 1972	55.5
March 1973	56.7
June 1973	60.6
September 1973	46.4
December 1973	48.6
March 1974	74.8
June 1974	74.5
September 1974	61.6
December 1974	51.2
March 1975	52.1
June 1975	76.2
September 1975	63.7
December 1975	60.3
March 1976	64.9
June 1976	73.7
September 1976	61.2
December 1976	51.3
March 1977	43.0
June 1977	40.7
September 1977	28.4
December 1977	28.1
March 1978	49.8
June 1978	59.9
September 1978	49.2
December 1978	41.7
March 1979	47.2
July 1979	68.7
October 1979	58.3
January 1980	63.0
April 1980	76.2
July 1980	71.4
October 1980	59.6
January 1981	52.9
April 1981	54.5
July 1981	48.1
October 1981	35.7
January 1982	53.6
April 1982	76.5
July 1982	70.3
October 1982	57.3
January 1983	55.1
April 1983	75.9
July 1983	72.2
October 1983	61.9
January 1984	70.1
April 1984	77.9
July 1984	72.4
October 1984	61.9
January 1985	64.3
April 1985	73.2
July 1985	69.6
October 1985	57.9
January 1986	52.0
April 1986	74.8
July 1986	69.3
October 1986	57.1
January 1987	50.2
April 1987	55.5
July 1987	47.6
October 1987	39.1
February 1988	31.2
May 1988	33.1
August 1988	24.9
November 1988	15.9
February 1989	11.5
May 1989	47.5
August 1989	45.0
November 1989	38.4
February 1990	32.1
May 1990	41.7
August 1990	35.1
November 1990	29.9
February 1991	24.5
May 1991	36.1
August 1991	36.4
November 1991	27.6
February 1992	23.9
May 1992	20.5
August 1992	9.17
November 1992	8.21
February 1993	3.34
May 1993	38.9
August 1993	44.0
November 1993	41.0
February 1994	36.1
May 1994	32.9
August 1994	20.2
November 1994	14.6
February 1995	19.8
May 1995	58.7
August 1995	62.1
November 1995	52.0
February 1996	73.5
May 1996	76.2
September 1996	63.1
December 1996	67.3
March 1997	76.5
June 1997	74.4
September 1997	62.3
December 1997	54.8
March 1998	65.0
June 1998	76.4
September 1998	63.5
December 1998	60.5
March 1999	61.9
June 1999	74.0
September 1999	63.0
December 1999	53.4
March 2000	56.1
June 2000	71.2
September 2000	57.8
December 2000	48.1
March 2001	40.5
June 2001	41.2
September 2001	28.2
December 2001	21.4
March 2002	26.4
June 2002	43.3
September 2002	30.0
December 2002	22.2
March 2003	30.6
June 2003	51.3
September 2003	38.7
December 2003	31.1
March 2004	39.5
June 2004	63.3
September 2004	49.5
December 2004	43.7
April 2005	41.4
July 2005	49.4
October 2005	38.6
January 2006	57.0
April 2006	76.3
July 2006	70.6
October 2006	56.6
January 2007	61.3
April 2007	75.2
July 2007	67.6
October 2007	55.8
January 2008	54.9
April 2008	62.6
July 2008	71.8
October 2008	58.6
January 2009	54.6
April 2009	64.2
July 2009	70.3
October 2009	56.0
January 2010	50.1
April 2010	49.2
July 2010	56.2
October 2010	45.9
January 2011	46.8
April 2011	67.6
July 2011	72.3
October 2011	60.6
January 2012	55.3
April 2012	60.2
July 2012	64.4
October 2012	50.9
January 2013	47.6
April 2013	59.4
July 2013	54.7
November 2013	42.7
February 2014	40.4
May 2014	41.1
August 2014	26.7
November 2014	20.3
February 2015	30.0
May 2015	29.1
August 2015	15.7
November 2015	10.4
February 2016	22.4
May 2016	52.5
August 2016	41.2
November 2016	35.8
February 2017	43.4
May 2017	74.9
August 2017	63.7
November 2017	55.9
February 2018	48.1
May 2018	47.3
August 2018	32.8
November 2018	25.1
February 2019	21.5
May 2019	40.7
August 2019	29.9
November 2019	24.1
February 2020	21.9
May 2020	20.4
August 2020	9.27
November 2020	5.14
February 2021	6.53
May 2021	7.29
August 2021	2.98
November 2021	3.09
February 2022	4.80
June 2022	10.4
September 2022	4.54
December 2022	5.89
March 2023	14.2
June 2023	37.9
September 2023	25.8
December 2023	26.1
March 2024	31.2
June 2024	41.2
September 2024	30.5
December 2024	31.9
March 2025	47.4
June 2025	69.8
September 2025	59.6
December 2025	58.5
March 2026	59.4
June 2026	51.3
September 2026	38.0

The reservoir's year

Seasonal storage profile

Each calendar month's reference average, against the most recent year

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
Period	1991–2020 average (Mm³)	Most recent 12 months (Mm³)
Jan	40.6	59.4
Feb	42.0	57.7
Mar	45.1	59.4
Apr	51.6	58.5
May	56.2	55.6
Jun	55.4	51.3
Jul	51.8	46.8
Aug	47.3	41.8
Sep	43.2	38.0
Oct	40.6	58.2
Nov	39.7	58.4
Dec	39.3	58.5

Why this page shows a volume and not a percentage

Percentage full is a division, and the denominator is missing

“Percentage full” is the figure a drought is discussed in, and it is stored volume divided by capacity. Capacity is published on several different bases — gross, usable, live, and the figure at a particular spillway or licence condition — and dividing a stored volume by the wrong one produces a percentage confidently wrong by the ratio between them, at exactly the moment the number matters most.

Hydrionis holds storage measurements for this reservoir and does not hold a compatible authoritative capacity figure for it, so percentage full is not calculated. The volume above is what was actually measured. Where you need a percentage, take the publisher’s own capacity on its own stated basis and divide it yourself — the source is linked below, and knowing which basis you used is the whole point.

Water level

Monthly mean water surface elevation

706 monthly values

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 706 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 706 would be longer than this page and unusable with a screen reader.
Period	Howard Prairie Lake (m)
1967.9166666666667	1,377
1968.1666666666667	1,376
1968.4166666666667	1,375
1968.6666666666667	1,373
1968.9166666666667	1,371
1969.1666666666667	1,372
1969.4166666666667	1,379
1969.6666666666667	1,378
1969.9166666666667	1,376
1970.1666666666667	1,379
1970.3333333333333	1,380
1970.5833333333333	1,378
1970.8333333333333	1,377
1971.0833333333333	1,379
1971.3333333333333	1,380
1971.5833333333333	1,379
1971.8333333333333	1,377
1972.0833333333333	1,379
1972.3333333333333	1,380
1972.5833333333333	1,379
1972.8333333333333	1,377
1973.0833333333333	1,377
1973.3333333333333	1,378
1973.5833333333333	1,376
1973.8333333333333	1,375
1974.0833333333333	1,380
1974.3333333333333	1,380
1974.5833333333333	1,379
1974.8333333333333	1,377
1975.0833333333333	1,376
1975.25	1,377
1975.5	1,380
1975.75	1,378
1976	1,378
1976.25	1,379
1976.5	1,379
1976.75	1,377
1977	1,376
1977.25	1,375
1977.5	1,374
1977.75	1,372
1978	1,374
1978.25	1,377
1978.5	1,377
1978.75	1,376
1979	1,375
1979.25	1,377
1979.5	1,379
1979.75	1,378
1980	1,378
1980.1666666666667	1,380
1980.4166666666667	1,380
1980.6666666666667	1,378
1980.9166666666667	1,377
1981.1666666666667	1,377
1981.4166666666667	1,377
1981.6666666666667	1,374
1981.9166666666667	1,375
1982.1666666666667	1,380
1982.4166666666667	1,380
1982.6666666666667	1,378
1982.9166666666667	1,377
1983.1666666666667	1,379
1983.4166666666667	1,380
1983.6666666666667	1,378
1983.9166666666667	1,378
1984.1666666666667	1,380
1984.4166666666667	1,380
1984.6666666666667	1,378
1984.9166666666667	1,378
1985.0833333333333	1,378
1985.3333333333333	1,380
1985.5833333333333	1,378
1985.8333333333333	1,377
1986.0833333333333	1,377
1986.3333333333333	1,380
1986.5833333333333	1,378
1986.8333333333333	1,377
1987.0833333333333	1,376
1987.3333333333333	1,377
1987.5833333333333	1,375
1987.8333333333333	1,374
1988.0833333333333	1,373
1988.3333333333333	1,373
1988.5833333333333	1,372
1988.8333333333333	1,369
1989.0833333333333	1,368
1989.3333333333333	1,376
1989.5833333333333	1,375
1989.8333333333333	1,374
1990	1,373
1990.25	1,375
1990.5	1,374
1990.75	1,373
1991	1,372
1991.25	1,373
1991.5	1,375
1991.75	1,373
1992	1,372
1992.25	1,371
1992.5	1,368
1992.75	1,367
1993	1,366
1993.25	1,372
1993.5	1,376
1993.75	1,375
1994	1,374
1994.25	1,374
1994.5	1,372
1994.75	1,369
1994.9166666666667	1,368
1995.1666666666667	1,373
1995.4166666666667	1,378
1995.6666666666667	1,377
1995.9166666666667	1,377
1996.1666666666667	1,380
1996.4166666666667	1,380
1996.6666666666667	1,378
1996.9166666666667	1,379
1997.1666666666667	1,380
1997.4166666666667	1,380
1997.6666666666667	1,378
1997.9166666666667	1,377
1998.1666666666667	1,378
1998.4166666666667	1,380
1998.6666666666667	1,378
1998.9166666666667	1,378
1999.1666666666667	1,378
1999.4166666666667	1,380
1999.6666666666667	1,378
1999.8333333333333	1,377
2000.0833333333333	1,377
2000.3333333333333	1,379
2000.5833333333333	1,378
2000.8333333333333	1,376
2001.0833333333333	1,375
2001.3333333333333	1,375
2001.5833333333333	1,373
2001.8333333333333	1,371
2002.0833333333333	1,371
2002.3333333333333	1,375
2002.5833333333333	1,374
2002.8333333333333	1,371
2003.0833333333333	1,372
2003.3333333333333	1,376
2003.5833333333333	1,375
2003.8333333333333	1,373
2004.0833333333333	1,373
2004.3333333333333	1,378
2004.5833333333333	1,377
2004.75	1,376
2005	1,375
2005.25	1,375
2005.5	1,376
2005.75	1,374
2006	1,377
2006.25	1,380
2006.5	1,379
2006.75	1,377
2007	1,378
2007.25	1,380
2007.5	1,379
2007.75	1,377
2008	1,377
2008.25	1,378
2008.5	1,379
2008.75	1,378
2009	1,377
2009.25	1,378
2009.5	1,379
2009.6666666666667	1,378
2009.9166666666667	1,377
2010.1666666666667	1,376
2010.4166666666667	1,378
2010.6666666666667	1,376
2010.9166666666667	1,375
2011.1666666666667	1,377
2011.4166666666667	1,380
2011.6666666666667	1,378
2011.9166666666667	1,377
2012.1666666666667	1,377
2012.4166666666667	1,379
2012.6666666666667	1,377
2012.9166666666667	1,376
2013.1666666666667	1,376
2013.4166666666667	1,378
2013.6666666666667	1,375
2013.9166666666667	1,375
2014.1666666666667	1,375
2014.4166666666667	1,374
2014.5833333333333	1,372
2014.8333333333333	1,371
2015.0833333333333	1,373
2015.3333333333333	1,373
2015.5833333333333	1,369
2015.8333333333333	1,368
2016.0833333333333	1,371
2016.3333333333333	1,377
2016.5833333333333	1,375
2016.8333333333333	1,374
2017.0833333333333	1,375
2017.3333333333333	1,380
2017.5833333333333	1,378
2017.8333333333333	1,377
2018.0833333333333	1,376
2018.3333333333333	1,376
2018.5833333333333	1,373
2018.8333333333333	1,372
2019.0833333333333	1,371
2019.3333333333333	1,375
2019.5	1,374
2019.75	1,372
2020	1,371
2020.25	1,371
2020.5	1,369
2020.75	1,366
2021	1,366
2021.25	1,367
2021.5	1,365
2021.75	1,365
2022	1,365
2022.25	1,367
2022.5	1,367
2022.75	1,366
2023	1,368
2023.25	1,370
2023.5	1,373
2023.75	1,372
2024	1,372
2024.25	1,374
2024.4166666666667	1,375
2024.6666666666667	1,373
2024.9166666666667	1,373
2025.1666666666667	1,376
2025.4166666666667	1,379
2025.6666666666667	1,378
2025.9166666666667	1,378
2026.1666666666667	1,378
2026.4166666666667	1,376
2026.6666666666667	1,374

Rate and persistence

-1.79 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

Howard Prairie Lake

Gauge location

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 exist	Measured
Period held	1966–2026
Completeness	99.0% 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.
Continuity	99% of the months between 1966 and 2026 are held. Monthly means of the publisher's own daily record.
Last read from the publisher	2026-10-01
Redistribution	Permitted by the upstream licences
Commercial reuse	Permitted by the upstream licences. No Hydrionis access tier can widen this.
Methodology	How this was produced

Use this data

Machine-readable JSON /api/v1/observations/by-subject/reservoir-usbr-7182.json
How to cite this, and who you must credit
How these figures were produced
Request this at a different scale, format or geography

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), Howard Prairie Lake reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usbr-7182/

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 Howard Prairie Lake 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

725 monthly observations 1966–2026 Mm³

Spatially aggregatedHigh confidenceSeptember 2026

Source: USBR — Reservoir operations and Colorado River data, RISE catalogue item 130954. 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.