The increased use of hydropower is currently driving the greatest surge in global dam construction since the mid-20th century, meaning that most major rivers on Earth are now dammed. Dams impede the flow of essential nutrients, including carbon, phosphorus, nitrogen and silicon, along river networks, leading to enhanced nutrient transformation and elimination. Increased nutrient retention via sedimentation or gaseous elimination in dammed reservoirs influences downstream terrestrial and coastal environments. Reservoirs can also become hotspots for greenhouse gas emission, potentially impacting how ‘green’ hydropower is compared with fossil-fuel burning. In this Review, we discuss how damming changes nutrient biogeochemistry along river networks, as well as its broader environmental consequences. The influences of construction and management practices on nutrient elimination, the emission of greenhouse gases and potential remobilization of legacy nutrients are also examined. We further consider how regulating hydraulic residence time and environmental flows (or e-flows) can be used in planning and operation from dam conception to deconstruction.

自20世纪中叶以来，水力发电的日益使用目前正在推动全球大坝建设的最大猛增，这意味着地球上大多数主要河流都已被筑坝。大坝阻碍了基本营养物质（包括碳，磷，氮和硅）沿着河流网络的流动，从而导致营养物质转化和清除增加。在淤积的水库中，由于沉积或气态消除而增加的养分保留影响了下游的陆地和沿海环境。水库也可能成为温室气体排放的热点，有可能影响将“绿色”水力发电与化石燃料燃烧相比。在这篇综述中，我们讨论了筑坝如何改变沿河网络的营养生物地球化学及其对环境的广泛影响。还检查了建设和管理实践对养分消除，温室气体排放和传统养分潜在迁移的影响。我们进一步考虑如何在从大坝构筑到解构的规划和运营中使用调节水力停留时间和环境流量（或电子流量）的方法。