Columbia River: Bonneville Dam, BPA, and ACOE
April 9, 1999

Hydrophiles continued its theme of seasonal relevance for field trips by focusing its spring 1999 trip on runoff. We traveled to Bonneville Dam, plus Bonneville Power Administration (BPA), and Army Corps of Engineers (ACOE) offices in Portland to learn about river planning and operations in the Columbia Basin, and current technical perspectives on the salmon crisis. Three students from Portland State University joined us in the first joint venture between Hydrophiles and the newly-formed PSU student chapter of AIH. The trip was a wonderful combination of probing, informative discussion; marveling at classic Columbia Gorge scenes, dam facilities, and computer model technology; and gaining career insights from the professionals we met. We learned quite a lot on the trip, as the following synopsis indicates. 

Columbia Basin Overview 
The Columbia Basin is over 250,000 square miles and includes parts of five western states plus British Columbia. Climate in the Basin varies considerably, but river hydrology is dominated by snowmelt from high-elevation areas, with about 80% of annual flow occuring April-July. About 61% of annual flow at Astoria comes from above Grand Coulee, 27% from the Snake R., and 12% from other tributaries. 

Dams on the Columbia are either run-of-river, or storage dams. Primary purposes for Columbia run-of-river dams are usually power and navigation, while for storage dams they are power and flood control. Total storage on the Columbia system is only 33% of mean annual runoff, compared to 250% for the Colorado Basin. Bonneville Dam (1937) is the lowermost dam on the system, and although it is run-of-river with little storage, it produces enough electricity for the needs of 1 million people. It was built not only to provide the official authorized benefits, but also to provide jobs during the Great Depression in a region where 50% of all employment was in the hard-hit timber industry. 

About 65% of the Pacific Northwest's electricity comes from hydropower. For all their negative impacts on aquatic ecology, the dams do provide a clean alternative to energy derived from combustion sources, an important fact in light of global warming. It won't be easy to subsitute clean alternatives, at least in the short run. Salmon travelling up the Columbia are able to swim as far as Grand Coulee on the mainstem, or Hells Canyon on the Snake R. Over $400 million is spent annually by federal agencies to improve fish passage on the Columbia. 

Salmon and Bonneville Dam 
There are four kinds of salmonids in the Columbia Basin: chinook, coho, sockeye, and steelhead. Of these, only fall Chinook are mainstem spawners, and the fall chinook run in the Hanford Reach is the only healthy wild fish run remaining. Total annual salmon runs in the Columbia Basin have declined from about 15 million at the turn of the century to about 0.5 million today--counting both salmon and steelhead, including hatchery fish. The total number of fish is similar to that during the 1940s, but only about 20% are wild fish. About half of all fish are barged or trucked around dams. 

Both adult fish moving upstream and juvenile fish moving downstream must successfully pass dams to survive. As we learned at Bonneville, the technology for guiding adult fish upstream has been relatively successful--fish ladders work well if the fish find them, and the North Powerhouse design incorporates multiple entrance routes to help guide the fish away from tailrace water and towards the fish ladder. At Bonneville, most fish use a submerged pipeline with an orifice placed about 100 m downstream of the dam. 

The picture for juvenile fish (smolts) moving downstream is much worse. The survival rate for juvenile fish travelling from the furthest upstream reaches on either the mainstem or Snake R. to the Columbia R. estuary is only about 50% (an estimate of the rate under natural conditions was unavailable). It is estimated that at least 2% of juvenile fish must return to spawn to maintain a run, and a higher percentage is needed to increase the run. Currently the return rate for runs above the dams is only 0.4%, while fish runs below the dams have a return rate of just 0.6%, highlighting the important role of ocean conditions in the overall picture. ACOE's goal for return rate is 2.5%. 

There are four routes for water to get by Bonneville Dam: turbines, spillway, bypass channel, and fish ladders. The first two routes pass the greatest flow of course, and pose hazards for migrating fish. The biggest problem for downstream passage at dams has always been keeping the fish away from turbines. It is believed that fish die in the 69 rpm turbines not from being struck by the blades, but through stress caused by pressure fluctuations in small gaps at the blade edges. We entered one of the turbine housings and stood in the space between the wicket gates and the generator, watching the shaft spin. New tighter-fitting blades have improved the survival rate from about 85% to 96%. 

Spillways provide the fastest passage for fish, and flows are allocated specifically for this. However, spillways do pose a problem in the form of nitrogen gas entrainment, which gives fish "the bends." Entrainment increases with flow, so during high flows, which run-of-river Bonneville cannot reduce, there is greater mortality. The 1995 Biological Opinion, a ruling document written by National Marine Fisheries Service (NMFS), states that there should be 95% survival at every dam, with 80% of the downstream passage occuring via non-turbine routes. At Bonneville, ACOE will strive towards this goal primarily through development of better surface collectors that guide fish away from the front of the dam and into the bypass canal. Over $22 million will be spend during the next two years developing and testing a prototype. 

In the Willamette Basin, storage reservoirs may be used to augment flow specifically for downstream salmonid migration. Lowering of reservoirs in summertime would have negative impacts on flatwater recreation, but at the same time would benefit whitewater recreation. 

A group of biologists have said that breaching of the four lower Snake River dams is a necessary step for salmon recovery in that basin. ACOE is currently studying this option and will release its report during the fall of 1999. The amount of power that would be lost from the four Snake dams is 1.2 GW, or a bit more than Bonneville alone. Of more concern is the loss of navigation, which would shift bulk freight from barges to more expensive rail service. ACOE has also begun looking at the lowering of the John Day reservoir, which would significantly increase the amount of spawning habitat in that reach. It would also speed river flow through that reach, which has the slowest current and greatest amount of squawfish, a predator of salmon smolts. Negative impacts would be loss of power production and flood control, and increase of irrigation costs due to greater pumping lift. Both actions would ultimately require an act of Congress, and currently the northwest delegation's attitude on these ideas ranges from neutral to bitterly opposed. 

River Flow Planning and Management 
BPA performs weather, streamflow, and power forecasting in its Portland office. A very high degree of coordination is essential to keeping the whole system functioning well with respect to power generation, fish passage, flood control, and a whole host of other activities. At the center of operations is a lumped-parameter, deterministic streamflow model that breaks up the basin into about 200 subareas and runs on a 6-hour time step. The model simulates snowpack dynamics with only precipitation and maximum and minimum temperatures for boundary conditions. It performs best during periods of gradual change, and worst during rain-on-snow events. The Willamette subbasin is much harder to simulate well because only 25% of the flow is controlled by dams, and basin forecasting requires much more "art." The model contains about 1 million lines of code and uses 24 GB storage. Each day, a BPA team work for several hours to update their 10-day forecast with new meteorological and river information. Sloshing of short-length reservoirs can occur between dams when flows are changed, which can confound water level monitoring and forecasting. Incredibly, the Columbia acts like a bathtub to a degree! 

As of this writing (4/12/99), there is a record snowpack in the Columbia Basin, with 196% of average snow water equivalent in the Willamette Basin, for example. Spring has been very cool with continued snowstorms into April. Too rapid a melt of such a large snowpack could cause flooding, yet officials are not too concerned, because the likelihood of getting a warm tropical storm to drive a rain-on-snow event is quite small compared to earlier in the winter. 

A final perspective we gained on the future of the Columbia management system is that deregulation of the energy industry has made planning more difficult and is an ominous development from the standpoint of salmon recovery. Power marketing has become very complex, and lower wholesale prices and unstable demand do not lead in an obvious way to continued and increased efforts to help fish. 

Thanks to all of the BPA and ACOE staff who took time to prepare presentations and meet with us; to Tim Link and Chan Modini for organizing such a great trip; and to Christine May for driving the big OSU van. Drawings were reproduced from the ACOE brochures entitled "To Save the Salmon," and "Water Management For the Pacific Northwest Reservoir System." 

Trip schedule and web links to agencies. 

--Scott Waichler 

Last modified: Wednesday, 11-Aug-1999 15:02:36 PDT
Comments to webmaster
OSU Disclaimer