79 River Power-Mid

River Power FOCUS Question How does hydroelectric power affect people and the environment?

水力发电如何影响人类和环境?

There's Energy in That Water Have you ever raced through rapids in a raft or watched waves crash on a beach? If so, you know that moving water has power. People harness that power to make energy. Electricity produced from moving water is called hydroelectric power. You might also know it as hydropower or hydroelectricity. Moving water is a very useful energy resource. Not only is it abundant and renewable, but it's also right where people need it most. Many towns and cities are located near an ocean or river. People use ocean waves and tides to make electricity. But most hydroelectric power in the world is generated using rivers. Wowser! For thousands of years, people used the energy of moving water to turn wheels and grind grains such as wheat. Some still do today!

你曾经乘着木筏在激流中奔跑过吗?你曾目睹过海浪撞击海滩吗? 如果是这样，你就知道流动的水是有力量的。 人们利用这种能量来制造能量。 由流动的水产生的电叫做水力发电。 你可能也知道它是水力发电或水力发电。 流动的水是一种非常有用的能源。 它不仅储量丰富、可再生，而且恰好是人们最需要它的地方。 许多城镇靠近海洋或河流。 人们利用海浪和潮汐发电。 但世界上大多数水力发电都是利用河流产生的。 老古板!几千年来，人们利用流动水的能量来转动轮子和研磨小麦等谷物。 有些人至今仍在这样做!

It Starts with Gravity Hydroelectric power production begins with the force that gets water moving— gravity. Earth's gravity pulls water downhill. Water flows from higher to lower land as runoff. Runoff collects in streams that flow into rivers and eventually flow into oceans. Fast-flowing water in a large river with a large drop in elevation has a lot of kinetic energy from the motion of the water. That's why hydroelectric power plants are often built on such rivers. To harness all that energy, people build a dam to control how the river flows. The dam blocks the river and forms a lake for storing water called a reservoir. Do You Know? Most dams are not built for generating electricity. They are built to control floods and irrigate crops.

水力发电始于使水运动的力——重力。 地球的重力把水拉下山。 水以径流的形式从高地流向低地。 径流聚集在小溪中，流入河流，最终流入海洋。 在一条高度大幅下降的大河中，快速流动的水从水的运动中获得了大量的动能。 这就是为什么水力发电厂经常建在这样的河流上。 为了利用所有的能量，人们建造了一座大坝来控制河流的流动。 大坝挡住了河流，形成了一个储存水的湖泊，称为水库。 你知道吗?大多数水坝不是用来发电的。 它们是用来控制洪水和灌溉农作物的。

Gravity pulls water from the reservoir into a large pipe inside the dam. At the end of the pipe is a turbine— a fan-shaped machine with large blades. The water turns the turbine blades, which turn the shaft of a generator. The generator uses strong magnets to convert this motion into electricity. After flowing through the turbine, the water moves through another pipe, exits the dam, and continues down the river. What happens to the electricity after it leaves a hydroelectric power plant? It travels through a system of stations, machines, and power lines. The lines bring electricity to communities near and far. They supply homes and businesses with energy to power appliances, computers, and lights.

重力将水从水库拉入大坝内的一根大管道。 在管道的末端是一个涡轮——一个有大叶片的扇形机器。 水推动涡轮叶片转动发电机的轴。 发电机利用强磁铁将这种运动转化为电能。 水流过水轮机后，穿过另一根管道，离开大坝，继续往下游流。 电力离开水力发电厂后会发生什么? 它通过一个由车站、机器和电线组成的系统传播。 这些电线将电力输送到远近的社区。 他们为家庭和企业提供能源，为电器、电脑和照明供电。

Pros and Cons There's a lot to like about hydroelectric power. It uses water, an abundant renewable resource that won't run out. It can be used in most parts of the world— anywhere rivers flow. It creates reservoirs that provide water for drinking, irrigation, and recreation. Reservoirs help protect against dangerous floods. They also store water for use during droughts. Hydroelectric power plants are "cleaner" than power plants that burn fossil fuels such as coal, oil, or gas to produce electricity. Burning these fuels releases greenhouse gases and other air pollutants. These pollutants contribute to global warming, smog, and acid rain. Hydroelectric power is produced without releasing greenhouse gases and other air pollutants. Hydroelectric power does have some drawbacks, however. Dams cost a lot to build, and they change the land and water above and below them.

利与弊水力发电有很多可取之处。 它使用的是水，一种丰富的可再生资源，不会枯竭。 它可以在世界上大部分地区使用——任何河流流经的地方。 它建造了水库，为饮用、灌溉和娱乐提供水。 水库有助于抵御危险的洪水。 它们还储存水以供干旱时使用。 水力发电厂比燃烧煤、石油或天然气等化石燃料来发电的发电厂“更清洁”。 燃烧这些燃料会释放温室气体和其他空气污染物。 这些污染物导致了全球变暖、烟雾和酸雨。 水力发电不会释放温室气体和其他空气污染物。 然而，水力发电确实有一些缺点。 大坝的建造成本很高，而且它们改变了上面和下面的土地和水。

Constructing dams and creating reservoirs cover land with water. These actions destroy natural habitats. Sometimes reservoirs cover towns, farms, and archaeological sites. People lose their homes, food, and heritage. Drowned vegetation can rot and release methane, a greenhouse gas. Less flooding happens on farmlands along rivers. Floods no longer deposit silt, which contains nutrients needed to help crops grow. Fish populations decline when dams block fish from swimming upstream to reproduce. Turbines injure or kill fish that swim through them. Dams also block water flow downstream. This can harm habitats by changing the water temperature and quality. Wowser! Some dams have elevators for fish! The elevators lift salmon and other migrating fish up and over the dams so they can spawn upstream.

修建水坝和水库使土地被水覆盖。 这些行为破坏了自然栖息地。 有时水库会覆盖城镇、农场和考古遗址。 人们失去了家园、食物和遗产。 被淹没的植被会腐烂并释放出温室气体甲烷。 沿河农田的洪水较少。 洪水不再沉淀淤泥，淤泥中含有帮助作物生长所需的营养物质。 当大坝阻止鱼类逆流繁殖时，鱼类数量就会下降。 涡轮机伤害或杀死了游过它们的鱼类。 大坝也会阻挡水流向下游。 这可以通过改变水温和水质来破坏栖息地。 老古板!有些水坝有鱼的升降机!电梯将鲑鱼和其他洄游鱼类提升到大坝上方，以便它们在上游产卵。