Vocabularies

First of all, study vocabularies. You can find them in your study materials (Studijní materiály - Rivers), or you can use the follow link.

HUMAN ACCESS TO WATER RESOURCES

  The fresh water is the world's most important natural resources. We use it to brush our teeth, to wash our clothes, to water the garden, to fill the swimming pool and, of course, we drink it. But we also dump our wastes in fresh water and flush them away when we lift a plug, press a button or drain wastes into a river, lake or sea. 

Water is what makes Earth a unique planet - water covers much of the Earth's  surface, and all forms of life depend on it.  Although 70 per cent of the Earth is covered with water, only a small proportion, about 2.5 per cent, is fresh water. The rest is salt water. Most of the fresh water is stored in the ice caps and glacier at or near the Poles, as well as underground. As a result, less than 0.01 per cent of the world's total fresh water supply is available for humans. Humans have access to this fresh water naturally in rivers, lakes and shallow underground sources, and through built reservoirs and other water storage devices. 

Water is a renewable resource. This means that if water is used and managed properly it can be put back or renewed. Water moves through the atmosphere, land, rivers and oceans in the water (or hydrological) cycle.  However, within this natural cycle, humans trap some of the water that falls as rain and use it for range of purposes before returning it to the cycle. Access to water  is also a basic human right. Despite this, about one-sixth of the world's population does not have this access. One of the most significant impact of this is poor sanitation - this affect children's health in particular.

How we use water?

RIVER ACTION

 

River factors involved in erosion: A river rises (begins) at its source. It flows downslope (its course) and enters the sea at its mouth (estuary). Rivers flow quickly down steep slopes. They erode the land and transport eroded material from highland to lowland areas. How quickly they erode the land depends on three things. Firstly, the hardness of rock - soft rock erodes faster than hard rock (soft chalk is used to mark hard blackboards). Secondly, the volume (amount) of water - rivers with large volumes of water, such as rivers in flood, erode faster than those with less water. Thirdly, the speed of river water - fast-flowing rivers erode more powerfully than slower-flowing rivers.

 

River processes involved in erosion: There are four important processes involved in river erosion. Hydraulic action describe the force with which moving water breaks off pieces of rock and soil from the bed and banks of river's channel. This broken-off material is then carried downstream and is called the river's load. Next, attrition is when boulders and other material being carried by the water collide and break up. Then, abrasion is when the river then uses its load to wear away (erode) its bed and banks, making its channel deeper and wider. Lastly, solution is when acids, such as carbonic acid (rainwater) dissolve some rocks, such as limestone, and erode the rock, much like what happens to some tablets in a glass of water.

 

Transportation of eroded material: There are four ways rivers transport materials downstream. Firstly, the lighter particles are carried in suspesion - they are lifted and carried along by the water, Similarly, heavier particles, such as sand and gravel, are bounced along the river bed. This is called saltation. Additionally, the heaviest particles slide or are rolled and dragged along the river bed. This is called traction. Finally, some materials are dissolved and are carried in solution.

 

The Three Gorges, China

  The Three Gorges Dam is the world’s largest hydropower project and most notorious dam. The massive project sets records for number of people displaced (more than 1.2 million), number of cities and towns flooded (13 cities, 140 towns, 1,350 villages), and length of reservoir (more than 600 kilometers). The project has been plagued by corruption, spiraling costs, technological problems, human rights violations and resettlement difficulties. 

Large-scale water project, including dam building, began in China after the communist revolution in 1949. Since that time, all China's major rivers have been dammed in effort to control the availability of fresh water for agriculture, industry, power production and flood control.

The Three Gorges Dam has dramatically altered the Yangtze River, flow into the Yellow Sea, north of Shanghai

Ultimately, the Three Gorges reservoir (the area of stored water behind the dam) covers 1045 square kilometers and stretch 663 kilometers. This is the largest inundated area by any single project in the world. 

 

There are some exercises for you. Go through them! You can find them in Study Materials (Studijní materiály -> Odpovědníky) or you can use the follow link.