Arrowrock Dam: a dream cast in concrete

I had the privilege of touring Arrowrock Dam Sept. 9, and as I descended hundreds of stairs inside the dam, my steps took me not only far below the water’s surface, but back in time 100 years. In 1915 as World War I raged in Europe and Babe Ruth hit his first home run, the tallest dam in the world was rising on the Boise River.  

The first major project of the U.S. Reclamation Service, Arrowrock Dam was a dream cast in concrete, a manifestation of President Roosevelt’s determination to take waters that “now run to waste” and save them for irrigation. 

All last night I could hear splashing and slurring in the creek which flows rather placidly near my camp and this morning I was astonished to see it packed with fish. They actually jam the river as they fight their way up the stream.
— Jules DeFoe

The completion of Arrowrock Dam marked America’s entry into large-scale, irrigated agriculture, what author Steven Solomon calls “one of history’s most momentous innovations.” In his book, “Water,” Solomon links the rise of irrigation to the birth of civilization. Irrigation in ancient Sumeria and Egypt was designed and controlled by temple priests, and Solomon describes the U.S. Reclamation of the 20th century as “a modern democratic version of the ancient priestly elites.”

As our tour group assembled in the chill and dimly lit depths of the dam, I gazed at concrete that was poured when Manifest Destiny dominated the western psyche. Arrowrock Dam worked perfectly to save water for irrigation, and its completion ushered in what is today a billion-dollar agricultural industry. Roger Batt of the Treasure Valley Water Users Association reports that producers grow about 80 different crops in the Treasure Valley, including 40 species of seeds that are shipped to more than 120 countries. Our guide, Maintenance Supervisor Michael Anselme, conveyed enthusiasm for the dam, which continues to provide irrigation water to help mankind feed itself.

Other changes came to the Treasure Valley and the Boise River when the gates closed and Arrowrock Reservoir began to fill.  Arguably the most permanent change to the river was the loss of the salmon and steelhead that had plied the waters for millennia. The diversion tunnel used during construction from 1911 to 1915 and the completed dam totally blocked migrating salmon. 

Jules DeFoe, a trapper for the Northwest Fur Company, made an entry in his diary on June 29, 1789 while he was camped on the South Fork of the Boise River. 

“All last night I could hear splashing and slurring in the creek which flows rather placidly near my camp and this morning I was astonished to see it packed with fish,” he wrote. “They actually jam the river as they fight their way up the stream.” 

In 1834 another traveler, Townsend, wrote: “This is a beautiful stream, about 100 yards in width, clear as crystal, and, in some parts, probably 20 feet deep. It is literally crowded with salmon, which are springing from the water almost constantly.” 

Fish must have been in the Boise River when Barber Mill Dam was built near the present location of Idaho Shakespeare Festival in 1906 because the dam included a fish ladder.  The same goes for Reclamation’s Diversion Dam which was built in 1908 near the present location of the Hwy 21 bridge. Other forces were evidently dominant when Arrowrock Dam was built. Employees of Barber Lumber Company stated that 1916 was the last year in which spring chinook were observed at the fish ladder at Barber Mill Dam.

I breathed in fresh air after climbing the stairs inside the dam and returning outside. Anselme increased the flow of water jetting out the dam for us to enjoy, the mighty Boise River obstructed by a huge wall of concrete and made to flow by the turn of a dial. No one present when the ribbon was cut for Arrowrock Dam in 1915 could have foreseen how profoundly the dam would affect the Boise River.  

Now it’s our turn to make decisions. State and federal officials are considering raising Arrowrock Dam up to 74 feet, inundating more of the free-flowing Boise River and further impairing downstream flows for questionable benefit. In the past 100 years, we’ve learned that healthy rivers provide irreplaceable benefits. We’ve invested millions of dollars to improve water quality, build a world-class Greenbelt, create a trout fishery in downtown Boise, and secure public access because we love the Boise River. Let’s remember all the river does for us as we debate raising Arrowrock Dam.