Reclamation Reservoir Operations Dataset

222,763

Observations

273

Series

Subjects

1905–2026

Period covered

What this looks like

One real series from the dataset, and real rows from the head of its published extract. Neither is a mock-up: the rows below are the same rows, unchanged, that are in the file you would download.

Reservoir stored volume at Kachess Lake

The longest single series this dataset holds — 1,451 monthly values, one of 273. Drawn from 600 of them, evenly spaced across the record. The dataset is not this chart.

Drawn to show the shape and resolution of what the dataset contains, not to make a point about Kachess Lake. Gaps are breaks, never interpolated.

View the data behind this chart

240 of 600 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 600 would be longer than this page and unusable with a screen reader.
Period	Kachess Lake (Mm³)
1905.75	7.85
1906.3333333333333	23.7
1906.75	9.17
1907.3333333333333	16.9
1907.75	3.53
1908.3333333333333	17.5
1908.75	2.28
1909.4166666666667	18.4
1909.75	2.05
1910.4166666666667	12.8
1910.8333333333333	11.4
1911.4166666666667	18.9
1911.8333333333333	0
1912.4166666666667	136
1912.8333333333333	76.6
1913.4166666666667	86.3
1913.8333333333333	63.5
1914.4166666666667	146
1914.8333333333333	34.4
1915.4166666666667	117
1915.8333333333333	35.5
1916.4166666666667	229
1916.8333333333333	157
1917.4166666666667	260
1917.8333333333333	114
1918.5	261
1918.8333333333333	145
1919.5	275
1919.8333333333333	143
1920.5	285
1920.9166666666667	161
1921.5	283
1921.9166666666667	191
1922.5	246
1922.9166666666667	50.8
1923.5	266
1923.9166666666667	117
1924.5	195
1924.9166666666667	74.4
1925.5	284
1925.9166666666667	140
1926.5	162
1926.9166666666667	73.3
1927.5	262
1927.9166666666667	204
1928.5833333333333	196
1928.9166666666667	168
1929.5833333333333	204
1929.9166666666667	177
1930.5833333333333	111
1931	69.4
1931.5833333333333	80.5
1932	63.7
1932.5833333333333	216
1933	216
1933.5833333333333	239
1934	195
1934.5833333333333	199
1935	190
1935.5833333333333	132
1936	128
1936.5833333333333	130
1937	109
1937.5833333333333	163
1938	184
1938.6666666666667	182
1939	191
1939.6666666666667	135
1940.0833333333333	173
1940.6666666666667	138
1941.0833333333333	157
1941.6666666666667	94.0
1942.0833333333333	150
1942.6666666666667	97.2
1943.0833333333333	134
1943.6666666666667	224
1944.0833333333333	244
1944.6666666666667	84.6
1945.0833333333333	135
1945.6666666666667	162
1946.3333333333333	268
1946.6666666666667	184
1947.3333333333333	288
1947.75	181
1948.3333333333333	267
1948.75	206
1949.3333333333333	264
1949.75	124
1950.3333333333333	234
1950.75	168
1951.3333333333333	273
1951.75	161
1952.3333333333333	280
1952.75	113
1953.3333333333333	266
1953.75	175
1954.3333333333333	254
1954.75	206
1955.3333333333333	256
1955.75	196
1956.4166666666667	290
1956.75	183
1957.4166666666667	287
1957.8333333333333	100
1958.4166666666667	266
1958.8333333333333	164
1959.4166666666667	296
1959.8333333333333	254
1960.4166666666667	297
1960.8333333333333	180
1961.4166666666667	294
1961.8333333333333	165
1962.4166666666667	298
1962.8333333333333	174
1963.4166666666667	285
1963.8333333333333	123
1964.4166666666667	291
1964.8333333333333	202
1965.5	267
1965.8333333333333	174
1966.5	259
1966.8333333333333	158
1967.5	279
1967.9166666666667	218
1968.5	250
1968.9166666666667	210
1969.5	270
1969.9166666666667	200
1970.5	273
1970.9166666666667	181
1971.5	295
1971.9166666666667	186
1972.5	292
1972.9166666666667	240
1973.5	163
1973.9166666666667	62.8
1974.5	292
1974.9166666666667	125
1975.5833333333333	271
1975.9166666666667	262
1976.5833333333333	291
1977	227
1977.5833333333333	210
1978	227
1978.5833333333333	247
1979	217
1979.5833333333333	112
1980	79.8
1980.5833333333333	170
1981	215
1981.5833333333333	238
1982	167
1982.5833333333333	240
1983	233
1983.5833333333333	246
1984	210
1984.5833333333333	239
1985	182
1985.6666666666667	92.6
1986	126
1986.6666666666667	39.2
1987.25	131
1987.6666666666667	35.5
1988.25	112
1988.6666666666667	44.7
1989.25	167
1989.6666666666667	131
1990.25	241
1990.6666666666667	224
1991.25	273
1991.6666666666667	204
1992.25	245
1992.6666666666667	35.5
1993.3333333333333	158
1993.6666666666667	28.6
1994.3333333333333	127
1994.75	25.1
1995.3333333333333	217
1995.75	100
1996.3333333333333	268
1996.75	41.6
1997.3333333333333	263
1997.75	158
1998.3333333333333	290
1998.75	104
1999.3333333333333	246
1999.75	164
2000.3333333333333	286
2000.75	140
2001.3333333333333	200
2001.75	25.8
2002.4166666666667	274
2002.75	144
2003.4166666666667	290
2003.75	63.5
2004.4166666666667	200
2004.8333333333333	76.0
2005.4166666666667	193
2005.8333333333333	44.4
2006.4166666666667	203
2006.8333333333333	130
2007.4166666666667	294
2007.8333333333333	140
2008.4166666666667	286
2008.8333333333333	189
2009.4166666666667	294
2009.8333333333333	140
2010.4166666666667	273
2010.8333333333333	161
2011.4166666666667	292
2011.8333333333333	169
2012.5	294
2012.8333333333333	189
2013.5	292
2013.8333333333333	172
2014.5	289
2014.9166666666667	198
2015.5	213
2015.9166666666667	123
2016.5	272
2016.9166666666667	148
2017.5	284
2017.9166666666667	171
2018.5	279
2018.9166666666667	149
2019.5	242
2019.9166666666667	71.7
2020.5	265
2020.9166666666667	156
2021.5	281
2021.9166666666667	195
2022.5833333333333	273
2022.9166666666667	151
2023.5833333333333	153
2024	63.0
2024.5833333333333	131
2025	68.3
2025.5833333333333	109
2026	149
2026.5833333333333	191

Sample rows

12 of 223,788 rows Taken from the start of observations-reservoir-us-bureau-reclamation.csv. These are sample rows, not the dataset.

Sample rows from the Reclamation Reservoir Operations Dataset extract
`metric_id`	`subject_id`	`subject_kind`	`value`	`censored`	`censor_operator`	`censor_threshold`	`censor_limit`	`censor_reported`	`unit`	`period_start`	`period_end`	`period_kind`	`basis`	`confidence`	`source_id`	`source_ref`	`qualifier`	`superseded`	`retrieved`
reservoir-inflow	reservoir-usbr-1533	geography	10.356394	—	—	—	—	—	m³/s	1968-12-01	1968-12-31	month	aggregated	high	us-bureau-reclamation	RISE catalogue item 4279	—	—	2026-09-01
reservoir-inflow	reservoir-usbr-1533	geography	10.330504	—	—	—	—	—	m³/s	1969-01-01	1969-01-31	month	aggregated	high	us-bureau-reclamation	RISE catalogue item 4279	—	—	2026-09-01
reservoir-inflow	reservoir-usbr-1533	geography	9.929379	—	—	—	—	—	m³/s	1969-02-01	1969-02-28	month	aggregated	high	us-bureau-reclamation	RISE catalogue item 4279	—	—	2026-09-01
reservoir-inflow	reservoir-usbr-1533	geography	10.045239	—	—	—	—	—	m³/s	1969-03-01	1969-03-31	month	aggregated	high	us-bureau-reclamation	RISE catalogue item 4279	—	—	2026-09-01
reservoir-inflow	reservoir-usbr-1533	geography	53.309286	—	—	—	—	—	m³/s	1969-04-01	1969-04-30	month	aggregated	high	us-bureau-reclamation	RISE catalogue item 4279	—	—	2026-09-01
reservoir-inflow	reservoir-usbr-1533	geography	107.90624	—	—	—	—	—	m³/s	1969-05-01	1969-05-31	month	aggregated	high	us-bureau-reclamation	RISE catalogue item 4279	—	—	2026-09-01
reservoir-inflow	reservoir-usbr-1533	geography	86.217907	—	—	—	—	—	m³/s	1969-06-01	1969-06-30	month	aggregated	high	us-bureau-reclamation	RISE catalogue item 4279	—	—	2026-09-01
reservoir-inflow	reservoir-usbr-1533	geography	63.450709	—	—	—	—	—	m³/s	1969-07-01	1969-07-31	month	aggregated	high	us-bureau-reclamation	RISE catalogue item 4279	—	—	2026-09-01
reservoir-inflow	reservoir-usbr-1533	geography	30.846601	—	—	—	—	—	m³/s	1969-08-01	1969-08-31	month	aggregated	high	us-bureau-reclamation	RISE catalogue item 4279	—	—	2026-09-01
reservoir-inflow	reservoir-usbr-1533	geography	20.833301	—	—	—	—	—	m³/s	1969-09-01	1969-09-30	month	aggregated	high	us-bureau-reclamation	RISE catalogue item 4279	—	—	2026-09-01
reservoir-inflow	reservoir-usbr-1533	geography	32.332484	—	—	—	—	—	m³/s	1969-10-01	1969-10-31	month	aggregated	high	us-bureau-reclamation	RISE catalogue item 4279	—	—	2026-09-01
reservoir-inflow	reservoir-usbr-1533	geography	14.981364	—	—	—	—	—	m³/s	1969-11-01	1969-11-30	month	aggregated	high	us-bureau-reclamation	RISE catalogue item 4279	—	—	2026-09-01

Download these rows as CSV — the same twelve, with the column header, for testing a loader before committing to the full file.

Methodology

Aggregated by Hydrionis from the daily values published by the Bureau of Reclamation. Storage is published in acre-feet and converted to millions of cubic metres using the exact definition of the acre-foot; elevations are converted from feet, and inflow and release from cubic feet per second. A month is published only where at least twenty days of record exist. Reservoirs need twenty years of record, and at most twenty-five are taken from each Reclamation region. Inflow and release are taken only where the publisher states them as a rate: the same quantities are also published as daily volumes in acre-feet, which are a different measurement, and those series are left alone rather than divided by a day length the publisher did not state.

What this dataset cannot tell you

Read before relying on these figures

No percentage full is published, because no capacity is. The Bureau publishes what is in each reservoir but not what it holds when full — of the 782 quantities in its catalogue, the only ones named capacity are the generating capacity of the powerplants — so the denominator does not exist and is not invented.
Water levels are elevations against each operator’s own datum, and those datums are not a common surface: Lake Mead is published against a local datum established at Hoover Dam in 1912. Levels are comparable within one reservoir’s record and never between reservoirs.
A level is not a proxy for storage. The same one-metre fall releases far more water from a full reservoir, where the surface is wide, than from a nearly empty one.
Inflow is usually inferred from the change in storage and what was released rather than gauged, so it carries the errors of both and can be negative where the balance does not close.
A release is an operating decision rather than a catchment response, and is not the natural flow of the river below the dam.
Reservoir storage is managed as well as observed: a drawdown may record a flood-control rule curve or a scheduled release rather than a shortage.

Coverage

Subjects	Bureau of Reclamation reservoirs with 20+ years of record, capped at twenty-five per Reclamation region — 91 held
Period	1905–2026
Units	Mm³, m, m³/s
Update cadence	Monthly
Identifier	`us-reservoir-operations` v1.0.0

Fields

Data dictionary →

Every metric this dataset carries, with the unit it is stored in and the geography level it is reported at. Full definitions are in the data dictionary.

Identifier	Field	Unit	Reported at
`reservoir-storage-volume`	Reservoir stored volume Volume of water held in a reservoir at a given time.	Mm³	reservoir-site
`reservoir-water-level`	Reservoir water level Elevation of the water surface in a reservoir, above the datum the operator uses.	m	reservoir-site
`reservoir-inflow`	Reservoir inflow Rate at which water enters a reservoir from its catchment.	m³/s	reservoir-site
`reservoir-release`	Reservoir release Rate at which water is released from a reservoir to the river below it.	m³/s	reservoir-site

Rights and access

Licence position

Open. Derivative use true; redistribution true; commercial reuse true.

Applies to material authored by US federal agencies. Third-party material carried within a federal product may be separately protected.

Permitted uses

Public display
Derived analysis
API delivery
Bulk download
Commercial use

Available to: Public, Developer, Research, Professional, Enterprise. These follow from the rights of the contributing publishers, not from a Hydrionis pricing decision — no access tier can widen what a publisher withheld.

Contributing sources

United States Bureau of Reclamation — Reservoir operations and Colorado River data (US Government work — public domain)

Attribution and citation

Cite and reuse →

Two different obligations, deliberately kept apart. One is a condition of somebody else's licence; the other is a request Hydrionis has no standing to enforce.

Suggested citation for Hydrionis

Hydrionis (2026), Reclamation Reservoir Operations Dataset, version 1.0.0, accessed 2026-09-02, hydrionis.com/data/datasets/us-reservoir-operations/

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: Reclamation Reservoir Operations Dataset 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.

Changelog

Version 1.0.0 — 2026-09-01

First release. Adds the operated western reservoirs, and with them reservoir water level, inflow and release as measures Hydrionis holds for the first time.

Additions

Monthly storage, water level, inflow and release for federal reservoirs of the western United States.

Use this data

Download reservoir observations from USBR (223,788 rows) (CSV)
Machine-readable JSON /api/v1/datasets/us-reservoir-operations.json
How to cite this, and who you must credit
How these figures were produced
Request this at a different scale, format or geography

Every bulk extract ships with a companion metadata file carrying this dataset’s version, its sources, their licences, the attribution you are required to give and the suggested citation — so the terms travel with the file rather than staying on this page.

About this data

The fields a professional user needs to judge whether this is fit for a particular purpose. Deliberately not a score.

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	Mixed across the series — the basis is recorded on every individual value.
Period held	1905–2026
Known gaps	No percentage full is published, because no capacity is. The Bureau publishes what is in each reservoir but not what it holds when full — of the 782 quantities in its catalogue, the only ones named capacity are the generating capacity of the powerplants — so the denominator does not exist and is not invented. Water levels are elevations against each operator’s own datum, and those datums are not a common surface: Lake Mead is published against a local datum established at Hoover Dam in 1912. Levels are comparable within one reservoir’s record and never between reservoirs. A level is not a proxy for storage. The same one-metre fall releases far more water from a full reservoir, where the surface is wide, than from a nearly empty one.
Continuity	Version 1.0.0, released 2026-09-01. 1 recorded version; breaking changes and corrections are listed in the changelog above.
Last read from the publisher	2026-09-01 · publisher updates monthly
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