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  • General

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  • 小溪与河流

    A group of people enjoying whitewater rafting on a fast-moving river.
     

    What makes this river so much fun to raft?
    ::是什么让这条河如此有趣?

    Whitewater rafting is a popular recreational activity. The  river  is fast because it is in the  mountains  traveling downhill. There is a lot of  water  from  snow  melt higher up. Sometimes water is added from springs. Did you ever go whitewater rafting? It's fun!
    ::白水漂流是一种流行的娱乐活动。 河水是快速的, 因为它在山上下山。 雪融得更高, 有很多水。 有时水会从泉水中加水。 你曾经去过白水漂流吗? 这很有趣!

    What Are Streams and Rivers?
    ::什么是溪流和河?

    A  stream  is a body of  freshwater  that flows downhill in a channel. The channel of a stream has a bottom, or bed, and sides called banks. Any size body of flowing water can be called a stream. Usually, though, a large stream is called a  river .
    ::溪流是一条流到下坡的淡水体。 溪流的河道有底部或床和两边称为河岸。 任何水流体大小都可以称为溪流。 不过,通常大溪流被称为河流。

    Features of Streams and Rivers
    ::溪流和河流的特点

    All streams and rivers have several features in common ( Figure   ). The place where a stream or river starts is its  source , or  headwaters . The source might be a spring, where water flows out of the ground. Or the source might be water from melting snow on a mountaintop, like the stream pictured below ( Figure   ). A single stream may have multiple sources.
    ::所有溪流和河流都有共同特征(图 )。 溪流或河流的起点是其源头或源头。 源头可能是泉水, 水流从地面流出。 源头可能是山顶融雪产生的水, 如下图(图 ) 。 单一溪流可能有多个源头。

    A stream flows from a rocky area through a forested landscape under a cloudy sky.
     
    A stream flows fast and steep where it originates in the mountains. This stream, in Glacier National Park in Montana, is coming from snow melt.
    River features: source, tributaries, floodplain, meanders, mouth, and delta.
     
    Water in a stream flows along the ground from higher to lower elevation. What force causes the water to keep flowing?

    A stream or river ends at its mouth, where it flows into a body of water, such as a  lake  or an ocean. As the stream flows into the body of water, the current slows down and drops the  sediment  it was carrying. The sediment may build up to form a  delta . If the mouth of a stream flows into the ocean, it forms an  estuary , where the mixing of fresh and salt water creates unique  ecosystems .
    ::溪流或河流以其口为尽头,流入水体,如湖泊或海洋;河水流入水体时,水流放慢,沉积下降;沉积物可能形成三角洲;溪流的口流入海洋,形成河口,淡水和盐水混合形成独特的生态系统。

    Several other features of streams and rivers are also shown above ( Figure   ).
    ::上文还列出了河流和溪流的其他几个特点(图[...])。

    • Small streams often flow into bigger streams or rivers. The small streams are called  tributaries . Tributaries come together at a  confluence . A river and all its tributaries make up a river system.
      ::小溪流往往流向更大的溪流或河流。小溪流被称为支流。 支流汇合在一起。 河流及其支流组成了河流系统。
    • At certain times of  year , a stream or river may overflow its banks. The area of land that is flooded is called the  floodplain . The floodplain may be very wide where the river flows over a nearly flat surface.
      ::每年某些时候,河流或河流可能会溢出其河岸,洪水淹没的土地面积称为洪泛平原,河水覆盖面几乎平坦的地方,洪泛面积可能很大。
    • A river flowing over a floodplain may wear away broad curves. These curves are called  meanders . Pictured below is an example of this ( Figure   ).
      ::流过洪泛地带的河流可能会折损大曲线。 这些曲线被称为缓冲曲线。 如下图所示( 图 ) 。
    Aerial view of a meandering river through a green floodplain and ponds.
     
    A river meanders across an estuary in South Carolina.

    River Basins and Divides
    ::河流流域和鸿沟

    All of the land drained by a river system is called its  basin , or  watershed . One river system’s basin is separated from another river system’s basin by a  divide . The divide is created by the highest points between the two river basins.   that falls within a river basin always flows toward that river. Precipitation that falls on the other side of the divide flows toward a different river. A  continental divide  separates rivers that flow into different oceans.
    ::河流系统排水的所有土地都被称为流域或流域。 一条河流系统的流域因分裂而与另一条河系的流域分离。 分水岭是由两个河流流域之间的最高点造成的。 河流流域内部的分水岭总是流向河流。 分水岭的另一边的降水流向另一条河流。 大陆的分水岭将流向不同海洋的河流分隔开来。

    Pictured below are the major river basins in the U.S. ( Figure   ).
    ::以下是美国的主要河流流域(图)。

    Map displaying major river basins in the U.S., highlighting various watersheds.
     
    River basins in the U.S.

    Summary
    ::摘要

    • A moving body of water of any size is a stream. A river is a large stream.
      ::任何大小的移动水体是一条溪流,河流是一条大溪流。
    • A tributary begins at its headwaters on one side of a divide. Two tributaries come together at a confluence.
      ::支流从分界线一边的头水开始,两个支流汇合在一起。
    • A river ends at its mouth. If the river drops sediment, it may create a delta.
      ::河口尽头是一条河,如果河中沉降着沉积物,可能会形成三角洲。

    Review
    ::回顾

    1. Describe the features of a river from where it begins to where it ends.
      ::描述河流的特征,从河的起点到河的终点。
    1. What happens to two drops of water that fall on opposite sides of a divide?
      ::两滴水掉在分裂的对面会怎么样?
    1. Why does a tributary not cross over a divide?
      ::为什么支流不跨越分界线?

    Explore More
    ::探索更多

    Use the resources below (start at 0:49) to answer the questions that follow.
    ::使用以下资源(从0:49开始)回答下列问题。

     

     

    1. What is the tributary system? What does that mean in simple English?
      ::支流系统是什么?用简单的英语是什么意思?
    1. What does a tributary flow into?
      ::支流会流进什么?
    1. What do the tributaries in the Rocky Mountains near Woodland Park feed into? What does that flow into? And what does that flow into? And finally what does that flow into?
      ::伍德兰公园附近的洛基山脉的支流会形成什么?它会流入什么?它会流入什么?它会流入什么?最后会流入什么?
    1. At what point does a tributary meet a river?
      ::支流何时会遇到河流?
    1. What is the biggest trunk river in the U.S.?
      ::美国最大的干河是哪条?
    1. What is the end of the Mississippi River in the Gulf of Mexico?
      ::墨西哥湾密西西比河的尽头是什么?
    1. What is a delta?
      ::什么是三角洲?
    1. What is found in a delta?
      ::在三角洲里发现了什么?
    1. How did a delta get its name?
      ::三角洲怎么会知道它的名字?