Geography- Rivers

Hydrological Cycle

The global circulation of water between the atmosphere, lithosphere, biosphere, and hydrosphere.

Hydrological Cycle Order

Precipitation ⇥ Interception ⇥ Stem flow/Drip tip ⇥ Surface runoff ⇥ Infiltration ⇥ Throughflow ⇥ Percolation ⇥ Groundwater flow ⇥ Evapotranspiration ⇥ Condensation

Precipitation

Any form of water that falls from clouds and reaches Earth's surface.

Infiltration/Percolation

Downward movement of water through soil and rock due to gravity.

Throughflow

The flow of water between the ground surface and the top of the groundwater store; moves slowly under the influence of gravity until it reaches a body of water.

Groundwater Flow

Flow of water through the aquifer until it reaches the river.

Drainage Basin

An area of land drained by a river and its tributaries.

Features of a Drainage Basin

Main channel ⇥ Confluence ⇥ Tributaries ⇥ Watershed ⇥ Estuary ⇥ Source

Factors Affecting the Speed of River Discharge

Rock type ⇥ Human land use ⇥ Relief ⇥ External climate

Factors Affecting the Amount of Discharge

Size of basin ⇥ Vegetation ⇥ Rainfall ⇥ Land saturation ⇥ Steepness ⇥ Human land use (urbanisation)

River Processes

Erosion ⇥ Transportation ⇥ Deposition

Weathering

The breaking down or dissolving of rocks in situ.

Types of Weathering

Physical ⇥ Chemical ⇥ Biological

Physical Weathering

Caused by temperature or climate changes.

Biological Weathering

Roots of plants grow in the cracks of a rock and split it.

Chemical Weathering

Weathering by acid rain, causing decay.

Mass Movement

The bulk movement of material due to gravitational pull.

Types of Mass Movement

Rockfall ⇥ Slumping ⇥ Creeping

Rockfall

Large material falling quickly.

Slumping

Material slides along bedding planes.

Creeping

Soil moves slowly.

Erosion

Wearing away and removal of rocks by the action of water, wind, or ice.

Abrasion (Sandpaper Action)

Material carried in the river scrapes and wears away at the river bed, causing the river to widen and deepen.

Attrition

Rocks in the flow of the water knock against each other, causing rounder and smaller loads.

Hydraulic Action

Water is forced into cracks in the bed, and pressure expands the cracks further.

Solution (Erosion)

River water reacts with alkaline substances in the bed and banks, dissolving them.

Transportation

The movement of material downstream. The larger the material, the more energy the river needs to carry it.

Types of Transport

Traction ⇥ Solution ⇥ Suspension ⇥ Saltation

Traction

Heavy material is rolled along the river bed.

Saltation

Small material bounces in small hops along the river bed.

Suspension

Fine loads carried along by the river flow.

Solution (Transport)

Soluble material dissolved in river water and transported downstream.

Deposition

Occurs when the river does not have enough energy to carry the material any further.

Factors Affecting Deposition

Reduction of gradient ⇥ Reduction in volume of water ⇥ Increased friction from bed and banks

Upper Course River Landforms

V-shaped valleys ⇥ Interlocking spurs ⇥ Waterfalls and gorges

Characteristics of Upper Course Landforms

Narrow and shallow ⇥ Vertical erosion

Features of a Waterfall

Cap rock ⇥ Overhang ⇥ Less resistant rock ⇥ Scree ⇥ Plunge pool ⇥ Gorge

Middle Course River Landforms

Meanders ⇥ Levees ⇥ Oxbow lakes

Characteristics of Middle Course Landforms

Less vertical erosion, more lateral ⇥ Deeper and wider ⇥ Deposition on inside bend

HIC Water Usage

70% agricultural ⇥ 20% industrial ⇥ 10% domestic

Virtual Water

Water that is not directly consumed but is used to produce food and other products.

Water Pollution from Farms

Fertiliser leaching ⇥ Eutrophication ⇥ Increased bacterial growth and deoxygenation

Water Pollution from Industries

Chemical run-off ⇥ Oil spillage ⇥ Factory wastes ⇥ Offshore dumping of sewage sludge

Water Pollution from Other Sources

Domestic untreated sewage ⇥ Chlorinated swimming pools

Water Management

Collection ⇥ Purification ⇥ Delivery

Water Purification Methods

Filtration and sedimentation ⇥ Bacterial disinfection ⇥ Chlorination ⇥ Aeration

Three Gorges Dam Facts

Built in 2009 ⇥ Yangtze River ⇥ 185 m high ⇥ 2 km wide ⇥ 600 km from Shanghai to Chongqing ⇥ Reduced flooding risk

Three Gorges Dam - Pros

Generates 6% of China's energy ⇥ Flood control for Wuhan ⇥ Irrigation ⇥ Navigation ⇥ Tourism

Three Gorges Dam - Cons

Flooded 13 cities, 140 towns, 1,350 villages ⇥ 1.4 million relocated ⇥ Temples destroyed ⇥ Industrial pollution ⇥ 3,000 earthquakes ⇥ Yangtze dolphin extinction ⇥ $131.3 million cost

Natural Causes of Flooding

Prolonged rainfall ⇥ Rapid snowmelt ⇥ Impermeable rock ⇥ Steep relief ⇥ Vegetation

Human Causes of Flooding

Urbanisation ⇥ Deforestation ⇥ Agriculture ⇥ Soil erosion ⇥ Climate change

Environmental Effects of Flooding

Loss of wildlife ⇥ Landslides ⇥ Destroyed vegetation ⇥ Spread of pollutants

Flooding Effects on Humans

Waterborne diseases ⇥ Injuries and deaths ⇥ Property loss ⇥ Infrastructure destruction ⇥ Contamination ⇥ Rebuilding costs

Hard Engineering for Flooding

Dams ⇥ Levees ⇥ Channelisation ⇥ Flood barriers

Pros of Dams

Prevent downstream flooding ⇥ Multipurpose

Cons of Dams

Expensive ⇥ Destructive ⇥ Traps sediment - dam failure risk

Pros of Levees

Floodplain still usable

Cons of Levees

Expensive ⇥ Breaching risk

Pros of Channelisation

Increases velocity ⇥ Reduces friction

Cons of Channelisation

Ecosystem disruption ⇥ Flooding downstream

Soft Engineering for Flooding

Land use planning ⇥ Afforestation