Dam construction Flashcards
Where is the drainage basin for the columbia river?
- 360,000 m2
spans across 7 states and 1 canadian province:
Stretches across Oregon, Idaho, Washington, Canada and meets the see in the north pacific
What is the significance of the columbia River Salmon?
- Economic: in 2005 Columbia River Salmon fishery is worth $142 million p.a. to local economy
- Cultural: ‘without salmon returning to our rivers, we would cease to be Indian People’.
- ecological: food webs/ salmon life cycle is Anadromous. There is a strong nutrient/ biomass link between ocean and river ecosystems
- Chum Salmon
- Coho salmon
- Pink Salmon
- Sock eye salmon
- Chinnok Salmo
- Steelhead
Prior to 1800 between 10-16 million salmon returned to the Columbia each year
What are some of the memorable dams built along the columbia river?
- Rock Island 1932
- Bonneville- 1938
- Little Goose
- Ice harbour
What are the benefits of the dam?
- HEP=- 87% of electricity production in washington state
- Irrigation- Water from Grand Coulee irrigrates ca 500,000 acres
- Flow regulations
- Flow control
- Transportation- Barges can navigate more than 450 miles
- Recreation- e.g. wind surfers from Seattle/ Portland
Jobs and Livlihoods depend on dams
Negative impacts of dams on salmon?
- Alter flow regimes
- Loss of water through Irrigation
- Flooding salmon Habitat
- Impediment to fish
- Delayed Migration
- Increased predation and stress
- Damage to fish that pass through the turbines:
>blade strike
> Large pressure fluctuations
> Shear forces
> Turbulent waters disorientating fish
What were some Historic precedents of English Mitigation?
- The kings gap- a statue from the 12th C
- English rivers must be kept free of obstructions so that a well fed 3 year old pig can stand sideways without touching either sides - The Magna Carta- a document King John was forced to sign in 1215
- Contained a provision for removing weirs
- To protect salmon for use as a public good through all of england - The salmon and freshwater Fisheries Act 1975
Section 22 - Prohibits the sale of salmon or trout between 31 August to 1 February.
Section 23 - Prohibits the export of salmon or trout unless previously approved by HM Customs and Excise.
Section 9 to 15 - It is the duty of the waterway owner that when constructing dams, screens or sluices to provide and maintain a facilitating fish pass for migrating salmon or trout. These must remain undisturbed and unfished by everyone. Fish passes must be altered by any way the water authority wishes.
Historic mitigation in Eastern USA
- Between 17th and 19th centuries, mills were the main source of mechanical power
- Mill dams requried to divert water through the Mill system
- In addition to blocking water, they also blocked fished
- Complaints fro citizens accustomed to obtaining fish
- Early 18thC dams had to have openings to let fish pass during their migrations
Western seaboard USA mitigation?
- Fish and Wildlife Coordination act, 1934
- Federal Power Act 1935
- Mitchell Act 1938
- Endangered Species Act, 1973
- The Pacific Northwest Electric Power Planning and Conservation Act, 1980
How might we assess the impact of the dams on salmon population?
Need a baseline data for pre-dam era
- Search for historic data
- Use of an appropriate control site
- Conduct empirical studies
- Modelling
What is the commercial salmon harvest trend?
- Between 1865 and 1977- salmon has significantly reduced
- Peaked late 1800s
What are some significant Chinook trends?
Fluctuation in the amount of fish returning to Bonneville Dam since it was built 1938
- more than doubles to 900 (000s) by 2002
- Amount of escapees are reducing
What do we know today?
History:
- Historic salmon returns: 10-16 million adults p.a.
- Chinook salmon runs on the columbia were the largest in the world
Today:
Runs have declined by 90% (around 1.5million returns in the 1990s)
- upturn in returns during late 1990s- early 2000s (ocean conditions? Improvements in management/ mitigation?)
What are the factors that affect population status?
- Habitat
- Hydropower
- Harvest
- Hatchery
- Ecological conditions
- Climate change
- Predation
- Introduced bacteria
(these produce trends and abundance)
What are the historic mitigation methods?
- Fisher ladders
- Concrete hatcheries
- Transportation
What are the confounding factors that can seriously distort interpretation?
- Ocean conditions
- More dams constructed
- Improvements in mitigation/ Management.
Catch data alone can be misleading (we need catch / unit effort)
