Name: Yuzhu Gong Due Date: 2015/1/13
Article Title: Down Go The Dams
Author/Source: Scientific American
Article Title: Down Go The Dams
Author/Source: Scientific American
A: List major ideas, concepts or key points - point by point
- At the start of the 20th century, Fossil Creek was a spring-fed waterway sustaining an oasis in the middle of the Arizona desert.
- The river and its surrounds also attracted prospectors and settlers to the Southwest.
- As with all things natural, reality often proves far more complex and intricate than people anticipate.
- Hydroelectric power makes up 20 percent of the globe’s electric supply, and the energy is largely clean and renewable, especially when contrasted with other sources.
- In the U.S., where hydropower dams must be relicensed every 30 to 50 years, the rate of dam removal has exceeded the rate of construction for the past decade or so.
- The release of sediments trapped behind a dam’s walls can choke waterways, muddying the environment and wiping out insects and algae, which are important food for fish.
- This wave of turbidity can also eliminate habitat for sessile filter feeders, such as freshwater mussels.
- Sediments that are not washed downstream can become problematic as well.
- The fossil creek restoration project offers a prime example of the kind of planning that could help minimize the damaging effects of dam removal.
- They also trap leaf litter, a crucial food source for the river’s denizens—one that the presence of manmade dams often eliminates by trapping it permanently behind the barrier.
- If the sediments contain high levels of pollutants, the cost of removing them—especially from remote locations—has to be weighed against the ability of the waterway to wash them away.
- If successful, this strategy could become routine, especially in smaller streams where chemical treatment is feasible.
B: Summarize the author's main point or idea
Summary of Author's Main Points:
Those of us who have witnessed many of the unexpected consequences of dam removals are now using that knowledge to try to minimize negative results in the future. Dams control flooding, and their reservoirs provide a reliable supply of water for irrigation, drinking and recreation. Some serve to help navigation, by stabilizing flow. The structures ruin vistas, trap sediments (needed for deltas, riverbanks and beaches), stymie migratory fish and destroy ecosystems in and around waterways. Biologists have also recorded unexpected problems that even today the striped bass fishery remains closed because of high levels of PCBs. Often the biggest issue facing managers is how to contend with what can be a massive accumulation of dirt and debris. If the sediment load is very high and the river’s flushing capacity low, engineers might opt to remove the dam in stages, allowing small amounts of sediment to be released at a time.
Summary of Author's Main Points:
Those of us who have witnessed many of the unexpected consequences of dam removals are now using that knowledge to try to minimize negative results in the future. Dams control flooding, and their reservoirs provide a reliable supply of water for irrigation, drinking and recreation. Some serve to help navigation, by stabilizing flow. The structures ruin vistas, trap sediments (needed for deltas, riverbanks and beaches), stymie migratory fish and destroy ecosystems in and around waterways. Biologists have also recorded unexpected problems that even today the striped bass fishery remains closed because of high levels of PCBs. Often the biggest issue facing managers is how to contend with what can be a massive accumulation of dirt and debris. If the sediment load is very high and the river’s flushing capacity low, engineers might opt to remove the dam in stages, allowing small amounts of sediment to be released at a time.
C: Reaction to the article
My Own Thoughts on the Topic:
Societies will continue to balance the pros and cons of dams, weighing their utility and benefits against their destructive costs. And scientists must continue to learn about how best to remove dams so natural ecosystems and human communities both can thrive. In most cases, controversy about decommissioning arises—and sometimes the debate is unexpected. With compromises such as these, along with further ecological insights and more flexible engineering, it seems possible to think of the world’s waterways as ultimately fulfilling their promise for all parties—from plants to people.
My Own Thoughts on the Topic:
Societies will continue to balance the pros and cons of dams, weighing their utility and benefits against their destructive costs. And scientists must continue to learn about how best to remove dams so natural ecosystems and human communities both can thrive. In most cases, controversy about decommissioning arises—and sometimes the debate is unexpected. With compromises such as these, along with further ecological insights and more flexible engineering, it seems possible to think of the world’s waterways as ultimately fulfilling their promise for all parties—from plants to people.
