Term
The hydrological cycle (also known as the water cycle)
Seas and oceans contain 97% of the world's water supply, and ice holds 2%. That leaves just 1 per cent of the world's water as fresh water on land or in the air. This water is recycled again and again through the process of evaporation, condensation and water transfers such as surface run-off. |
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Definition
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Term
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Definition
Drainage basin - the area of land drained by a river.
Catchment area - the area within the drainage basin.
Watershed - the edge of highland surrounding a drainage basin. It marks the boundary between two drainage basins.
Source - The beginning or start of a river.
Tributary - a stream or smaller river which joins a larger stream or river. |
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Definition
As a river flows down steep slopes the water performs vertical erosion. This form of erosion cuts down towards the river bed and carves out steep-sided V-shaped valleys.
The discharge (amount of water flowing) will increase as the river approaches the sea. |
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Definition
| Near the source of a river there is more vertical erosion as the river flows downhill, using its energy to overcome friction (A).As the river approaches the mouth, velocity and energy increase due to increased discharge. The river performs more lateral erosion making the channel wider, and smoother (B) and (C). As a result there is less turbulence and friction, making the flow of water more efficient. |
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Term
River Processes:
Hydraulic action - the force of the river against the banks can cause air to be trapped in cracks and crevices. The pressure weakens the banks and gradually wears it away.
Solution - soluble particles are dissolved into the river
Attrition - rocks being carried by the river smash together and break into smaller, smoother and rounder particles.
Abrasion - rocks carried along by the river wear down the river bed and banks. |
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Definition
Transportation Processes:
Solution - minerals are dissolved in the water and carried along in solution.
Suspension - fine light material is carried along in the water
Saltation - small pebbles and stones are bounced along the river bed.
Traction - large boulders and rocks are rolled along the river bed.
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Term
Deposition:
Deposition may take place when a river enters an area of shallow water or when the volume of water decreases - for example, after a flood or during times of drought.
Deposition is common towards the end of a river's journey, at the mouth.
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Definition
River Landforms:
UPPER - narrow, slower
As the river erodes the landscape in the upper course, it winds and bends to avoid areas of hard rock. This creates interlocking spurs, which look a bit like the interlocking parts of a zip.
When a river runs over alternating layers of hard and soft rock, rapids and waterfalls may form.
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Term
MIDDLE - more energy and volume
As the river erodes laterally, to the right side then the left side, it forms large bends, and then horseshoe-like loops called meanders.
Over time the horseshoe become tighter, until the ends become very close together. As the river breaks through, eg during a flood when the river has a higher discharge and more energy, and the ends join, the loop is cut-off from the main channel. The cut-off loop is called an oxbow lake. |
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Definition
LOWER - high volume, deep, wide, deposition takes place here mostly as the water velocity is slow
Deltas and floodplains are found here
Floodplain - is the area around a river that is covered in times of flood (generally a well fertile area of land, where a lot of agriculture is present)
Delta - formed when the river can deposit it's material faster than the sea can remove it |
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Term
Flooding - generally caused by heavy rain
Factors that may encourage flooding:
Steep-sided channels (causes fast surface run-off),
a lack of vegetation or woodland (can't soak up the water),
a drainage basin consisting of mainly impermeable rock (means that the water will run faster over the surface) |
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Definition
Impact of flooding
- Loss of homes and possessions
- Loss of jobs
- LEDS are usually more affected, as most of their income are from farming communities, and a flood may ruin their crops (LEDS also don't have the flooding preventions that MEDS have)
HOWEVER; floods make the land more fertile, and some citizens of LEDS may rely on flooding of nearby land to provide vegatation for income, and also food |
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Term
River Management:
Hard-engineering:
Dam constructions: used to control the amount of discharge. This water can then be used to generate hydroelectric power or for recreation purposes. HOWEVER, dams can be very expensive to build and also maintain
River engineering: used to make the river wider or deeper, in order for it to be able to hold more water. HOWEVER, altering the river may lead to flooding downstream
Governments and developers often favour large hard engineering options, such as dam building. Building a dam and a reservoir can generate income. |
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Definition
Soft engineering:
Afforestation: Trees are planted near to the river. This means greater interception of rainwater and lower river discharge. This is a relatively low cost option, which enhances the environmental quality of the drainage basin.
Managed flooding: The river is allowed to flood naturally in places, to prevent flooding in other areas - for example, near settlements. |
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Definition
Industrial Use:
Industries in MEDCs can be on a large scale, and so demand a lot of water.
LEDCs have smaller scale cottage industries, and they demand less water in the production of items.
Domestic Use:
In MEDCs there are a lot of facilities which demand water use such as showers, baths, washing machines and swimming pools.
In LEDCs many people do not have access to piped water and so use it more sparingly (water may be brought to the home from a well or stream)
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Factors that can trigger a drought: (human activities)
Constructing a dam - may cause a drought downstream by severely reducing the flow of water, whilst providing electricity and jobs
Widespread deforestation - reduces the soil's ability to hold water, which dries out the ground |
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Definition
Effects of a drought:
Pressure - if people migrate to other countries during a drought, it can put pressure on resources in neighbouring countries 20th century droughts in Africa
Diseases spread quicker, causes hunger, thirst and death
MEDC's also suffer from droughts badly, - UK hose-pipe ban was introduced in 2006, as people died from a lack of water resources |
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