The 4 hydroelectric dams on the lower snake river. This has been a question for about 10 years now.

The map below shows the location of these 4 dams:

The image below is the Lower Granite Dam:

Contrary to popular perception, Dam breaching doesn't mean a catastrophic explosion of the concrete dam. Much as one could sell tickets to an event like that, dam breaching on the Snake River Dams is much more benign and involves removing the earthern part of the dam (which is on the left side of the image above)>

Independent of your own personal feelings on the matter, it is generally useful to construct a Pro/Con Table that centers on this issue. For example,

The arguments in the Pro section are more speculative as its unclear if dam breaching would accomplish these goals. Certainly in the long term (50 years) this would happen, but how long would it take for the river to resume its natural state? Moreover, refering to the Map above, if the primary goal is to restore Salmon runs - then shouldn't the 4 dams on the Columbia river, below where the Snake enters it, also be breached?

Also, before one actually breaches, shouldn't one properly assess the current efforts at helping restore salmon runs?

Current Status of Salmon Migration and Survial Rates as measured by the National Marine Fisheries Service

• More than 50 percent of all fish traveling through the lower Snake River (up to 15 million) are diverted and collected for transport. The remainder are left in river. The majority of transported fish travel by barge. Trucks are used only early or late in the salmon migration season, when the numbers of fish are very low.

  Despite all of the obstacles juvenile fish encounter, recent NMFS survival studies show that, with current mitigation measures, spring/summer chinook in-river passage survival is as follows:

  Survival:

  • The average survival through a dam and reservoir on the lower Snake River for juvenile salmon is in the mid-90th percentile (for example, spring/summer chinook passage through Little Goose Dam is 96 percent).

  • Cumulative survival for adult salmon through all four lower Snake River dams and reservoirs ranges from 88 to 94 percent. Per-project survival rate is 97 to 98 percent.

  • Cumulative survival for juvenile salmon through all four dams and reservoirs is over 80 percent

  • Cumulative survival for juvenile salmon through all eight dams on the Columbia/Snake River System ranges from 45 to 60 percent.

What is understood less is the indirect or delayed mortality of juvenile fish that may occur after they have passed Bonneville Dam. That mortality may have been caused by passing in-river through the hydrosystem, the series of eight dams and reservoirs from Lower Granite Dam to Bonneville Dam or from transportation of fish.

The most striking number in this measure of survival rates, is that, under the current system of transport, 80% of the juvenile salmon (those are the ones heade downstream to the Pacific Ocean) survive the transit. Thus, in principle, removing the 4 snake river dams can only add 20% to this survival rate and there are still 4 bigger dams for the juveniles to face.

Cost/Benefit Analysis is difficult and often driven by hidden agendas Save Fish vs. Lose of Jobs ?

Costs of dam breaching are difficult to estimate but are in the range of $1 billion and up.

Will it work?

Current Socio-Economic Benefits of these 4 Dams:

• Cheap electricity (a significant thing): Breaching of the 4 dams on the Snake river will lead to a regional power loss of about 5% that will lead to increase in utility bills by up to 10% not a big deal.

• Irrigating the Columbia Basin 30-40,000 acres likely will be lost (no more irrigation available).

• Flood control

• River navigation (barging)

Relevant other sources on this issue

The Primary Source read this entire document if you want to have an informed opinion on the subject.

Fact Sheet Financial Impact

A comprehensive argument for breaching

Recent Developments (April 2008)

A good overview of the debate

March 2007 assessment

A blog about the first dam breaching in the US

Four Alternatives Identified:

• Leave everything as is

• Maximum Transport of Juvenile Salmon barging/trucking

• Major system improvments full-length surface bypass collector at Lower Granite Dam

• Breaching: Free flowing 140 miles all facilities for transporting fish cease to operate. Important note! Only the earthen embankment section of each dam needs to be removed; not the concrete powerhouse, spillway and navigation locks. They would just cease to function.

Some possible undesireable consequences from Dam Breaching:

Remember that the salmon still have to negogiate 4 other dams on the Columbia River!

In the short term, when the dams are breached, the rapid lowering of the reservoirs could strand some fish in shallow pools that will eventually stagnate. In addition, high turbidity and sediment in the water could cause trauma and injury, and low water levels could expose more fish to predators.

In the long term, the resident fish population will be altered, as some species will not thrive in the faster flowing river. Declines are expected in crappies, peamouth, pumpkinseed, bluegill, yellow perch, bullheads, and largemouth bass. Other species, including the chiselmouth, redside shiner, speckled dace, suckers, sculpin, white sturgeon, northern pikeminnow, bull trout, and smallmouth bass might benefit from natural river conditions.

Dam breaching could result in significant movement of sediments. Estimates are that 50 to 75 million cubic yards of existing sediments may be eroded and moved downstream. The majority of fine-grain silts would move quickly in the first few years following breaching. The coarser sands would move slowly downstream over 5 to 10 years. These existing and future sediments could move freely downstream toward McNary Dam and may cause some temporary adverse effects on food supplies for fish and bottom-feeding aquatic organisms. In addition, silt and sand now accumulated behind the dams could cause damage to pumps, valves, and other water system components.

Resuspension of sediments following dam breaching could result in exposing chemical contaminants that have been contained in reservoir sedimentation. Three chemicals are of concern total DDT, dioxin TEQ, and manganese. Only total DDT has any potential for affecting the biological system. In addition, there is concern about heavy metals from Idaho mining industry and the nuclear waste from the Arco Reactor

What are the options for replacement power?