User:Cdmhume/sandbox

The Columbia River has the greatest annual drainage as compared to all other rivers along the Pacific coast. Before the introduction of dams to the river, the changes in water level rose and fell predictably with the seasons and a nine meter displacement existed between the spring snowmelt highs and fall lows. After the dams were built, however, the river changed unpredictably and in some areas the previous maximum and minimum water levels were altered by several tens of meters. No longer linked to the seasons, water conditions became subject to United States power demands. After the damming, the water during high floods began to cover much of the valley’s arable land - carrying with it fertile soil when the water retreated and leaving agricultural land useless

From 1965 to 1969, 27, 312 acres were logged along the Columbia River to remove timber from the new flood plain. The slashing of vegetation along the shoreline weakened soil stability and made the land susceptible to wind erosion, creating sandstorms. Conversely, in wet periods, the cleared areas turned into vast mud flats.

The introduction of a dam affects every living thing in the surrounding area, both up and downstream. Upstream change is obvious as water levels rise and submerge nesting grounds and migration routes. As water levels in storage reservoirs change throughout the year, aquatic habitat and food source availability become unreliable. Plankton, a main staple of salmon and trout’s diet, is especially sensitive to changes in water level. Nutrient rich sediment, that would previously have flow downstream, becomes trapped in the reservoirs above dams, resulting in changes in water properties and temperatures on either side of the barrier. A difference in water temperature of 9 degrees celsius was measured between the Columbia and its tributary the Snake River. When silt settles to the bottom of the river or reservoir it covers rocks, ruins spawning grounds and eliminates all hiding place for smaller fish to escape from predators. Alteration in water quality, such as acidity or gas saturation, may not be visually dramatic, but can be deadly to certain types of aquatic life. The Columbia River, with it’s series of dams and reservoirs, is influenced by a complex combination of these effects, making it difficult to predict or understand exactly how the animal populations will react.

Salmon and Steelhead trout travel from the ocean upriver to various spawning grounds. The construction of multiple dams, however, threatened this fishery as the fish struggled to complete the migration upstream. Some dams along the Columbia River do have fish ladders installed, such as Rock Island and Bonneville Dams, but most do not.

The presence of a fish ladder does not guarantee successful fish migration, as was indicated by the confusion surrounding the John Day Dam in April 1968. Although it was built with a fish passage, the spring Chinook run was virtually non existent and hundreds of dead salmon were found below the dam, suggesting that the salmon could not find the ladder. A few months later, the Fish Commission reported 30,000 fish, around 20%, of the normal Sockeye run was missing between the Dalles and John Day dams and linked the loses to “super saturation of nitrogen”. At the same time, the summer Chinook run was experiencing a 40% disappearance. This trend is not unique to the John Day dam, as an over 70% decrease in upstream fish populations was also observed above the Bonneville, Priest Rapid, and Ice Harbor dams in 1965. The construction of dams lead to great confusion over exact impacts and precise fish population numbers. The destruction of fish habitat during the building of Grand Coulee dam was quite clear as 1,770 Km, (1,100 miles) of spawning ground were ruined. As a result, some are now reporting there are no longer any salmon living above the Grand Coulee dam.

Migration downriver is also problematic after dams are built. Pre-dam currents on the Columbia efficiently carried fry to the ocean, but introduction of dams and reservoirs changed the entire flow of the river, forcing the young fish to exert much more energy to swim through slack waters. In addition, many fish are killed by the dam turbines as they try to swim further downstream. It is unclear exactly how many fish are killed in the turbines, but estimates range between 8-12% per dam. If a fish hatches high upstream they will have to swim through multiple dams, leading to possible cumulative losses of over 50-80% of the migrating fry. While hatcheries appear to be quite successful for some species of fish, their efforts to increase fish populations will not be effective until up and downstream migration is improved. There is no one solution to improving the salmon and trout populations on the Columbia as it is the cumulative effects of the dams that are killing the fish.

In the late 1940s, the BC Fish and Wildlife Branch began studying the impacts the dams were having on the area’s animal inhabitants. Their findings resulted in a small sum being designated for further research and harm mitigation. Their work, in collaboration with local conservation groups, became focused on preserving Kokanee stock jeopardized by the Duncan Dam which ruined kilometers of spawning grounds key to Kokanee, Bull Trout, and Rainbow Trout survival (gov, 192). Since Rainbow and Bull Trout feed on Kokanee, it was essential Kokanee stock remained strong (gov). As a result, BC Hydro funded the construction of Meadow Creek Spawning Channel in 1967, which is 3.3 Km (2 miles) long, and at the time was longest human-made spawning ground and first made for fresh water sport fish. The channel supports 250,000 spawning Kokanee every year, resulting in 10-15 million fry, with the mean egg to fry survival rate at around 45%. BC Hydro has also provided some funding to Creston Valley Wildlife Management Area to help alleviate damage done by Duncan Dam to surrounding habitats. The area is a seasonal home to many unique bird species, such as Tundra Swans, Greater White-Fronted Geese and many birds of prey. Such species are sensitive to changes in the river as they rely on it for food and their nesting grounds are typically found quite close to the water. BC Hydro, in partnership with the Province of BC and Fisheries and Oceans Canada, has also been contributing to the Columbia Basin Fish and Wildlife Compensation Program since 1988.