Water Sources and Rivers PDF

## 4.1 Where does our water come from? - Can you see your raindrop's journey through the water cycle? - It's a cycle - the same water keeps going around and around... **Key word** - Water cycle - Ground water - Surface water - Springs - Aquifer - Waterholes The water you use every day comes from...

## 4.1 Where does our water come from? - Can you see your raindrop's journey through the water cycle? - It's a cycle - the same water keeps going around and around... **Key word** - Water cycle - Ground water - Surface water - Springs - Aquifer - Waterholes The water you use every day comes from two different sources: the ground or the surface. ### What is ground water? Ground water is water that is under the ground. But, how does it get there? - Bores are large metal wells or holes, drilled into rocks to bring the water up from under the ground. - This water may not be cleaned or filtered so it shouldn't be used for drinking but it can be used for watering the garden and washing cars or clothes. - Only bore water that has been tested by a specialist and approved can be used for drinking. When it rains, water lands on the ground and starts to soak through the earth. It moves through the layers of soil deeper into the rocks where eventually it can't go any further. The water collects and forms an 'aquifer'. Most of our water comes from aquifers. To use the water, we need to bring it to the surface. This can be done by digging a well, creating a bore or using pumps. ### What is surface water? Surface water is water that collects on the surface of the Earth after it rains. This could be in a river, lake, dam, reservoir or waterhole. The ocean is also a form of surface water, but it is salty, not fresh. ## 4.2 Where does our water come from? Surface water is not safe to drink as it may contain bugs, dirt, rocks, minerals and/or chemicals. People may swim in these places, animals will drink from them and bathe in them so they may even contain animal droppings. This water has not been cleaned and filtered, so you should not drink it. Rainwater tanks are also a form of surface water and are a great way to collect and conserve water, but the water from them may not be safe to drink. It can have bugs, dirt and/or minerals in it. Also, anything that is on the roof of your house, or in your gutters, can end up in the rainwater tank. This water can be used for watering the garden and washing cars or clothes. If this water is used for drinking you need to ensure that all gutters are cleaned and free of leaves and animal droppings. ### Are there any other sources of water? Waterholes, rock holes and springs also provide us with water and are a combination of ground water and surface water. ### Rock holes Rock holes are surface water features where water is held in a rock or rocky area. Rock holes are of significant value to Aboriginal people living in arid areas of Australia. They provide a crucial water supply in an otherwise dry landscape where there is little permanent surface water, assisting in travel across the landscape and access to a larger range of resources. ### Springs Springs occur naturally where water comes to the surface from an underground aquifer. The amount of water that flows from springs can depend on many factors including the water pressure in the aquifer, the amount of rainfall and the amount of water humans take from the underground aquifer. Usually, the water in springs is very clear, but it can be discoloured due to the naturally occurring minerals in the ground. ## The Life of a River A river is a large natural stream of water that flows over land. Even though rivers hold only a tiny fraction of Earth's total water, they have always been essential to human civilization. Rivers carry freshwater to people, plants, and animals all across Earth. They provide people with a method of transport and water power. They also shape the land by carving out valleys and canyons. **Key word** - Upper course - Middle course - Lower course - Valley - Channel - Waterfall - Rapids - Gorge - Meander - Tributary - Floodplain - Delta - Estuary ### Rivers can be divided into three stages: #### The Upper Course Rain falling in highland areas flows downwards and collects in channels, forming a stream. As the stream continues to run downhill, it is joined by other streams and increases in size and speed. The point where two rivers join is called a confluence. Eventually the creek grows into a river. In its upper course the river flows rapidly. It cuts through the land and picks up soil and gravel. The moving water and the material it carries wear away even more rock and soil. Over thousands or millions of years, the river creates canyons and deep valleys in this way. #### The Middle Course As a river reaches its middle course, the fast-flowing water causes erosion, which makes it deeper and wider. The river erodes left and right, forming horse-shoe-like loops called meanders. In its middle course the river flows down gentler slopes. It gets larger and slower. Soil, gravel and sand begin to sink to the bottom. Some of this material builds up to form sandbars and islands. #### The Lower Course In the lower course, a river is in flatland and flows slowly. The force of the water is lower than in the other stages, so the river deposits all the bits of eroded land it has been carrying with it. In its lower course the river flows even more slowly. It drops still more solid material. Some material is carried all the way to the mouth-the place where the river enters the sea. This material may build up to form a piece of land called a delta.