The negative externalities associated with the construction of the Hetch Hetchy Reservoir include:
- Destruction of the natural Hetch Hetchy Valley, which was a unique and beautiful glacial valley within Yosemite National Park. The dam flooded the valley, submerging forests, meadows, and natural habitats, which opposed the purpose of a national park to preserve land for public use and recreation.
- Loss of ecosystem functions such as disruption of fish migration, altered river flow, and trapping of sediment and nutrients, which adversely affected aquatic and riparian ecosystems.
- Alteration of water quality due to the creation of a slow-moving reservoir, potentially resulting in abnormal temperature fluctuations, algal blooms, and decreased oxygen levels harmful to sensitive species.
- Controversy over lost recreational opportunities and scenic beauty, impacting public enjoyment and environmental conservation values.
- Violation and controversy regarding legal aspects like the Raker Act and agreements about the use of water and power generated from the dam for public vs. private interests.
- Economic and logistical challenges related to the dam, including high costs of potential removal, transport of demolished materials, and need for alternative water storage and filtration if the dam were to be removed.
- Displacement of wildlife and destabilization of the natural ecosystem in the valley, requiring concerted efforts for restoration if the dam were removed.
In essence, the construction of the Hetch Hetchy Reservoir caused environmental degradation, loss of natural and recreational resources, legal controversies, and ongoing debates about conservation versus utilitarian uses of nature.
