Arrowrock Reservoir, Idaho, USA
One in a string of three major reservoirs built to irrigate the parched Boise Valley, Arrowrock Reservoir has contributed to water recreation in southwestern Idaho for nearly a hundred years. Arrowrock Dam was the tallest concrete arch structure in the world at 348 feet when completed in 1915, a title it held until 1924. Located at the confluence of the main channel and the south fork of the Boise River, the dam incorporated a series of new innovations into its preparatory work and construction. When completely filled, the reservoir stretched 18 miles up the canyon and covered 3,141 acres with water. When the dam was refurbished in 1937, another five feet in height were added to the dam. The ‘Y’-shaped reservoir extends back along both the south fork and the main fork of the Boise River. Although no absolute depths are recorded for the reservoir, depth is at least 260 feet at the base of the dam. Because the walls of the canyon are steep, actual depths within the reservoir are likely deeper in spots.
Arrowrock Reservoir is not heavily visited, despite being only a 30-minute drive from Boise. Steep canyon walls make access to much of the 60-mile shoreline difficult. Neighboring Lucky Peak Reservoir just a few miles downstream is equipped with more organized recreational opportunities in Lucky Peak State Park, so many visitors go there instead. This lack of visitors keeps Arrowrock an ideal place to engage nature in an active manner. Many of the day-use sites located at Arrowrock Reservoir are only accessible by water, and only one boat launch site exists. Water levels may fall as much as 200 feet when there is heavy water withdrawal for irrigation, but provisions are made for this expected variation at the ramp site. For boaters lucky enough to find it, Arrowrock Reservoir offers excellent water for power boating, water skiing, wake-boarding and sailing. Some swimming is offered at the campsites, most of which are spread along the reservoir and rather primitive. The reservoir lies within the Boise National Forest and is managed by the U.S. Forest Service.
Fishing is one of the most popular activities at Arrowrock Reservoir. Rainbow trout, kokanee, yellow perch, whitefish, and bull trout are all present, but bull trout must be returned to the water as they are a protected species. Some ice fishing can be engaged in away from the main stream of the river. Both the Arrowrock Recreation Area and Boise National Forest are available for hiking, wildlife viewing and hunting in certain areas in season. A number of hiking trails exist in the area, although most are steep and usually termed ‘difficult’. The National Forest provides habitat for bear, deer, mountain goats, quail, pheasant, turkey, grouse, rabbit and a number of other mammals. Mule deer use the area as a part of their annual migration paths. Because of the difficult terrain, the area around Arrowrock Reservoir remains isolated and natural.
Building the dam in the early 1900s was a monumental feat: the process required that the downstream Diversion Dam near Boise be retrofitted with hydroelectric turbines to provide electrical power to the dam site. A railroad was actually constructed to transport materials and workers to the construction location. The dam workforce was treated to such luxuries as electricity, dormitory housing, hot water and a hospital, although they complained about low pay. Provision for future hydroelectric power generation was built into the dam from the beginning, but turbines were not installed until 2010. Because the need for water storage continues to grow, the United States Army Corps of Engineers recently completed a study of the feasibility of adding another 74 feet to the height of the dam – a massive undertaking. The Boise River below the dam forms the farthest reaches of the Lucky Peak Reservoir. Changes to the Arrowrock Dam may well mean changes will occur at Lucky Peak Reservoir also. Environmental concerns will doubtlessly be given heavy weight in any future decision, so it is not likely that any construction will begin in the near future.
Being in such close proximity to the Boise metropolitan area means that the wilderness areas surrounding Arrowrock Reservoir are actually accessible to a large number of people. Named after the river that flows through the city, origins of the city’s name appear to come from the designation of French-Canadian fur trappers in the 1820s who called the river, “La Riviere Boisee”, meaning wooded river. By 1863, the US Army had established a fort in the area to protect parts of the Oregon Trail and silver and gold mining claims in the area – all activities bringing in a large number of settlers. Now a thoroughly modern city and the capital of Idaho, Boise is home to a large number of nature lovers who wish to escape the city and enjoy a day on the water or in the mountains. One of the sport’s hottest new races, the Ironman Boise 70.3 triathlon takes place at Lucky Peak Reservoir for the swimming portion and introduces a new group of athletes to the area every year.
Visitors can enjoy both the best of what Boise has to offer in terms of cultural activities and spend time in solitude on the water within the same afternoon. If visitors choose not to camp at either Arrowrock Reservoir or Lucky Peak State Park next door, a number of small motel lodgings can be found around the area. Rental properties and lodges exist nearby where visitors can enjoy both Arrowrock Reservoir in summer and winter sports during the colder months. Favored activities include cross-country skiing and snowmobiling, with downhill ski venues within a few minutes’ drive. Real estate with mountain or lake views are available in the area, although not at Arrowrock Reservoir. The reservoir and the adjacent recreation area are the ideal spots for cleansing the mind of the clutter of modern living. So come to Arrowrock Reservoir and give your soul a much-needed break. There’s nothing quite like it!
Things to do at Arrowrock Reservoir
- Vacation Rentals
- Ice Fishing
- Water Skiing
- Downhill Skiing
- Cross-Country Skiing
- Wildlife Viewing
- State Park
- National Forest
Fish species found at Arrowrock Reservoir
- Bull Trout
- Kokanee Salmon
- Rainbow Trout
- Yellow Perch
Arrowrock Reservoir Photo Gallery
Arrowrock Reservoir Statistics & Helpful Links
Water Level Control: US Bureau of Reclamation
Surface Area: 3,141 acres
Shoreline Length: 60 miles
Normal Elevation (Full Pond): 3,260 feet
Water Volume: 272,200 acre-feet
Completion Year: 1937
Drainage Area: 2,210 sq. miles
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