Although the Long Lake Dam played a vital role in the development of the Spokane area, it had a very negative effect on the ecosystem of the area. Within the region, local environmental groups and citizens alike were angered by the development of the new dams because of the environmental impacts and cultural impacts that occurred, but in 1915, the United States saw electricity as being more important and an immediate necessity.
Before the dam was built, the Spokane River had an annual summer run of about a million chinook salmon. This genetic strain of chinook salmon typically weighed about 50 to 80 pounds, making them some of the largest fish in the northwest. After construction in 1915, the dam did not contain a fish ladder, cutting off the movement of salmon to the rest of the Spokane River. This was a catastrophe for the Native Americans who depended on the salmon year after year along the Spokane River for food and cultural purposes. In addition, the devastation of salmon population along the river was perpetuated by the construction of the Grand Coulee Dam in 1939, thereby blocking all upriver salmon runs.
Organic materials from along the river that wash downstream accumulate behind dams. As material starts to decompose, it consumes a large amount of oxygen. This can trigger algae blooms which create “dead zones” which are areas incapable of supporting life of any kind. Water temperatures in dam reservoirs can also differ greatly between the surface and depths below which can complicate survival for marine life evolved to handle natural temperature cycling. Dams can also release oxygen-deprived water with unnatural temperatures downstream which can send harmful conditions further along the river. In 2004, sections of the Spokane River were listed as impaired water bodies from the Washington State water quality standards. This was due to summertime low flows, caused by the dams, which led to low dissolved oxygen levels. In 2012, the Washington Department of Ecology identified a toxin algae bloom producing microcystin. This toxin in the blue green algae does not have deadly affects to humans, but it can affect animals and ecosystems. This is why maintaining adequate dissolved oxygen levels is important for supporting all natural aquatic life and keeping ecosystems stable.