Reservoir report

Idaho reservoirs & dams

Every documented dam and reservoir in Idaho — with normal storage capacity, dam height, max discharge, hazard classification, and drainage area. Sourced from USACE NID and state water-resource agencies.

Dams in Idaho

408

Total storage

17,409,890ac·ft

High-hazard dams

102

Updated

May 25

Open the Idaho reservoir layer on the map Every dam and reservoir filtered to Idaho on the interactive map.

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May

2026

Reservoir report

Idaho has numerous reservoirs and dams that provide irrigation, hydropower, and recreational opportunities. Major reservoirs include Lucky Peak, Anderson Ranch, and American Falls. These reservoirs are fed by streams and rivers such as the Boise River, Snake River, and Portneuf River. The hydrology of the area is heavily influenced by snowfall in the surrounding mountains, particularly the Sawtooth and Rocky Mountains. Snowpack levels are closely monitored as they impact streamflow and reservoir levels. In recent years, drought conditions have led to lower snowpack levels and decreased reservoir levels. Record low levels have been seen in several reservoirs during drought years. Seasonal trends show higher reservoir levels during the spring and early summer due to snowmelt, with levels decreasing through the fall and winter. Overall, reservoirs and dams play a significant role in Idaho's water management and the state's economy.

Idaho at a glance

Storage, hazard, and history

How the Idaho dam inventory breaks down -- aggregate stats computed across every documented dam in the state.

Hazard classification

High102
Significant143
Low162
Unknown1

USACE downstream-consequence rating, not failure likelihood.

Notable dams

Tallest Thompson Mtis 789 ft
Oldest Johnson 1860
Total storage All Idaho dams 17,409,890 ac·ft

Built by decade

Most U.S. dams were built mid-20th century during the federal water-development era.

Full inventory

Idaho dams & reservoirs

Every documented dam in Idaho. Sortable by any column; quickly filterable by name. Numeric columns heat-mapped from light to deep based on value. Tap any dam for the full report.

Name	Year built	Normal storage	Dam height	Max discharge	Hazard	Drainage area
Saint John	1918	630	43	76	High	11
Deep Creek Upper	1906	512	36	51	Significant	4
Samaria No 1 Lower	1934	559	35	144	Significant	7
Samaria No 2 Upper	1947	700	46	130	Significant	7
Deep Creek	1952	5,537	91	835	High	30
Daniels	1967	8,700	96	9,500	High	107
Curlew Valley	1911	3,800	41	2,524	Significant	253
Henrys Lake	1923	58,700	25	1,175	High	93
Blue Creek Upper	1920	67	18	91	Low	6
Little Valley	1897	1,322	23	1	Low	5
Enders	·	151	13	15	Low	3
Twenty Four Mile	1928	700	27	499	Significant	8
Wiregrass	1943	86	17	49	Low	6
Paul	1911	50	28	70	Low	2
Wilson Lake	1909	4,600	31	1,278	Significant	135
Cow Creek	1915	400	34	897	Low	5
Mormon	1908	19,280	27	1,250	High	61
Campbell	1913	550	16	300	Low	6
Francis	1914	330	33	220	Significant	4
Mchan	1918	345	21	157	Low	5
Thorn Creek Dam	·	640	24	60	Low	11
Dog Creek	1958	550	26	240	Significant	6
Sublett	1914	2,400	48	385	High	46
Lake Cleveland	1914	59	7	0	Low	1
Dewey	1913	225	30	687	Significant	99
Crowther	1948	959	90	106	High	1
Hawkins	1870	880	35	418	Significant	27
Trail Creek	1937	67	23	1,060	High	63
Pioneer	1910	844	15	3,080	Significant	162
Magic Dam	1910	191,500	128	97,000	High	1,600
Magic Spillway	1910	191,500	50	100,000	High	1,600
Little Wood River	1941	30,000	129	9,200	High	286
Bray Lake	1915	2,693	36	0	Significant	2
Deep Creek No 1	1911	88	18	165	Low	81
Salmon Falls	1911	230,650	224	0	High	1,610
Cedar Creek	1920	30,000	90	235	High	128
Mcmullen	1948	350	25	370	Significant	31
Williams	1952	1,025	53	3,400	Significant	3
Pacific Land Co	1965	368	27	86	Low	18
Swan Falls	1901	7,425	88	105,112	High	41,900
Twin Falls	1935	955	16	60,000	Low	19,000
Twin Falls Intake Dam	1935	955	34	0	Low	19,000
Lower Salmon	1949	10,900	110	72,000	High	1,965
Bliss	1950	8,415	140	100,000	High	35,800
C J Strike	1952	247,000	115	140,000	High	40,800
Hells Canyon	1967	170,000	323	300,000	High	73,300
Brownlee	1958	1,470,000	395	307,300	High	72,800
Oxbow	1961	58,200	145	300,000	High	73,000
Sunset Palisades	1973	41	41	296	Significant	0
Grace Main	1908	900	51	12,500	Significant	4,070
Grace Dike	·	900	10	·	Significant	4,070
Soda	1925	15,200	103	45,150	High	3,970
Hammond	1933	645	33	100	Significant	2
Montpelier Creek	1971	4,050	82	2,944	High	28
Soda Creek Main Dam	1967	2,500	36	187	High	10
Casperson	1958	110	22	71	Low	3
Five Mile Erosion Contr	1952	250	44	274	Low	11
Van Orden	1961	64	23	154	Low	53
Oneida Main	1920	10,880	114	74,270	High	4,456
Oneida Embankment	1921	10,880	60	·	High	4,445
Johnson	1860	396	28	0	Significant	1
Condie	1948	2,292	41	0	Significant	1
Lamont	1948	2,040	68	0	High	0
Nash	1952	94	21	164	Low	4
Weston	1929	2,066	42	230	High	14
Winder	1958	2,000	57	0	Significant	1
Twin Lakes South	1920	14,000	36	0	High	2
Foster	1962	2,969	70	0	High	1
Tingey	1955	132	25	13	Low	5
Alder	1909	960	21	0	Low	2
Diamond A	1931	3,926	29	0	Low	31
Snow Creek North	1957	320	13	200	Low	5
Tindall	1951	130	13	24	Low	1
Foland	1916	135	11	0	Low	0
Hardisty	1914	789	31	550	Significant	2
Slack	1916	5,000	20	92	Low	58
Juniper Creek	1923	260	16	54	Low	1
Hardisty Wilson West	1918	174	18	70	Low	0
Hagberry	1925	110	23	143	Low	0
Sommerville	1926	550	29	84	Low	1
Louisa Creek	1931	175	41	30	Low	8
Spencer	1939	160	23	650	Significant	23
Nouque	1967	100	21	1,950	Low	127
Foreman	1929	200	21	6	Significant	2
Tyson West	1967	150	42	0	Low	0
Walker	1954	490	14	0	Significant	4
Long Tom	1906	3,600	60	450	Significant	27
Little Canyon	1919	575	30	57	Significant	2
Little Camas	1912	18,800	55	580	Significant	40
Louie Lake	1928	361	18	5	Low	1
Payette Lake Upper	1953	2,400	15	1,070	Significant	42
Sage Hen	1939	5,210	46	1,670	Significant	11
Knox Meadow	1941	1,073	19	63	Significant	1
Davis	1942	1,200	34	137	Significant	·
Koskella	1947	74	24	55	Low	0
Poro	1947	59	22	178	Low	4
Gatfield No 2	1951	70	20	66	Significant	0
Smalley	1952	113	35	94	Low	1
Jussila Bow	1949	175	23	128	Significant	1
Jug Creek Upper	1946	1,132	32	375	Significant	3
Holbrook	1955	71	17	160	Low	6
Hughes	1957	141	43	267	Significant	3
Horsethief	1967	4,900	53	310	Significant	8
Hollenbeak	1972	159	29	550	Low	1
Surmeier	1978	26	32	35	Significant	0
Blackhawk Lake	1968	1,630	45	178	Significant	4
Haw Creek	1970	100	27	265	Significant	5
Hornet Creek Upper North	1913	265	21	67	Significant	1
Little (North Crane Creek Dam)	1895	224	28	830	Significant	5
Crane Creek Main Dam	1912	56,800	64	4,330	High	242
C Ben Ross	1937	8,550	61	189	High	6
Bar D	1950	227	26	260	Significant	138
Challis Lake	1951	189	19	80	Low	1
Mosquito Flat	1950	793	58	4,360	Significant	16
Shiner Upper	1968	250	29	39	Significant	5
Billy Creek	1916	75	16	32	Low	1
Gorley Creek	1913	115	19	15	Low	1
Hancock	1931	198	29	291	Significant	6
Elk River	1951	463	22	2,917	Low	42
Thompson No 1 Main Dam	1967	54	17	3	Significant	0
Winchester	1910	1,425	40	1,100	High	13
Soldiers Meadow	1921	2,370	69	7,040	High	4
Spring Valley	1962	721	47	190	High	3
Chilco	1907	340	17	240	Significant	2
Twin Lakes	2005	9,090	14	770	Significant	51
Mcarthur	1967	1,085	15	1,970	High	28
Moyie	1949	540	62	21,000	High	755
Andreasen Lower	1960	100	33	12	Significant	1
Heil No 1	1974	480	24	52	Low	4
Stoneridge	1969	256	28	685	Significant	35
Murtaugh Lake	1905	7,720	42	0	High	238
Upper Diversion Dam #1	1982	800	23	60,000	Low	9,800
Upper Diversion Dam #2	1982	800	33	15,000	Low	9,800
Upper Dike	1982	800	12	0	Low	9,800
Fife	·	54	13	6	Low	0
Sheep Creek	1951	213	18	74	Low	12
Oxford	1920	315	21	0	Low	1
Glendale	1930	5,727	73	0	High	15
Sheridan	1873	2,105	22	0	Significant	7
Ashton	1917	9,800	65	46,100	High	1,040
Portneuf	1912	20,504	55	462	High	97
Mackay	1918	45,000	75	7,000	High	788
Lamb-Weston	1974	120	20	50	Low	1
Fish Creek	1923	5,515	92	720	High	75
Taylor Lower	1965	160	18	110	Significant	1
Cedar Creek Holding	1966	200	24	162	Low	7
Salmon Falls Creek	1956	60	13	2,800	Low	2,170
Grasmere North Dam	1936	658	22	55	Significant	1
Strickland	1927	560	35	395	Low	95
Little Blue Creek	1914	2,100	37	258	Significant	30
Big Blue Creek	1910	2,100	34	670	Significant	66
Bybee	1987	7,970	60	4,280	Low	24
Lone Tree	1918	415	12	5	Low	2
Payne Creek	1930	570	33	200	Low	15
King Reservoir (West Dam)	1969	300	30	31	Significant	1
Hall	1945	450	33	350	Significant	14
Hot Springs No 2	1968	5,334	41	100	High	20
Equalizer	1937	2,300	25	·	High	·
Blackfoot	1911	350,000	35	15,450	High	581
Orchard	1902	2,035	43	1,500	Significant	51
Barber	1904	180	26	37,922	Low	2,700
Blacks Creek	1915	3,640	52	1,200	High	39
Beal No 3	1974	149	30	78	Significant	1
Jemima K	1974	2,650	71	260	Significant	4
Monroe	1916	272	36	170	Low	1
Jenkins Creek	1915	175	41	0	Low	1
Fairchild No. 1 (Upper)	1975	3,303	78	14	High	0
Courtright	1973	90	24	46	Low	0
Post Falls Middle Channel	1906	225,000	64	·	High	3,784
Post Falls North Channel	1906	225,000	31	34,740	High	3,784
Post Falls South Channel	1906	225,000	25	3,600	High	3,784
Post Falls Earth Dike	1990	225,000	16	0	High	3,784
Cabinet Gorge	1952	104,600	166	260,000	High	22,073
Milner Dam-Middle	1905	39,000	80	116,850	Significant	17,180
Milner S Embankment	1992	39,000	65	·	Significant	·
Upper Salmon Falls Dam	1937	600	23	48,000	Low	32,200
Welling No 2	1962	147	29	13	Low	1
Strong Arm No 2 (Lower)	1897	377	27	0	Significant	2
Strong Arm No 1 (Upper)	1887	1,713	39	360	High	30
Devil Creek	1969	4,464	84	3,410	High	15
Arcadia Lower	1912	882	23	78	Low	80
Arcadia Upper	1912	300	21	36	Low	69
Spring Creek	1918	200	17	10	Low	5
Oakley	1916	76,000	145	1,240	High	729
Deep Creek No 2	1911	1,500	42	200	Significant	80
Scrappy Creek	1927	437	20	650	Low	17
Squaw Creek	1968	1,140	61	770	High	11
Rock Creek	1965	1,184	37	2,050	Significant	54
Mountain Home	1884	5,468	48	0	High	37
Trail	1960	2,532	30	29	Significant	3
Trail Diversion	1962	63	28	1,200	Low	29
Shaw Twins Upper	1930	188	17	48	Low	0
Boulder Lake	1902	1,310	15	160	Significant	2
Little Payette Lake Main	1926	10,300	25	3,000	High	64
Payette Lake	1943	41,000	13	7,330	Significant	144
Granite Lake	1949	2,900	25	73	Significant	2
Herrick	1953	562	38	190	Significant	5
Corral Creek	1952	560	43	120	Significant	1
Little (Upper Bissel Creek Dam)	1963	1,228	37	282	Significant	1
Boulder Meadow	1968	490	35	757	Significant	4
Paddock Valley	1949	22,300	49	350	High	35
Hidden Lake	1970	375	26	120	Significant	1
Little Crane Creek	1908	500	33	2,150	Low	1
Barton	1915	685	52	0	Significant	1
Hornet Creek Lower	1913	150	26	45	Low	1
Lost Valley	1910	9,583	31	505	High	29
Mill Creek Lake	1928	210	19	53	Low	1
Goose Lake	1919	6,550	27	1,145	High	8
Twin Granite	1920	600	25	64	Low	1
Reservoir A	1906	3,300	61	·	High	1
Hayden Lake	1910	38,000	13	0	Low	64
Blanchard Creek	1910	240	19	108	Significant	34
China Hat	1925	125,000	24	0	Low	581
Box Lake	1935	476	13	141	Low	1
Island Park	1937	127,646	93	5,000	High	481
Island Park Dike	1937	127,646	12	·	High	·
Palisades	1957	1,401,000	270	48,500	High	5,208
American Falls	1927	1,671,300	87	87,000	High	13,580
Minidoka	1906	210,200	88	40,552	High	15,625
Minidoka South Dike	1906	210,200	21	·	High	15,625
Deer Flat Upper	1907	190,500	74	1,270	High	92
Deer Flat East Dike	1911	159,000	18	·	Low	92
Deer Flat Lower	1907	190,500	48	1,270	High	92
Deer Flat Middle Dike	1911	159,000	18	·	High	92
Deer Flat Middle	1911	63,000	14	0	High	75
Deer Flat Lower	1907	173,200	50	0	High	75
Anderson Ranch	1946	464,216	456	20,000	High	960
Arrowrock	1915	272,224	350	16,080	High	2,230
Boise River Diversion	1908	1,000	57	40,000	High	2,680
Black Canyon Diversion	1923	29,822	183	39,060	High	2,680
Cascade	1948	703,000	110	12,500	High	2,230
Deadwood	1931	162,000	143	11,300	High	111
Mann Creek	1966	12,952	148	3,885	High	56
Mountain View Dam	1969	5,500	30	·	Low	·
Dworshak Dam	1973	3,468,000	0	221,000	High	2,440
Lucky Peak Dam	1955	293,138	0	93,300	High	2,680
Galena No 2 Mtis	·	60	48	36	Significant	0
Osburn	·	519	71	0	High	0
Sunshine No 2	·	1,085	54	0	Significant	0
Simplot Effluent Irrigation Lagoon	1981	900	39	210	High	0
Moose Creek	1960	240	20	450	Low	11
Priest Lake	1979	76,100	12	4,400	Significant	572
Albeni Falls Dam	1955	1,153,000	0	420,000	High	24,200
Lodge Pond	1910	50	15	0	Significant	0
Warren Diversion	1924	100	19	908	Significant	56
Dry Creek Main	1976	1,859	68	·	High	3
Eld	1976	121	19	300	Low	4
Pitkin	1974	110	21	48	Significant	6
Sulphur Gulch	1976	50	23	56	Low	2
North Cove Creek	1975	94	26	440	Low	2
Tom J	1995	2,960	57	250	Significant	7
Brace	1921	250	25	0	Undetermined	0
Land	1976	90	15	0	Low	0
Scott Creek	1977	90	20	100	Significant	13
Craig	1978	68	18	129	Low	1
Shiner Lower	1973	50	18	123	Low	21
Boggeman	1963	35	24	820	Significant	35
Brundage	1936	7,330	63	360	High	6
Olson	1981	119	24	280	Low	3
Lower Diversion	1982	800	14	75,000	Low	9,800
Gardiner Lower	1935	66	21	16	Low	2
Ririe	1976	90,500	253	40,000	High	487
Current Creek	1977	800	49	480	Significant	3
Mikesell Upper	1945	80	16	0	Low	6
Cross Cut Diversion	1938	250	18	20,000	Low	1,752
Webster	1976	55	22	127	Low	9
Munsee	1977	90	23	28	Low	2
Pershall	1948	50	27	99	Low	1
Shoofly	1977	1,100	46	400	Low	9
Brown	1958	80	26	22	Low	1
Hulet	1976	4,290	99	1,040	High	57
Teapot Lower	1977	912	32	85	Significant	75
Teapot Upper	1977	424	28	40	Significant	74
Texas Basin	1979	6,340	121	6,280	High	52
Hubbard	1902	4,060	23	·	Low	3
Stewart Ranch	1965	50	15	43	Low	1
Conda Site Mtis (Simplot)	1979	1,700	45	0	Significant	0
Star No 6	1979	175	33	0	High	0
Lucky Friday No 3	1979	1,130	102	0	Significant	0
Summit	1941	99	13	60	Low	1
Josephine Creek	1983	185	24	780	Low	27
Brown	1979	99	21	180	Low	2
Bruce	1980	280	24	110	Significant	2
Rhead Ranch	1974	380	34	650	Low	41
Silver Lake	1915	700	13	130	Significant	29
Summit	1921	752	19	5	Low	9
Grasmere Middle Dam	1936	420	16	18	Low	1
Taylor Upper	1964	120	18	8	Significant	1
Hot Springs No 3	1984	553	28	250	Significant	23
Pine Lake	1974	65	17	86	Low	1
Soulen Main Dam	1935	630	18	0	Significant	2
Cinnabar	1975	173	26	274	Low	2
Kimberly Lake	1970	36	27	310	Significant	9
Bradshaw Detention Dam #4	1967	21	·	574	Low	10
Thompson Srd	1982	75	77	65	Significant	4
Nelson	1907	65	17	3	Low	0
Kiblen North	1969	23	26	8	Low	0
City Diversion	1982	400	30	75,000	Low	9,800
Idaho Falls Upper Diversion Dam No 1	1982	362	28	60,000	Low	9,050
Henrys Fork Ranch	1987	109	23	140	Low	4
Fairchild No 2 (Lower)	1988	108	24	80	Significant	1
Yanke	1988	65	29	38	Low	1
Egbert Dam	1982	70	15	87	Low	9
Smoky Canyon No 1	1983	2,500	80	0	Low	1
Indian Creek Pond	1990	97	28	1,356	Significant	22
Thompson Mtis	1982	895,000	789	0	High	3
Hulet No 2 Dam	1987	6,770	55	0	Significant	16
Smoky Canyon No 2	1992	20,455	108	0	Significant	9
Macks Creek	1993	469	58	780	Significant	12
Bradshaw Detention Dam #3	·	3	·	271	Low	2
South Fork Detention Dam	·	24	·	220	Low	4
Grouse Creek South	1994	6,428	300	0	Significant	1
Andreasen Upper	1957	40	29	0	Significant	1
Jacobs	1935	75	19	333	Low	12
Lehman Creek Upper	1925	54	22	21	Low	9
Grouse Creek Main Dam	1992	57	17	0	Low	0
Itafos Cooling Pond	1995	592	20	40	High	0
Itafos Tailings Pond #4	1985	12,168	71	0	Significant	0
Antelope Creek	1991	67	22	280	Significant	·
Elkington	1994	90	35	196	Low	5
Stanislaw Lake	1997	70	13	8	Significant	0
Cottonwood Creek Lower	1961	88	15	3,540	Significant	17
Crane Gulch Main Fork	1998	19	46	1,550	Significant	2
Crane Gulch East Dam	1998	28	60	1,900	Significant	2
Stewart Gulch Main Fork	1998	61	76	168	Significant	4
Beartrack Treatment Lagoon	1995	77	20	0	Low	0
Beartrack H2o Overflow Pond	1995	205	35	0	Low	0
Idc-Effluent Storage	1998	105	23	0	Significant	0
Aikman	1999	2,000	77	825	High	20
Lehman Creek Lower	1999	60	21	240	Low	11
J-Ditch Effluent Lagoon	2001	645	42	0	High	0
Grouse Creek North	1994	152	110	0	Significant	1
Courtright Dike	1973	90	12	46	Low	0
Deer Creek	2003	975	48	140	Significant	2
Nixon No 2	·	80	13	0	Low	1
Tyson North	1967	150	27	0	Low	0
Point Of Rock	2004	358	30	495	Significant	88
Dry Creek Dike	1976	1,484	34	0	Significant	3
Crane Creek Dike	1912	35,300	25	4,330	High	242
Grasmere East Dam	·	453	11	58	Significant	1
Grasmere South Dike	1909	110	11	0	Low	1
Hardisty Wilson East	1918	120	9	70	Low	0
Hornet Creek Upper South	1913	265	19	67	Significant	1
Jughandle Estates	1974	27	28	12	Significant	0
Little Payette Lake Dike	1926	3,550	11	3,000	Significant	64
Oneida Dike	1913	4,456	47	9,900	High	4,456
Snow Creek South	1957	280	11	200	Low	5
Soda Creek Dike	1967	827	16	·	Low	5
Soulen Auxiliary Dike	1935	240	7	0	Low	2
Twin Lakes North	1920	14,000	32	0	High	2
Walker Dike	1954	290	7	0	Low	4
Dry Creek Diversion	1976	77	35	·	Low	12
Gatfield No 1	1938	14	16	26	Significant	1
Cottonwood Creek Upper	1961	17	18	3,540	Significant	17
Cottonwood Creek Middle	1961	40	20	3,540	Significant	17
Hansen	1976	3	18	0	Significant	0
Thompson No 2	1970	15	19	1	Significant	0
Horseshoe	1967	20	·	185	Low	2
Spencer	1954	25	15	3	Significant	0
Gorley Creek Dike	1913	92	16	·	Low	1
Morrison	1959	66	17	11	Low	0
Rundell	1975	23	19	88	Significant	0
Idaho Falls Upper Powerhouse Dam No 2	1982	424	37	13,500	Low	9,050
J-Canal Reregulating	1994	25	19	150	Significant	1
King Reservoir South Dam	1969	300	33	31	Significant	1
Indian Creek Upper	1975	89	15	5	Low	5
Tom J Dike	1995	107	27	0	Significant	7
Hidden Springs Cell 3a	2007	81	43	·	Significant	0
Kiblen West	1969	16	23	8	Significant	0
Indian Creek	1930	19	19	140	Significant	10
Gimlet	1987	16	24	48	Significant	1
Rio Vista	1971	41	20	118	Significant	0
Flying Joseph Dam	2008	51	14	·	Low	373
Delamar Wmp-1	2009	376	42	·	Low	·
Simplot Decant Pond	2009	146	21	·	Low	0
Arrowhead Reservoir	1975	16	20	37	Significant	0
Haul Road Pond (Monsanto)	2009	70	30	·	Low	·
Soulen Family Dam	2009	66	22	160	Low	1
W-Drain	2008	99	17	·	Significant	·
Deyo	2011	550	35	267	Significant	2
Horseshoe Bend Diversion	1995	116	8	·	Low	2,230
Hulet No 2 Dike	1987	2,500	13	·	Low	16
Lucky Friday No 4	2010	624	132	·	High	0
Idaho Cobalt Wmp	2019	91	21	·	Low	·
Bird Pond	2010	62	17	·	Low	0
Blackfoot Bridge Wmp #1 & #2	2012	606	35	0	Significant	0
Springfeild Bird Haven	·	239	13	0	Low	0
Toponce Ditch Dam Lower	·	78	18	·	Low	·
Sirucek Reservoir	2003	143	17	·	Low	0
Kinyon Pond Dam	2014	225	13	·	Low	·
Galena Mill No 3 Lower	1979	130	64	0	Significant	0
Stewart Gulch North Fork	1997	8	38	440	Significant	1
Upper Bear Dam	1910	82	13	·	Low	·
Buffalo River	1936	50	10	500	Low	35
Avondale Lake	·	139	9	·	Significant	2
Seeley Lower	·	86	14	·	Low	·
Gem State	1988	5,000	40	140,000	High	4,650
Gem State Right Dike	1988	5,000	30	·	High	4,650
Gem State Left Dike	1988	5,000	30	·	High	4,650
Egin Canal Diversion	1903	500	7	50,000	Low	1,770
Ravenscroft Diversion	1983	100	10	8,800	Low	2,990
Upper Salmon Falls A-Plant Diversion Dam	1937	150	9	84,000	Low	32,200
Shoshone Falls Dam 1	1907	1,500	16	12,000	Low	19,500
Shoshone Falls Dam 2	1907	1,500	16	12,000	Low	19,500
Shoshone Falls Dam 3	1907	1,500	15	12,000	Low	19,500
Shoshone Falls Dam 4	1907	1,500	18	12,000	Low	19,500
Upper Salmon Falls B-Plant Forebay	1947	90	70	6,500	Low	32,200
Upper Salmon Falls A-Plant & Forebay	1937	26	85	6,000	Low	32,200

Reservoir FAQ

About Idaho dams & reservoirs

Where does the Idaho dam data come from?

The U.S. Army Corps of Engineers National Inventory of Dams (NID) plus state water-resource agencies. Snoflo joins these public records with live USGS streamgauge readings downstream where available. The NID is the canonical federal dam registry.

What does Hazard Potential mean?

USACE classifies every dam by what would happen if it failed: Low (no loss of life expected, minimal economic damage), Significant (no loss of life but economic, environmental, or lifeline damage), High (loss of life expected). It's a downstream-consequence rating, not a likelihood of failure.

What is Normal Storage in acre-feet?

The volume of water the reservoir holds at its normal operating level, measured in acre-feet. One acre-foot is about 325,851 gallons or 1,233 cubic meters — the amount needed to cover one acre to a depth of one foot.

Why are some Idaho dams missing storage or height data?

USACE NID records can have gaps for small or older dams that pre-date federal reporting requirements. Snoflo surfaces whatever the canonical record contains. If a dam you care about has incomplete data, contact the operating agency or USACE for updates.

Can I see live water levels?

Yes — tap any dam name to open its detail page, which pulls live storage data from USGS streamgauges or operating-agency feeds where available. Historical levels and seasonal averages are also shown.

Why does Idaho have so many dams?

The U.S. has over 90,000 dams — most built between 1930 and 1980 during the federal water-development era. Idaho's count reflects a combination of agricultural irrigation needs, flood control, hydropower, and recreation. The "Built by decade" chart above shows the timeline.