Ash Creek Images
Photographs of the West by Doug Gorsline
Spring Runoff at Bonneville Dam Creates a Dramatic Scene at the Spillways
For most of the year, most of the flow of the Columbia River is directed through the power generating electrical turbines at Bonneville Dam, but for a few months in the spring and early summer, there is far more water coming down the river than the generators can handle. At the peak of spring runoff, up to half the water in the river and sometimes more has to be directed over the spillways.
When the spillway gates are open at Bonneville Dam, water thunders over the dam and churns into wild waves and currents downstream. Both sides of the river below the dam are heavily rip-rapped with large basalt boulders to prevent erosion. A little of this rip-rap is visible at the lower right corner. The structure at the far right of the photo is the entrance to one of several fish ladders at the dam.
The generating capacity of Bonneville Dam is over a million kilowatts of electricity from two powerhouses. While this power can fairly be described as green energy and as renewable energy, it does come with an huge environmental cost. The Columbia and Snake River dams are obstacles to both upstream and downstream migration of salmon. The dams also have had a negative effect on the migration of sturgeon.
Bonneville Dam was built by the US Army Corps of Engineers during the Great Depression of the 1930s. The facility is operated today by the Portland District
Bonneville Dam is located at the lower side of a landslide mass that is still unstable. In the Corp of Engineers aerial photo below, you can clearly see the huge tongue of material that nearly closes off the river above the dam. The slide occurred between 1670 and 1760 AD, and many authorities suspect that the great Cascadia subduction zone earthquake of January 26th, 1700 may have been a triggering event for the slide.
The photo above looks upstream toward the east. The numbered elements in the photo are:
1) The City of North Bonneville, Washington. The city was founded in 1933 to house construction workers building the dam. It was originally located nearer the numeral "4", and relocated to "1" in the 1970s to make way for the construction of the second powerhouse.
4) Bonneville Dam Second Powerhouse, completed in 1982. The numeral "4" rests on the landslide lobe that dammed the river a few hundred years ago. Native American legends speak of a "Bridge of the Gods". Originally dismissed by settlers as a myth, this bridge undoubtedly existed here for weeks as the Columbia backed up behind the landslide.
5) Bonneville Dam Spillway, completed in 1937.
6) Bonneville Dam First Powerhouse, completed in 1937.
7) Bonneville Dam (second) Lock, completed in 1993. The smaller original lock is just below the numeral "6".
9) I-84.
