For over 90 years, Mackay Reservoir has provided much needed irrigation water to the Lost River Valley. Mining, livestock and agriculture provided a thriving economy in the valley. But the early days of the dam and reservoir can only be described as contentious leaving local residents wondering whether they had an asset or a liability.
Homesteaders were drawn to the Big Lost Valley in the early 1900s by the promise of cheap land and speculation that a 125-foot dam would be built to irrigate thousands of acres near Arco. These desert lands, located about 30 miles south of the Mackay farming area, had been set aside for irrigation and settlement under the Carey Land Act of 1894.
Although the water was badly needed, residents of Mackay also worried that the 125-foot dam might fail and fiercely protested its construction. After a prominent engineer condemned the dam’s design in 1910, plans were scaled back and a 65-foot dam was constructed followed by a canal system in the early 1920s.
Drought hit the area in the 1920s and early 30s. Water shortages were made worse by evaporative water loss from the reservoir and lengthy irrigation canals. By 1930 nobody was getting enough water, farms were abandoned, and property values were reduced by half.
Angry Mackay farmers, desperate to irrigate their lands, dynamited the dam’s controls, releasing all of the water in the reservoir back into the river. This supplied water locally to Mackay and stopped the irrigation through canals to farms near Arco. Resolution came in 1935 when local residents banded together and purchased the dam. They celebrated with the first annual Mackay Barbeque in 1935.
Mackay Reservoir Today
Since 1935, Mackay Reservoir has provided farmers and ranchers in the Big Lost River Valley with water for crops and livestock. When full, the 65-foot dam holds back 45,050 acre-feet of water, covering 1,341 acres. The Big Lost Irrigation District manages the dam and reservoir.
Today, Mackay Reservoir is also important for many outstanding natural resources and recreational uses. In the spring and fall, thousands of resident and migrating shorebirds and waterfowl flock to the reservoir for food, water and shelter. Boaters enjoy the reservoir in the summer for sailing, waterskiing and jet-skiing. Anglers also fish the reservoir year-round looking for the elusive giant fish or simply to pass a pleasant afternoon.
An acre-foot is the amount of water that covers one acre of land to a depth of one foot. That’s a little more than 325,000 gallons, or 1.2 million liters. When it’s full, Mackay Reservoir can hold about 14.6 billion gallons, or about 55.5 billion liters of water!
One of the oldest cemeteries in the Lost River Valley, Battleground Cemetery, is located just north of here on a hillside overlooking what is now Mackay Reservoir. Its first occupant is thought to be Captain Jesse McCaleb, for whom the mountain directly in front of you is named.
The story goes that in 1878 a freight wagon full of merchandise left Blackfoot for central Idaho. Near Mackay, the teamsters were joined by McCaleb and six men sent from Challis as an escort. On August 11, between 150 and 300 Bannock Indians attacked the convoy near the present day site of the dam.
Reportedly out-manned and outgunned, the convoy with 14 men held out for two days, suffering one casualty: Captain McCaleb. According to one account, McCaleb “stuck his bald head up once too often and was killed instantly by a single rifle shot.” His body was later disinterred and re-located to Salmon.