Rimrock Lake — storage

Storage now, against this reservoir's own record

204.38 Mm³

Stored, August 2026

54th

Percentile among 102 Augs on record

-3.8%

Against the Aug 1991–2020 average

+22.4%

Change over the 12 months to 2026-08

Storage in August 2026 was around the middle of the Aug record, ranked against 102 other Augs held for this reservoir.

Storage, 1925–2026

Monthly mean storage

1,216 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 1,216 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,216 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
August 1937	188
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
April 1942	136
September 1942	91.5
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
May 1947	246
October 1947	146
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
January 1952	137
June 1952	244
November 1952	60.9
May 1953	216
October 1953	126
March 1954	150
August 1954	213
January 1955	161
June 1955	238
November 1955	173
April 1956	121
September 1956	162
February 1957	166
July 1957	198
December 1957	63.0
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
October 1961	57.9
March 1962	167
August 1962	222
January 1963	159
July 1963	239
December 1963	71.8
May 1964	101
October 1964	133
March 1965	176
August 1965	130
January 1966	97.6
June 1966	216
November 1966	46.3
April 1967	163
September 1967	94.3
February 1968	185
August 1968	130
January 1969	153
June 1969	247
November 1969	49.6
April 1970	148
September 1970	67.9
February 1971	133
July 1971	246
December 1971	166
May 1972	106
October 1972	133
March 1973	197
September 1973	21.0
February 1974	153
July 1974	244
December 1974	157
May 1975	179
October 1975	157
March 1976	187
August 1976	209
January 1977	141
June 1977	213
November 1977	83.1
April 1978	207
October 1978	170
March 1979	187
August 1979	63.0
January 1980	58.4
June 1980	244
November 1980	69.5
April 1981	241
September 1981	119
February 1982	165
July 1982	241
December 1982	175
May 1983	203
November 1983	159
April 1984	217
September 1984	172
February 1985	108
July 1985	240
December 1985	145
May 1986	199
October 1986	91.7
March 1987	172
August 1987	154
January 1988	50.8
June 1988	236
December 1988	68.8
May 1989	224
October 1989	58.5
March 1990	172
August 1990	218
January 1991	162
June 1991	244
November 1991	46.8
April 1992	168
September 1992	76.8
February 1993	69.5
July 1993	220
January 1994	37.2
June 1994	166
November 1994	32.5
April 1995	196
September 1995	146
February 1996	212
July 1996	244
December 1996	100
May 1997	172
October 1997	144
March 1998	178
August 1998	207
February 1999	145
July 1999	242
December 1999	148
May 2000	241
October 2000	104
March 2001	132
August 2001	166
January 2002	90.1
June 2002	240
November 2002	72.8
April 2003	226
September 2003	149
March 2004	125
August 2004	215
January 2005	150
June 2005	243
November 2005	55.4
April 2006	178
September 2006	133
February 2007	190
July 2007	241
December 2007	108
May 2008	161
October 2008	75.6
April 2009	197
September 2009	143
February 2010	119
July 2010	243
December 2010	139
May 2011	216
October 2011	122
March 2012	199
August 2012	236
January 2013	157
June 2013	244
November 2013	113
May 2014	228
October 2014	54.7
March 2015	244
August 2015	195
January 2016	154
June 2016	242
November 2016	113
April 2017	211
September 2017	136
February 2018	210
July 2018	231
December 2018	77.4
June 2019	199
November 2019	79.0
April 2020	188
September 2020	147
February 2021	162
July 2021	235
December 2021	139
May 2022	217
October 2022	87.0
March 2023	153
August 2023	177
January 2024	97.2
July 2024	213
December 2024	33.1
May 2025	168
October 2025	26.1
March 2026	225
August 2026	204

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	79.6
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

1,216 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 1,216 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 1,216 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
1937.5833333333333	886
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
1942.25	879
1942.6666666666667	873
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
1947.3333333333333	892
1947.75	881
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	880
1952.4166666666667	892
1952.8333333333333	867
1953.3333333333333	889
1953.75	878
1954.1666666666667	881
1954.5833333333333	889
1955	883
1955.4166666666667	891
1955.8333333333333	884
1956.25	877
1956.6666666666667	883
1957.0833333333333	883
1957.5	887
1957.9166666666667	868
1958.4166666666667	892
1958.8333333333333	869
1959.25	886
1959.6666666666667	876
1960.0833333333333	885
1960.5	888
1960.9166666666667	868
1961.3333333333333	889
1961.75	867
1962.1666666666667	883
1962.5833333333333	890
1963	882
1963.5	891
1963.9166666666667	869
1964.3333333333333	874
1964.75	879
1965.1666666666667	885
1965.5833333333333	879
1966	874
1966.4166666666667	889
1966.8333333333333	864
1967.25	883
1967.6666666666667	873
1968.0833333333333	885
1968.5833333333333	878
1969	882
1969.4166666666667	892
1969.8333333333333	865
1970.25	881
1970.6666666666667	869
1971.0833333333333	879
1971.5	892
1971.9166666666667	883
1972.3333333333333	875
1972.75	879
1973.1666666666667	887
1973.6666666666667	854
1974.0833333333333	882
1974.5	892
1974.9166666666667	882
1975.3333333333333	885
1975.75	882
1976.1666666666667	886
1976.5833333333333	888
1977	880
1977.4166666666667	889
1977.8333333333333	871
1978.25	888
1978.75	884
1979.1666666666667	886
1979.5833333333333	867
1980	867
1980.4166666666667	892
1980.8333333333333	869
1981.25	892
1981.6666666666667	877
1982.0833333333333	883
1982.5	892
1982.9166666666667	884
1983.3333333333333	888
1983.8333333333333	882
1984.25	889
1984.6666666666667	884
1985.0833333333333	876
1985.5	891
1985.9166666666667	881
1986.3333333333333	887
1986.75	873
1987.1666666666667	884
1987.5833333333333	882
1988	865
1988.4166666666667	891
1988.9166666666667	869
1989.3333333333333	890
1989.75	867
1990.1666666666667	884
1990.5833333333333	889
1991	883
1991.4166666666667	892
1991.8333333333333	864
1992.25	883
1992.6666666666667	870
1993.0833333333333	869
1993.5	889
1994	862
1994.4166666666667	883
1994.8333333333333	861
1995.25	887
1995.6666666666667	880
1996.0833333333333	888
1996.5	892
1996.9166666666667	874
1997.3333333333333	884
1997.75	880
1998.1666666666667	885
1998.5833333333333	888
1999.0833333333333	881
1999.5	892
1999.9166666666667	881
2000.3333333333333	892
2000.75	875
2001.1666666666667	879
2001.5833333333333	883
2002	873
2002.4166666666667	891
2002.8333333333333	870
2003.25	890
2003.6666666666667	881
2004.1666666666667	878
2004.5833333333333	889
2005	881
2005.4166666666667	892
2005.8333333333333	866
2006.25	885
2006.6666666666667	879
2007.0833333333333	886
2007.5	892
2007.9166666666667	875
2008.3333333333333	882
2008.75	870
2009.25	887
2009.6666666666667	880
2010.0833333333333	877
2010.5	892
2010.9166666666667	880
2011.3333333333333	889
2011.75	878
2012.1666666666667	887
2012.5833333333333	891
2013	882
2013.4166666666667	892
2013.8333333333333	876
2014.3333333333333	890
2014.75	866
2015.1666666666667	892
2015.5833333333333	887
2016	882
2016.4166666666667	892
2016.8333333333333	876
2017.25	888
2017.6666666666667	879
2018.0833333333333	888
2018.5	891
2018.9166666666667	870
2019.4166666666667	887
2019.8333333333333	871
2020.25	886
2020.6666666666667	881
2021.0833333333333	883
2021.5	891
2021.9166666666667	880
2022.3333333333333	889
2022.75	872
2023.1666666666667	882
2023.5833333333333	885
2024	874
2024.5	889
2024.9166666666667	861
2025.3333333333333	884
2025.75	859
2026.1666666666667	890
2026.5833333333333	888

Rate and persistence

+3.12 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	99.3% 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	2026-09-01
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 2026-09-02, 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

1,216 monthly observations 1925–2026 Mm³

Spatially aggregatedHigh confidenceAugust 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 September 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.