Rockport Reservoir, UT — storage

Storage now, against this reservoir's own record

33.98 Mm³

Stored, September 1990

10th

Percentile among 30 Seps on record

-30.1%

Change over the 12 months to 1990-09

Storage in September 1990 was lower than most Seps on record, ranked against 30 other Seps held for this reservoir.

No percentage departure from the Sep average is published here. No long-term average is held for this month, so there is nothing to compare with.

Storage, 1960–1990

Monthly mean storage

360 monthly values, 1960 to 1990

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 360 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 360 would be longer than this page and unusable with a screen reader.
Period	Rockport Reservoir Near Wanship, UT (Mm³)
October 1960	13.5
December 1960	18.0
January 1961	18.7
March 1961	20.4
April 1961	21.7
June 1961	19.0
July 1961	8.38
September 1961	3.53
October 1961	4.59
December 1961	12.3
January 1962	14.3
March 1962	24.4
April 1962	35.6
June 1962	66.5
July 1962	75.3
September 1962	53.0
October 1962	44.7
December 1962	39.8
January 1963	39.8
March 1963	40.0
April 1963	39.9
June 1963	61.7
July 1963	56.7
September 1963	41.8
October 1963	33.5
December 1963	32.1
January 1964	32.0
March 1964	31.6
April 1964	38.3
June 1964	76.5
July 1964	75.3
September 1964	64.4
October 1964	57.6
December 1964	47.3
January 1965	52.3
March 1965	43.7
April 1965	44.5
June 1965	72.2
July 1965	74.6
September 1965	72.7
October 1965	71.4
December 1965	65.8
January 1966	62.3
March 1966	56.1
April 1966	64.6
June 1966	72.3
July 1966	56.9
September 1966	32.5
October 1966	24.8
December 1966	19.0
January 1967	17.6
March 1967	21.3
April 1967	29.1
June 1967	71.0
July 1967	74.1
September 1967	65.0
October 1967	61.5
December 1967	66.7
January 1968	59.4
March 1968	54.8
April 1968	57.6
June 1968	71.9
July 1968	74.3
September 1968	71.1
October 1968	68.5
December 1968	64.8
January 1969	62.6
March 1969	46.9
April 1969	41.4
June 1969	71.4
July 1969	66.9
September 1969	49.0
October 1969	43.6
December 1969	35.2
January 1970	29.8
March 1970	23.9
April 1970	30.0
June 1970	70.4
July 1970	72.3
September 1970	52.0
October 1970	46.5
December 1970	36.1
January 1971	29.8
March 1971	25.3
April 1971	31.7
June 1971	63.5
July 1971	71.7
September 1971	57.7
October 1971	54.9
December 1971	47.5
January 1972	42.5
March 1972	33.8
April 1972	30.7
June 1972	75.9
July 1972	72.3
September 1972	56.6
October 1972	53.0
December 1972	42.9
January 1973	34.7
March 1973	28.5
April 1973	37.7
June 1973	76.1
July 1973	75.4
September 1973	72.4
October 1973	74.8
December 1973	75.1
January 1974	70.2
March 1974	64.3
April 1974	64.9
June 1974	74.7
July 1974	74.8
September 1974	63.3
October 1974	57.7
December 1974	48.5
January 1975	47.4
March 1975	40.5
April 1975	40.5
June 1975	63.0
July 1975	77.3
September 1975	72.1
October 1975	70.3
December 1975	63.2
January 1976	59.7
March 1976	54.4
April 1976	59.0
June 1976	74.6
July 1976	71.1
September 1976	56.7
October 1976	49.2
December 1976	34.4
January 1977	34.8
March 1977	34.7
April 1977	40.5
June 1977	45.2
July 1977	41.8
September 1977	27.4
October 1977	19.5
December 1977	21.4
January 1978	26.2
March 1978	37.5
April 1978	54.5
June 1978	73.7
July 1978	75.2
September 1978	65.4
October 1978	61.3
December 1978	51.4
January 1979	45.2
March 1979	36.2
April 1979	45.8
June 1979	73.5
July 1979	74.6
September 1979	59.5
October 1979	49.8
December 1979	41.1
January 1980	35.5
March 1980	26.3
April 1980	26.7
June 1980	69.6
July 1980	74.8
September 1980	63.0
October 1980	57.2
December 1980	50.3
January 1981	51.0
March 1981	56.9
April 1981	64.7
June 1981	76.7
July 1981	72.4
September 1981	57.9
October 1981	51.9
December 1981	46.5
January 1982	45.9
March 1982	35.7
April 1982	36.6
June 1982	68.9
July 1982	76.2
September 1982	71.2
October 1982	76.0
December 1982	74.6
January 1983	67.2
March 1983	58.7
April 1983	44.2
June 1983	78.2
July 1983	76.7
September 1983	65.1
October 1983	71.1
December 1983	69.9
January 1984	42.3
March 1984	33.1
April 1984	34.2
June 1984	72.7
July 1984	75.9
September 1984	74.6
October 1984	64.6
December 1984	60.9
January 1985	55.6
March 1985	37.1
April 1985	48.2
June 1985	76.9
July 1985	74.6
September 1985	62.1
October 1985	56.8
December 1985	50.0
January 1986	45.0
March 1986	42.4
April 1986	28.8
June 1986	72.6
July 1986	76.0
September 1986	70.1
October 1986	68.2
December 1986	60.7
January 1987	56.4
March 1987	51.3
April 1987	52.4
June 1987	74.7
July 1987	68.4
September 1987	48.6
October 1987	40.3
December 1987	32.7
January 1988	28.3
March 1988	37.2
April 1988	46.5
June 1988	72.3
July 1988	66.4
September 1988	46.3
October 1988	37.3
December 1988	23.5
January 1989	27.3
March 1989	41.2
April 1989	49.8
June 1989	71.8
July 1989	70.7
September 1989	48.6
October 1989	50.8
December 1989	49.7
January 1990	48.0
March 1990	47.3
April 1990	51.3
June 1990	65.2
July 1990	56.0
September 1990	34.0

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.

Rate and persistence

-1.22 Mm³

Mean drawdown per month over 12 months

8 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

Rockport Reservoir Near Wanship, UT

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 Geological Survey — National Water Information System · US Government work — public domain
How the values came to exist	Measured
Period held	1960–1990
Completeness	96.8% 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.
Continuity	97% of the months between 1960 and 1990 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-usgs-10129400.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), Rockport Reservoir Near Wanship, UT reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usgs-10129400/

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 Rockport Reservoir Near Wanship, UT 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

360 monthly observations 1960–1990 Mm³

Spatially aggregatedHigh confidenceSeptember 1990

Source: USGS — National Water Information System, 10129400. 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 1 October 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.