By Emmerich Anklam, Annie Kong, Brian Ombonga, Andrew Parlier

 

A Brief Overview of the Lower Granite Dam

The removal of the four Lower Snake River dams is a highly contested topic. The Lower Granite Dam in particular raises a number of issues, from the flooding of Lewiston, Idaho, to fish migration.

One benefit of the Lower Granite Dam is hydropower, as the dam provides more than 800 megawatts each year. Another major benefit is navigation. Natural river conditions such as currents, snowfall, flooding, etc. can make it tough to travel inland. However, dams and locks provide a stable way to travel through river systems. In 2010, traffic through the navigation lock consisted of grains, petroleum products, fertilizer, wood products, and miscellaneous cargo that amounted to 1,041,700 tons.

Unfortunately, silt carried by the Snake River and the Clearwater River has accumulated behind Lower Granite Dam. Approximately three million cubic yards of sediment accumulates in the Lower Granite Reservoir annually. One important consequence of this buildup is the possibility of flooding in Lewiston. Downtown Lewiston is protected by levees, and in the future a flood will likely raise the water level in the Lower Granite Reservoir enough to overtop them.

The other problem is the dam’s effect on fish migration. The dam affects both upstream and downstream salmon migration but affects downstream smolt migration more substantially. 

This presentation discusses different options regarding the future of the Lower Granite Dam.

1. Status Quo: First is the “status quo” option, in which no new policies are being enacted. This plan offers minimal costs in the short run and does not require any immediate choices that will be controversial with the public. At the same time, flooding and fish migration remain completely unsolved by this policy.
2. Dam Removal: This option would immediately solve the issue of flooding in Lewiston as well as restore natural salmon runs. However, the transportation of agricultural products at the dam site as well as the dam’s substantial energy production would cease immediately.
3. Breaching: One other solution is a breach of the dam, which allows part of the dam to be removed. The process is usually done to allow fish passage and keep the dam's value as a monument to human ingenuity. However, it would result in loss of Lewiston as a seaport as well as the loss of hydropower production.
4. Removable spillway weirs: Large constructs called removable spillway weirs would help with the problem of downstream smolt migration. They would allow smolts to safely pass through the spillway. However, they are very expensive, with each weir costing between 16 and 22 million dollars.
5. Dredging: Another option is the dredging of sediment from behind the dam, which eliminates any worries of flooding in Lewiston, at least in the near future. However, dredging is wildly expensive, especially because the ongoing buildup of sediment requires that dredging be enacted continuously in order to be effective. 

Given the options and our limited knowledge of the subject, we suggest breaching the dam. This option solves the flooding issue in Lewiston as well as the fish migration issue. It would be a difficult solution to achieve, however, because it would eliminate Idaho’s only seaport as well as a large source of energy for the Bonneville Power Administration. While we see a breach as the best option for the Lower Granite Dam, it is important to note that each dam across the West is unique and options including removal must be evaluated independently for each.

Annotated Presentation Slides

Water management has long been a hot topic in the West. The arid climate not only necessitates irrigation but also leads to highly contested water rights. Dams were an early and oft-used solution to many issues--navigation, irrigation difficulties, power need. However, environmental, economic, and social concerns in modern society have led to the removal of many dams in Idaho and around the West. Current discussions around dam removal are now focused on the Lower Snake River. In this presentation, we will focus on the case study of the Lower Granite Dam in Lewiston. Built in 1972, the Lower Granite Dam was initially owned and operated by the Army Corps of Engineers with the purpose of providing hydropower and navigation lock.This dam forms part of the lower granite lake and extends almost 40 miles east to Lewiston. As Idaho’s only seaport, Lewiston is regarded as a federal investment for grain shipments. However, today Lewiston faces the challenge of rapidly rising water levels and faces the possibility of flooding if no action is taken. Resolving the issues surrounding the Lower Granite presents a daunting political task, with valid arguments on both sides.

One benefit of the four lower Snake River dams is hydropower. Together, the four dams provide over 3,000 megawatts of energy through hydropower, and the Lower Granite dam alone provides over 800 MW each year.

Another major benefit is navigation. Natural river conditions such as currents, snowfall, flooding, etc. can make it tough to travel inland. However, dams and locks provide a stable way to travel through river systems. In 2010, traffic through the navigation lock consisted of grains, petroleum products, fertilizer, wood products, and miscellaneous cargo that amounted to 1,041,700 tons.

Silt carried by the Snake River and the Clearwater River has accumulated behind Lower Granite Dam. It is estimated that 3 million cubic yards of sediment accumulates in the Lower Granite Reservoir annually. Currently sediment covers 55% of the reservoir, causing a rise in surface water level in the reservoir.

One important consequence of this sediment buildup is flooding in Lewiston. Downtown Lewiston is protected only by levees, which are designed for 5 feet of freeboard, meaning the height of a levee above the water level in the reservoir. At points distance between the water and the top of the levee is 1.5 feet. A flood will likely raise the water level in the Lower Granite Reservoir enough to overtop the levees.

The other problem is the effect on fish migration. The dam affects both upstream and downstream salmon migration, but the biggest effect is on downstream smolt migration. 

This presentation will discuss six options regarding the future of the Lower Granite Dam. The first three are mutually exclusive, while the remaining three are not.

First, we examine the “status quo” option. Because no new policies are being enacted, this plan offers minimal costs in the short run and does not require any immediate choices that will be controversial with the public. At the same time, flooding and fish migration remain completely unsolved by this policy. 

 

Far more controversial is a complete removal of the dam. Removal would immediately solve the issue of flooding in Lewiston, as well as restore natural salmon runs. However, the dam’s substantial energy production will cease immediately. Additionally, transportation of agricultural products, one of the main purposes of the dam when it was built, becomes nullified by the dam’s removal.

One other solution is a breach of the dam. A breach allows part of the dam to be removed. The process is usually done to allow fish passage and keep the dam's value as a monument to human ingenuity. However, it would result in loss of Lewiston as a seaport as well as the loss of hydropower production.

In 2001, 1,000 tons of prototype were installed to assist smolt migration downstream.This installation was named the best engineering accomplishment in 2003 by the American Council of Engineering Companies. However, removing spillway weirs comes with both advantages and disadvantages:

Advantages

• Makes large stride in helping solve downstream anadromous fish migration issues
• Removable--therefore variable and emergency viable
• Much more efficient at “fish passage per unit flow” than current methods
• Engineering marvel (personal interest)

Disadvantages

• Expensive to build (a comparable project at Ice Harbor dam was approximately $10 million)
• Estimated total cost for 2001 project was between $16 and 20 million
• NOT 100% effective

Another option is the dredging of sediment from behind the dam. Dredging would address the sediment buildup problem but not the migration of fish. In theory, extracting excess sediment from the river eliminates any worries of flooding in Lewiston, at least in the near future.

However, to work properly, dredging must not cease as long as the dam continues to exist. Sediment buildup behind the Lower Granite Dam averages 3 million cubic yards per year. A dredging operation would involve the removal of enough sediment to ensure that Lewiston will not flood, but any removal is a temporary fix for an unavoidable problem. Also, maintaining a dredging operation is very expensive. The Army Corps of Engineers’ cost estimates range wildly, but it is certain that dredging will cost millions of dollars annually. Assuming that the dam remains in place well into the future, the operation will have a cost on the order of hundreds of millions. 

The last alternative is the raising of levees. Flooding can no longer overtop the the levees once they are raised, and the residents as well as properties in the Lewiston area are saved. 

However, there are also disadvantages with the the raising. According to the U.S. Corps of Engineers, raising the levees 12 feet would cost more than $87 million.

There is no easy solution for the Lower Granite Dam. Over 32,000 people live in Lewiston and over 1 million tons of goods are shipped through the Lower Granite Dam navigation lock. This problem extends to the West at large and needs to be addressed in the near future. In our final analysis, we recommend the option of breaching. This option would avoid postponing the problem and has the least negative impact. However, the issue of dams should be looked at on a case by case basis; what works for the Lower Granite Dam may not be the best course of action for all dam removal debates

 

 

Works Consulted

A. Dan Tarlock. “The Legacy of Schodde v. Twin Falls land and Water Company: The Evolving Reasonable Appropriation Principle.” 3/15/2012.

Annex B. “Dam Embankment Excavation Plan.”

“Clearwater River: Removal of the Grangeville and Lewiston Dams in Idaho.” Dam Removal Success Stories.

Clive J. Strong and Michael C. Orr. “The Origin and Evolution of Hydropower Subordination Policy on the Snake River: A Century of Conflict and Cooperation.” HeinOnline.

“Dam Removal: Science and Decision Making.” The H. John Heinz III Center for Science, Economics, and the Environment.

Dave Piper, President and CEO, Pacific Northwest Generating Cooperative. “The Snake River Debate Continues.” http://www.pennenergy.com/pennenergy-2/enus/index/power/display.articles.powerengineering.volume-104.issue-6.features.the-snakeriver-debate-continues.html.

Glenn Seaberg, Allen Bradbury, Katie Slavin. “Idaho Model Watershed Project.” Prepared for U.S. Department of Energy and Bonneville Power Administration.

Idaho State Constitution. Article XV. “Water Rights.”

Jacqueline R. Papez. “Native (Hydro)Power: Alternative Avenues for Achieving Native Control of Natural Resources on Tribal Lands, with Focus on Hydropower Dams.” HeinOnline

Jeffrey H. Braatne, Stewart B. Rood, Lori A. Goater, Charles L. Blair. “Analyzing the Impacts of Dams on Riparian Ecosystems: A Review of Research Strategies and Their Relevance to the Snake River Through Hells Canyon.”

Johnnie N. Moore, Alicia S. Arrigora, Andrew C. Wilcox. “Impacts of Dams on Flow Regimes in Three Headwater Subbasins of the Columbia River Basin, United States.” Journal of the American Water Resources Association.

“Major Dams Within Columbia River Basin.” GIS Data. Bonneville Power Administration website.

Michael C. Blumm. “The Real Story Behind the Columbia Basin Salmon Debacle: Dam Preservation Under the Endangered Species Act.” A Book Review of Steven Hawley’s Recovering a Lost River: RemovingDams, Rewilding Salmon, Revitalizing Communities.

Robert L. Harris. “Narrowing the Local Public Interest Criterion in Idaho Water Right Transfers.”HeinOnline.

Stephen Higgs, Elizabeth Maclin, Margaret Bowman, Angela Bednarek. “The Ecology of Dam Removal: A Summary of Benefits and Impacts.” American Rivers.

“Stuck in the Mud: Growing Flood Risk, Growing Costs with Keeping the Lower Snake River Dams.” Save Our Wild Salmon.

The American Council of Engineering Companies. “Snake River Removable Spillway Weir Named Best U.S. Engineering Triumph.” March 25, 2003.

The Salmon Blog. “Far Fewer Sockeye are Bound for Redfish Lake this Year than Last on the Day we Remember Lonesome Larry’s Arrival 20 Years Ago.” 8/4/2012.

U.S. Army Corps of Engineers website. “Corps of Engineers Offers Spring Recreation Opportunities on Lower Granite Lake.”

U.S. Army Corps of Engineers Website. “Lower Granite Dam.”

U.S. Army Corps of Engineers website. “Surface Passage Systems and Removable Spillway Weirs: Lower Columbia and Snake River Dams.”

Water Quality Team, Reservoir Control Center, Columbia Basin Water Management Division, U.S. Army Corps of Engineers Northwestern Division. “Lower Granite Dam Informational Overview.” September 2009.

William L. Graf, John J. Boland, Douglas A. Dixon, Thomas C. Downs, John J. Kraeuter, Mary Lou Soscia, David L. Wegner, Philip B. Williams, Craig S. Wingo, Eugune P. Zeizel.

William L. Graf. “The Changing Role of Dams in Water Resources Management.” Universities Council on Water  Resources. Water Resources Update, Issue 126, Pages 54-59, November 2003.

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