Rivers

THE HYDROLOGICAL CYCLE

• Water evaporates - it turns from a liquid to a gas
• Wind blows the water vapour inland, where it rises and cools
• When the water vapour condenses, a cloud is formed
• The droplets of water become bigger and heavier, until they fall to the ground as precipitation
• Some of the precipitation flows over the land into rivers and back into the sea
• Some water soaks into the ground and slowly seeps into rivers
• Some water is absorbed by plant roots.  Some of this water escapes from the surface of leaves in a process called transpiration

RIVER BASIN TERMINOLOGY

• The source - the place where the river starts
• Tributary - a small river joining the main one
• Confluence - the place where a river or tributaries join
• Floodplain - the area of alluvium on the valley floor
• Watershed - the highland rim of a drainage basin
• Estuary - the place where the river widens as it meets the sea
• Drainage basin - a lowland area where all the precipitation that falls will eventually work its way into one river system
• Meander - a bend or loop in the river

Inputs of the hydrological cycle:

• Precipitation - condensed droplets of water falling from clouds

Outputs of the hydrological cycle:

• Transpiration - where water escpapes from the surface of leaves
• Evaporation - where water goes from a liquid to a gas
• Water returned to sea through river channel

Storages of the hydrological cycle:

• Interception - when precipitation is caught by plants
• Surface storage - when precipitation is stored on the suface of the ground
• Soil moisture storage - when precipitation is stored in the soil
• Groundwater - water stored in rocks beneath the soil

Transfers of the hydrological cycle:

• Stemflow - when water moves through the xylem of the plant
• Infiltration - when water movers vertically downwards through the soil
• Percolation - when water moves vertically downwards from the soil into rocks
• Surface run-off - when water moves horizontally across the surface of the ground
• Throughflow - when water moves horizontally through the soil
• Groundwater flow - when water moves horizontally through the rocks beneath the soil
• River channel flow - when water flows in the river channel

PROCESSES OF EROSION

• Hydraulic action - when the force of the water dislodges parts of the river bed and forces air into cracks in the river bed
• Corrasion - where the load of the river erodes the river bed
• Attrition - where the particles carried with the river collide with each other and make each other rounder and smoother
• Solution - when the river is slightly acidic and erodes the river bed chemically

PROCESSES OF TRANSPORT

• Traction - when large boulders are pushed along the river bed by the force of the water
• Saltation - when small pebbles bounce along the river bed, carried by the force of the water
• Suspension - when fine particles like silt are carried along by the river
• Solution - when soluble materials dissolve in the water…