Reclamation Reservoir Operations Dataset

236,997

Observations

298

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 — 1,452 monthly values, one of 298. 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
1919.9166666666667	148
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
1926.5833333333333	66.7
1926.9166666666667	73.3
1927.5833333333333	222
1927.9166666666667	204
1928.5833333333333	196
1929	174
1929.5833333333333	204
1930	185
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
1935.6666666666667	117
1936	128
1936.6666666666667	124
1937	109
1937.6666666666667	137
1938.0833333333333	196
1938.6666666666667	182
1939.0833333333333	207
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
1944.75	66.5
1945.0833333333333	135
1945.75	165
1946.3333333333333	268
1946.75	157
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
1952.4166666666667	288
1952.75	113
1953.4166666666667	296
1953.8333333333333	185
1954.4166666666667	294
1954.8333333333333	215
1955.4166666666667	293
1955.8333333333333	235
1956.4166666666667	290
1956.8333333333333	198
1957.4166666666667	287
1957.8333333333333	100
1958.4166666666667	266
1958.8333333333333	164
1959.4166666666667	296
1959.8333333333333	254
1960.4166666666667	297
1960.8333333333333	180
1961.5	271
1961.8333333333333	165
1962.5	275
1962.9166666666667	208
1963.5	238
1963.9166666666667	139
1964.5	298
1964.9166666666667	227
1965.5	267
1965.9166666666667	185
1966.5	259
1966.9166666666667	183
1967.5	279
1967.9166666666667	218
1968.5	250
1968.9166666666667	210
1969.5	270
1969.9166666666667	200
1970.5833333333333	218
1970.9166666666667	181
1971.5833333333333	261
1972	187
1972.5833333333333	295
1973	241
1973.5833333333333	85.0
1974	88.6
1974.5833333333333	216
1975	157
1975.5833333333333	271
1976	254
1976.5833333333333	291
1977	227
1977.5833333333333	210
1978	227
1978.5833333333333	247
1979	217
1979.6666666666667	51.6
1980	79.8
1980.6666666666667	134
1981.0833333333333	234
1981.6666666666667	165
1982.0833333333333	201
1982.6666666666667	195
1983.0833333333333	250
1983.6666666666667	197
1984.0833333333333	242
1984.6666666666667	184
1985.0833333333333	187
1985.6666666666667	92.6
1986.0833333333333	139
1986.6666666666667	39.2
1987.3333333333333	186
1987.6666666666667	35.5
1988.3333333333333	161
1988.75	34.0
1989.3333333333333	219
1989.75	85.6
1990.3333333333333	279
1990.75	161
1991.3333333333333	287
1991.75	123
1992.3333333333333	270
1992.75	30.6
1993.3333333333333	158
1993.75	24.5
1994.3333333333333	127
1994.75	25.1
1995.4166666666667	257
1995.75	100
1996.4166666666667	216
1996.75	41.6
1997.4166666666667	284
1997.8333333333333	176
1998.4166666666667	294
1998.8333333333333	106
1999.4166666666667	288
1999.8333333333333	172
2000.4166666666667	293
2000.8333333333333	135
2001.4166666666667	193
2001.8333333333333	45.3
2002.4166666666667	274
2002.8333333333333	136
2003.4166666666667	290
2003.8333333333333	79.9
2004.5	186
2004.8333333333333	76.0
2005.5	169
2005.8333333333333	44.4
2006.5	219
2006.9166666666667	155
2007.5	289
2007.9166666666667	159
2008.5	293
2008.9166666666667	209
2009.5	289
2009.9166666666667	156
2010.5	281
2010.9166666666667	178
2011.5	294
2011.9166666666667	173
2012.5	294
2012.9166666666667	208
2013.5833333333333	266
2013.9166666666667	193
2014.5833333333333	271
2015	232
2015.5833333333333	162
2016	141
2016.5833333333333	236
2017	153
2017.5833333333333	257
2018	189
2018.5833333333333	246
2019	170
2019.5833333333333	178
2020	104
2020.5833333333333	236
2021	178
2021.5833333333333	262
2022	212
2022.6666666666667	210
2023	162
2023.6666666666667	81.0
2024.0833333333333	78.6
2024.6666666666667	79.0
2025.0833333333333	75.0
2025.6666666666667	53.0
2026.0833333333333	170
2026.6666666666667	124

Sample rows

12 of 238,385 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	—	—	2026-10-01
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	—	—	2026-10-01
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	—	—	2026-10-01
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	—	—	2026-10-01
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	—	—	2026-10-01
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	—	—	2026-10-01
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	—	—	2026-10-01
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	—	—	2026-10-01
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	—	—	2026-10-01
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	—	—	2026-10-01
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	—	—	2026-10-01
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	—	—	2026-10-01

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 — 96 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 2026-10-05, 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 (238,385 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	2026-10-01 · 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