STEM与日常科技·英语30篇（3）
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Hydroelectric Dams and Ecological Trade-offs
水力发电大坝与生态权衡
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Dams generate clean electricity by channeling flowing water through turbines that spin generators.
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But reservoirs flood forests and farmland, displacing communities and destroying habitats permanently.
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Fish like salmon cannot swim upstream past tall dams unless ladders or elevators are installed.
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Slower-moving reservoir water warms up and holds less oxygen, harming native aquatic species.
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Sediment that once fertilized downstream farms now piles up behind the dam, reducing fertility over time.
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Engineers now design 'fish-friendly' turbines with slower blades to lower mortality rates.
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Seasonal water releases mimic natural flow patterns to support downstream wetlands and spawning cycles.
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Small modular hydro projects avoid massive flooding but produce far less power per site.
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Decommissioning old dams restores rivers but requires careful sediment management to avoid pollution.
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Each dam project must weigh carbon-free energy against long-term biodiversity and cultural impacts.