Idaho reservoir storage

Reservoir contents on 30 September each year, from Reclamation's Hydromet daily archive.

Historical data

Source: U.S. Bureau of Reclamation, Pacific Northwest Hydromet: Reservoir Storage and Active Capacity. Retrieved September 8, 2026.

Data table (116 rows)

Period	Jackson Lake at Dam on Snake River near Moran, WY (acre-feet)	Cascade Dam and Lake Cascade at Cascade, Idaho (acre-feet)	Anderson Ranch Dam and Reservoir (acre-feet)	Lake Lowell at Lower Embankment near Caldwell, ID (acre-feet)	Palisades Reservoir near Irwin, ID (acre-feet)	Arrowrock Dam and Reservoir (acre-feet)	Henrys Lake Dam and Lake on Henrys Fork nr. Lake, ID (acre-feet)	Deadwood Dam, Idaho (acre-feet)
1910	112,900	n/a	n/a	n/a	n/a	n/a	n/a	n/a
1911	74,160	n/a	n/a	n/a	n/a	n/a	n/a	n/a
1912	111,970	n/a	n/a	n/a	n/a	n/a	n/a	n/a
1913	71,820	n/a	n/a	n/a	n/a	n/a	n/a	n/a
1914	117,180	n/a	n/a	n/a	n/a	n/a	n/a	n/a
1915	58,960	n/a	n/a	n/a	n/a	n/a	n/a	n/a
1916	264,550	n/a	n/a	n/a	n/a	n/a	n/a	n/a
1917	341,440	n/a	n/a	n/a	n/a	n/a	n/a	n/a
1918	167,130	n/a	n/a	n/a	n/a	23,780	n/a	n/a
1919	340	n/a	n/a	n/a	n/a	600	n/a	n/a
1920	142,920	n/a	n/a	n/a	n/a	0	n/a	n/a
1921	170,250	n/a	n/a	n/a	n/a	23,950	n/a	n/a
1922	255,650	n/a	n/a	n/a	n/a	640	n/a	n/a
1923	145,200	n/a	n/a	n/a	n/a	14,480	n/a	n/a
1924	2,410	n/a	n/a	n/a	n/a	910	n/a	n/a
1925	390,020	n/a	n/a	n/a	n/a	15,700	n/a	n/a
1926	1,380	n/a	n/a	n/a	n/a	2,030	n/a	n/a
1927	519,100	n/a	n/a	n/a	n/a	35,770	n/a	n/a
1928	590,030	n/a	n/a	n/a	n/a	3,400	n/a	n/a
1929	395,140	n/a	n/a	n/a	n/a	5,400	n/a	n/a
1930	246,140	n/a	n/a	n/a	n/a	17,460	n/a	n/a
1931	4,990	n/a	n/a	n/a	n/a	700	n/a	2,500
1932	376,070	n/a	n/a	n/a	n/a	22,820	n/a	66,800
1933	204,140	n/a	n/a	n/a	n/a	15,340	n/a	56,430
1934	5,500	n/a	n/a	n/a	n/a	8,990	n/a	4,150
1935	113,270	n/a	n/a	n/a	n/a	11,070	n/a	13,930
1936	360,660	n/a	n/a	n/a	n/a	9,200	n/a	58,520
1937	232,020	n/a	n/a	n/a	n/a	12,610	n/a	46,450
1938	398,710	n/a	n/a	n/a	n/a	38,600	n/a	123,740
1939	313,170	n/a	n/a	n/a	n/a	15,620	n/a	56,240
1940	166,350	n/a	n/a	n/a	n/a	44,200	n/a	85,320
1941	226,110	n/a	n/a	n/a	n/a	39,090	n/a	138,790
1942	321,330	n/a	n/a	n/a	n/a	18,460	n/a	91,400
1943	650,340	n/a	n/a	n/a	n/a	64,680	n/a	127,000
1944	300,570	n/a	n/a	n/a	n/a	10,940	n/a	54,290
1945	568,030	n/a	n/a	n/a	n/a	20,480	n/a	79,210
1946	402,740	n/a	−39,060	n/a	n/a	75,520	n/a	88,920
1947	463,990	n/a	−39,250	n/a	n/a	89,100	n/a	53,300
1948	234,260	−50,000	−29,380	n/a	n/a	73,000	n/a	69,740
1949	273,140	−41,420	−28,670	n/a	n/a	31,250	n/a	89,650
1950	570,390	30,970	225,900	n/a	n/a	14,990	n/a	130,380
1951	622,680	15,930	303,600	53,883.6	n/a	41,070	n/a	960
1952	281,730	37,200	266,100	50,650	n/a	34,810	n/a	65,600
1953	232,430	164,300	273,400	52,010	n/a	35,890	n/a	68,900
1954	316,600	161,700	242,200	66,212.7	n/a	15,820	n/a	48,720
1955	192,820	134,500	232,200	38,826.3	n/a	21,100	n/a	52,960
1956	369,650	310,300	361,200	66,278.9	n/a	9,870	n/a	43,480
1957	615,760	374,300	325,000	56,879.7	422,700	38,140	n/a	65,920
1958	497,320	362,600	272,300	88,545.1	535,000	53,200	n/a	73,860
1959	551,320	419,200	347,000	21,778.5	449,000	30,800	n/a	49,920
1960	374,960	344,200	267,900	79,724.2	42,000	5,300	n/a	53,930
1961	3,270	307,000	92,900	53,128.8	294,000	680	n/a	37,010
1962	525,370	387,300	365,100	96,500.3	770,000	6,090	n/a	58,860
1963	611,930	409,300	365,890	101,064.6	696,000	31,810	n/a	63,650
1964	588,370	423,000	308,650	111,699.5	849,000	31,600	n/a	59,240
1965	631,570	518,900	378,400	129,931.3	1,161,000	167,150	n/a	81,370
1966	516,780	247,600	237,100	26,528.9	271,000	37,580	n/a	61,380
1967	558,840	388,700	336,600	100,754.6	828,000	3,820	n/a	58,570
1968	585,530	341,300	235,900	121,500.2	1,095,000	4,440	n/a	50,600
1969	569,700	354,300	343,500	110,094.5	649,000	4,460	n/a	60,130
1970	573,900	449,500	358,200	86,497.2	919,000	35,160	n/a	62,710
1971	598,300	491,100	420,800	86,716.8	1,067,000	61,860	83,500	68,430
1972	584,800	405,800	389,200	47,419.4	1,049,000	35,450	82,700	70,330
1973	607,400	236,300	262,230	34,567.1	628,680	19,310	74,900	0
1974	586,700	488,400	351,500	56,141.2	1,019,000	57,090	82,000	67,300
1975	576,990	458,300	348,400	56,264.3	1,069,640	50,120	76,800	65,608.6
1976	563,600	472,500	335,380	85,474.2	1,120,230	18,440	81,300	66,770.7
1977	227,260	166,700	57,900	15,375.5	31,970	760	60,200	29,114.9
1978	534,700	523,410	336,720	112,983.1	1,132,180	54,740	87,700	62,200
1979	497,780	254,960	227,520	66,146.5	634,030	41,650	81,800	38,410
1980	514,680	452,120	284,700	100,364.8	820,850	159,060	81,700	82,920
1981	481,418.9	342,851.4	323,500	74,462	294,613.1	36,705.6	71,600	73,821.1
1982	514,221	504,894.1	373,325.8	115,311.3	1,177,315.5	135,520	87,400	71,000
1983	485,780.2	513,014.2	419,383.8	108,650.2	1,150,161.4	43,341.1	88,457.2	69,626.3
1984	276,696	409,525	319,653.8	97,783	1,198,522.5	176,802.7	82,542	85,424.3
1985	146,546.4	366,023.1	251,134.2	88,837.9	725,597.6	61,376.3	80,231.8	61,865.4
1986	93,000	398,223.8	328,808.5	95,895.8	1,147,000	163,844.5	73,600	69,156.4
1987	60,200	321,775.2	102,526.5	48,068.8	384,000	0	74,300	51,649.3
1988	57,400	324,965	104,221.3	60,152.3	165,674	1,088	59,097.7	44,423.2
1989	582,680	397,824.2	234,291.1	74,187.8	599,777.8	6,645.1	79,235.3	70,291.9
1990	574,161.6	470,134.3	156,444.7	28,211.7	5,925	39,800.5	76,261.8	68,478.8
1991	641,192.7	402,988.6	55,095.5	48,068.8	522,523.5	4,834	75,368.2	60,474.1
1992	131,211.9	317,115.6	1,085.6	11,333	133,208	31,328.2	50,470.3	40,630.4
1993	637,096.1	413,969.3	323,955.5	33,652.3	927,792	83,249.2	85,565.3	96,658.9
1994	353,424.4	280,721.4	32,106.6	13,065	44,245.4	11,046	67,104.4	51,906.4
1995	646,474.9	570,766	367,581	90,666.2	988,974.1	40,960.1	88,724.6	125,824.5
1996	643,352.6	507,966.9	362,880	98,069.9	888,913.9	47,878.5	84,072.2	124,453.1
1997	668,256.1	506,544	376,844.9	105,225.2	1,077,745	41,880.3	88,523.9	120,393
1998	582,911.6	464,937.3	341,823.4	89,629.8	940,903.5	76,244.2	84,718.2	119,860.8
1999	651,545.8	461,096.4	325,786.1	90,337.6	904,436.3	68,278.5	85,891.6	109,355.4
2000	646,474.9	343,974.8	251,625.7	82,424	253,873.2	51,336.2	79,158.3	91,499.1
2001	126,298.3	253,548.5	55,263.5	27,695	104,727	67,782.7	48,499.8	51,120.9
2002	224,880.4	372,657.3	114,158.9	49,971.7	82,050.3	53,530.9	63,019.8	54,197.4
2003	134,798	361,727	252,104	103,871.7	75,331.1	1,530	62,408.1	79,209.3
2004	79,040	400,377	188,884.1	107,937	135,261	65,717	59,335.9	69,278.5
2005	345,344.6	364,385	201,614	79,453	364,692.9	50,043	82,412	66,538.4
2006	637,096.1	381,256	266,819	66,176	546,028.8	75,498	83,687	91,025.4
2007	269,780.9	337,049	116,366	64,963	23,281.1	66,462	71,672.1	56,331.7
2008	641,673.9	384,883	229,565	68,556	450,439.5	57,526	81,700.2	74,909
2009	653,733.6	371,280	264,978	84,408	701,527.2	72,879	82,731.7	87,426
2010	650,576	365,363	278,778	76,542	500,029.5	119,370	82,412	92,256
2011	641,427.4	424,309	328,655	82,469	1,063,588	102,772	84,783	87,964
2012	579,599.2	354,642	224,925	81,094	150,566.6	77,861	82,542	82,789
2013	156,131.4	338,943	99,737	32,385	77,936.9	62,807	66,675.8	62,471
2014	640,946.2	354,642	209,267	67,911	530,687.4	78,202	85,826.7	93,946
2015	556,963.3	299,083	208,884	97,095	340,240.1	66,040	74,168.7	68,143
2016	444,172.3	327,660	213,710	93,034	96,923.6	78,187	75,304.6	85,572
2017	650,091	420,483	299,277	98,415	1,059,668	125,333	82,152	113,272
2018	645,512	367,333	239,878	83,505	631,198	71,106	77,949	81,977
2019	571,332	374,656	281,189	103,092	835,024	58,628	82,152	86,914
2020	646,710	375,658	245,710	103,693	599,671	78,218	78,711	75,974
2021	134,042	328,225	142,214	76,205	79,969	43,720	77,257	56,481
2022	140,080	369,898	311,573	80,614	140,767	49,461	71,858	71,446
2023	558,838	380,452	346,491	111,165	672,704	100,740	80,485	89,137
2024	650,813	370,487	279,592	101,076	517,180	72,596	79,223	63,733
2025	545,226	362,815	242,010	108,318	96,813	77,336	76,509	72,868

Storage by reservoir

Reservoir contents on 30 September each year, from Reclamation's Hydromet daily archive.

Source: U.S. Bureau of Reclamation, Pacific Northwest Hydromet: Reservoir Storage and Active Capacity. Data period 2025. Retrieved September 8, 2026.

Data table (21 rows)

Reservoir	2025 (acre feet)
Jackson Lake at Dam on Snake River near Moran, WY	545,226
Cascade Dam and Lake Cascade at Cascade, Idaho	362,815
Anderson Ranch Dam and Reservoir	242,010
Lake Lowell at Lower Embankment near Caldwell, ID	108,318
Palisades Reservoir near Irwin, ID	96,813
Arrowrock Dam and Reservoir	77,336
Henrys Lake Dam and Lake on Henrys Fork nr. Lake, ID	76,509
Deadwood Dam, Idaho	72,868
Minidoka Dam and Lake Walcott, ID	72,707
Lucky Peak Lake near Boise, ID	58,688
American Falls Reservoir at American Falls, ID	50,924
Ririe Dam and Lake near Ririe, ID	48,429
Island Park Dam and Reservoir, ID	45,588
Black Canyon Dam and Reservoir near Emmett, ID	29,477
Payette Lake at McCall, Idaho	18,700
Grassy Lake near Moran, WY	9,623
Little Wood Dam and Reservoir near Carey, ID	2,789
Lake Waha near Lewiston, ID	932.4
Reservoir A Near Lewiston Orchards, ID	780
Soldiers Meadow Reservoir	627
Mann Creek Dam and Reservoir nr Weiser, ID	302

Source

Organization: U.S. Bureau of Reclamation
Dataset: Pacific Northwest Hydromet: Reservoir Storage and Active Capacity
Geography: Idaho (statewide; two of the twenty-one reservoirs, Jackson Lake and Grassy Lake, are physically sited in Wyoming)
Time coverage: 1910-2025 (storage, varies by station); 2013 (capacity)
Update frequency: Annual (storage, one value per water year); irregular (capacity, revised only after events such as a sedimentation survey)
Published: not stated
Retrieved: September 8, 2026
Original file: https://www.usbr.gov/pn-bin/daily.pl
Methodology: https://www.usbr.gov/pn/hydromet/station.js
License: Public domain. U.S. federal government work.
Our copy: usbr-reservoirs, built by scripts/fetch-usbr-reservoirs.py

Caveats

Storage is read on 30 September each year, the approximate close of Idaho's irrigation season, so a low figure can reflect scheduled seasonal drawdown for delivery rather than drought; it is one dated reading per reservoir per year, not a live level.
Reclamation labels this Hydromet data provisional and subject to revision.
Active capacity figures come from Reclamation Pacific Northwest Region's Monthly Reservoir Status Report; the only edition served at that URL is dated May 2013, and Reclamation has not republished a newer one there. Active capacity changes only rarely (for example after a sedimentation survey), so the 2013 figure is still Reclamation's current published number for these reservoirs absent a newer edition.
That report did not carry an active-capacity figure for four of the twenty-one reservoirs (Black Canyon, Henrys Lake, Payette Lake, and Lake Waha); water.reservoir_capacity has no observation for those four, while water.reservoir_storage covers all twenty-one.
Jackson Lake and Grassy Lake are sited in Wyoming; they are included because Reclamation administers them as upstream Snake River System storage released for delivery to Idaho irrigators, the same reasoning the sibling lpag repo's reservoir puller already applied to Jackson Lake.
Magic Reservoir, on the Big Wood River, is often grouped with these systems but is a State of Idaho project, not a Bureau of Reclamation one; it carries no code in Reclamation's Hydromet network and is not included here.
Storage figures are stored to one decimal acre-foot as Reclamation's daily archive publishes them; capacity figures are converted from the report's thousand-acre-foot column to acre-feet.
publisherUpdated is omitted: the storage series is updated after each 30 September while the capacity table was last republished in May 2013, so the two metrics in this dataset do not share one release date.

Data

Download the full dataset behind this page as CSV or JSON, or browse the data catalog. Cite this page as Understand Idaho, “Idaho reservoir storage”, https://understandidaho.com/water/reservoirs/, retrieved on the date you read it.