Rimrock Lake — storage

Storage now, against this reservoir's own record

143.90 Mm³

Stored, September 2026

56th

Percentile among 102 Seps on record

+1.9%

Against the Sep 1991–2020 average

+80.8%

Change over the 12 months to 2026-09

Storage in September 2026 was around the middle of the Sep record, ranked against 102 other Seps held for this reservoir.

Storage, 1925–2026

Monthly mean storage

1,217 monthly values, 1925 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 1,217 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,217 would be longer than this page and unusable with a screen reader.
Period	Rimrock Lake (Mm³)
May 1925	118
October 1925	21.5
March 1926	90.8
August 1926	62.6
January 1927	71.6
June 1927	219
December 1927	199
May 1928	231
October 1928	108
March 1929	115
August 1929	180
January 1930	27.5
June 1930	166
November 1930	15.2
April 1931	75.8
September 1931	16.9
February 1932	44.1
July 1932	237
January 1933	178
June 1933	245
November 1933	173
April 1934	241
September 1934	101
February 1935	151
July 1935	235
December 1935	100.0
May 1936	207
October 1936	92.7
March 1937	93.2
September 1937	145
February 1938	171
July 1938	231
December 1938	120
May 1939	233
October 1939	114
March 1940	189
August 1940	164
January 1941	129
June 1941	175
November 1941	28.6
May 1942	158
October 1942	74.6
March 1943	177
August 1943	227
January 1944	194
June 1944	240
November 1944	57.6
April 1945	148
September 1945	154
February 1946	142
July 1946	238
December 1946	139
June 1947	245
November 1947	181
April 1948	180
September 1948	166
February 1949	107
July 1949	229
December 1949	168
May 1950	129
October 1950	139
March 1951	134
August 1951	172
February 1952	143
July 1952	226
December 1952	60.5
May 1953	216
October 1953	126
March 1954	150
August 1954	213
January 1955	161
June 1955	238
November 1955	173
April 1956	121
October 1956	139
March 1957	187
August 1957	122
January 1958	81.8
June 1958	242
November 1958	71.5
April 1959	192
September 1959	113
February 1960	179
July 1960	212
December 1960	65.9
May 1961	214
November 1961	70.8
April 1962	204
September 1962	168
February 1963	193
July 1963	239
December 1963	71.8
May 1964	101
October 1964	133
March 1965	176
August 1965	130
January 1966	97.6
July 1966	207
December 1966	70.3
May 1967	198
October 1967	48.7
March 1968	221
August 1968	130
January 1969	153
June 1969	247
November 1969	49.6
April 1970	148
September 1970	67.9
February 1971	133
August 1971	209
January 1972	177
June 1972	210
November 1972	145
April 1973	180
September 1973	21.0
February 1974	153
July 1974	244
December 1974	157
May 1975	179
October 1975	157
April 1976	182
September 1976	151
February 1977	155
July 1977	202
December 1977	185
May 1978	231
October 1978	170
March 1979	187
August 1979	63.0
January 1980	58.4
June 1980	244
December 1980	108
May 1981	235
October 1981	67.0
March 1982	191
August 1982	231
January 1983	178
June 1983	243
November 1983	159
April 1984	217
September 1984	172
February 1985	108
July 1985	240
January 1986	153
June 1986	243
November 1986	97.3
April 1987	208
September 1987	83.0
February 1988	66.0
July 1988	231
December 1988	68.8
May 1989	224
October 1989	58.5
March 1990	172
September 1990	144
February 1991	176
July 1991	242
December 1991	70.0
May 1992	202
October 1992	27.6
March 1993	82.0
August 1993	194
January 1994	37.2
June 1994	166
November 1994	32.5
April 1995	196
October 1995	76.8
March 1996	203
August 1996	227
January 1997	141
June 1997	224
November 1997	172
April 1998	193
September 1998	129
February 1999	145
July 1999	242
December 1999	148
June 2000	243
November 2000	104
April 2001	143
September 2001	102
February 2002	112
July 2002	240
December 2002	83.9
May 2003	240
October 2003	63.1
March 2004	125
August 2004	215
February 2005	183
July 2005	236
December 2005	66.8
May 2006	228
October 2006	49.9
March 2007	216
August 2007	213
January 2008	125
June 2008	239
November 2008	89.9
April 2009	197
September 2009	143
March 2010	132
August 2010	233
January 2011	175
June 2011	240
November 2011	130
April 2012	201
September 2012	165
February 2013	168
July 2013	241
December 2013	137
May 2014	228
November 2014	76.0
April 2015	242
September 2015	120
February 2016	191
July 2016	235
December 2016	132
May 2017	228
October 2017	78.9
March 2018	219
August 2018	201
January 2019	91.4
July 2019	201
December 2019	88.7
May 2020	220
October 2020	87.4
March 2021	175
August 2021	204
January 2022	161
June 2022	239
November 2022	93.5
April 2023	163
September 2023	102
February 2024	128
August 2024	184
January 2025	46.8
June 2025	192
November 2025	52.5
April 2026	239
September 2026	144

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	130	198
Feb	153	209
Mar	171	225
Apr	184	239
May	211	238
Jun	233	231
Jul	232	226
Aug	213	204
Sep	141	144
Oct	70.0	26.1
Nov	82.7	52.5
Dec	107	129

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

1,217 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 1,217 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,217 would be longer than this page and unusable with a screen reader.
Period	Rimrock Lake (m)
1925.3333333333333	877
1925.75	857
1926.1666666666667	873
1926.5833333333333	868
1927	869
1927.4166666666667	889
1927.9166666666667	887
1928.3333333333333	890
1928.75	875
1929.1666666666667	876
1929.5833333333333	885
1930	859
1930.4166666666667	883
1930.8333333333333	855
1931.25	870
1931.6666666666667	854
1932.0833333333333	864
1932.5	891
1933	885
1933.4166666666667	892
1933.8333333333333	884
1934.25	892
1934.6666666666667	874
1935.0833333333333	881
1935.5	891
1935.9166666666667	874
1936.3333333333333	888
1936.75	873
1937.1666666666667	873
1937.6666666666667	881
1938.0833333333333	884
1938.5	891
1938.9166666666667	877
1939.3333333333333	891
1939.75	876
1940.1666666666667	886
1940.5833333333333	883
1941	879
1941.4166666666667	884
1941.8333333333333	860
1942.3333333333333	882
1942.75	870
1943.1666666666667	885
1943.5833333333333	890
1944	887
1944.4166666666667	891
1944.8333333333333	867
1945.25	881
1945.6666666666667	882
1946.0833333333333	880
1946.5	891
1946.9166666666667	880
1947.4166666666667	892
1947.8333333333333	885
1948.25	885
1948.6666666666667	883
1949.0833333333333	875
1949.5	890
1949.9166666666667	883
1950.3333333333333	879
1950.75	880
1951.1666666666667	879
1951.5833333333333	884
1952.0833333333333	880
1952.5	890
1952.9166666666667	867
1953.3333333333333	889
1953.75	878
1954.1666666666667	881
1954.5833333333333	889
1955	883
1955.4166666666667	891
1955.8333333333333	884
1956.25	877
1956.75	880
1957.1666666666667	886
1957.5833333333333	877
1958	871
1958.4166666666667	892
1958.8333333333333	869
1959.25	886
1959.6666666666667	876
1960.0833333333333	885
1960.5	888
1960.9166666666667	868
1961.3333333333333	889
1961.8333333333333	869
1962.25	888
1962.6666666666667	883
1963.0833333333333	886
1963.5	891
1963.9166666666667	869
1964.3333333333333	874
1964.75	879
1965.1666666666667	885
1965.5833333333333	879
1966	874
1966.5	888
1966.9166666666667	869
1967.3333333333333	887
1967.75	865
1968.1666666666667	889
1968.5833333333333	878
1969	882
1969.4166666666667	892
1969.8333333333333	865
1970.25	881
1970.6666666666667	869
1971.0833333333333	879
1971.5833333333333	888
1972	885
1972.4166666666667	888
1972.8333333333333	881
1973.25	885
1973.6666666666667	854
1974.0833333333333	882
1974.5	892
1974.9166666666667	882
1975.3333333333333	885
1975.75	882
1976.25	885
1976.6666666666667	881
1977.0833333333333	882
1977.5	887
1977.9166666666667	885
1978.3333333333333	891
1978.75	884
1979.1666666666667	886
1979.5833333333333	867
1980	867
1980.4166666666667	892
1980.9166666666667	875
1981.3333333333333	891
1981.75	869
1982.1666666666667	886
1982.5833333333333	891
1983	885
1983.4166666666667	892
1983.8333333333333	882
1984.25	889
1984.6666666666667	884
1985.0833333333333	876
1985.5	891
1986	882
1986.4166666666667	892
1986.8333333333333	874
1987.25	888
1987.6666666666667	871
1988.0833333333333	868
1988.5	891
1988.9166666666667	869
1989.3333333333333	890
1989.75	867
1990.1666666666667	884
1990.6666666666667	880
1991.0833333333333	884
1991.5	892
1991.9166666666667	869
1992.3333333333333	887
1992.75	859
1993.1666666666667	871
1993.5833333333333	887
1994	862
1994.4166666666667	883
1994.8333333333333	861
1995.25	887
1995.75	870
1996.1666666666667	888
1996.5833333333333	890
1997	880
1997.4166666666667	890
1997.8333333333333	884
1998.25	886
1998.6666666666667	878
1999.0833333333333	881
1999.5	892
1999.9166666666667	881
2000.4166666666667	892
2000.8333333333333	875
2001.25	880
2001.6666666666667	874
2002.0833333333333	876
2002.5	891
2002.9166666666667	872
2003.3333333333333	891
2003.75	868
2004.1666666666667	878
2004.5833333333333	889
2005.0833333333333	885
2005.5	891
2005.9166666666667	869
2006.3333333333333	890
2006.75	865
2007.1666666666667	889
2007.5833333333333	889
2008	878
2008.4166666666667	891
2008.8333333333333	873
2009.25	887
2009.6666666666667	880
2010.1666666666667	879
2010.5833333333333	891
2011	884
2011.4166666666667	891
2011.8333333333333	879
2012.25	887
2012.6666666666667	883
2013.0833333333333	884
2013.5	892
2013.9166666666667	880
2014.3333333333333	890
2014.8333333333333	870
2015.25	892
2015.6666666666667	877
2016.0833333333333	886
2016.5	891
2016.9166666666667	879
2017.3333333333333	890
2017.75	871
2018.1666666666667	889
2018.5833333333333	887
2019	873
2019.5	887
2019.9166666666667	872
2020.3333333333333	889
2020.75	872
2021.1666666666667	884
2021.5833333333333	888
2022	883
2022.4166666666667	891
2022.8333333333333	873
2023.25	883
2023.6666666666667	874
2024.0833333333333	878
2024.5833333333333	885
2025	864
2025.4166666666667	886
2025.8333333333333	865
2026.25	891
2026.6666666666667	880

Rate and persistence

+5.36 Mm³

Mean change per month over 12 months

12 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

Rimrock 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	1925–2026
Completeness	99.4% 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 1925 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-7196.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), Rimrock Lake reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usbr-7196/

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 Rimrock 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

1,217 monthly observations 1925–2026 Mm³

Spatially aggregatedHigh confidenceSeptember 2026

Source: USBR — Reservoir operations and Colorado River data, RISE catalogue item 132729. 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.