Topic 1 - Rivers Flashcards
Precipitation
Input
Water falls from clouds (as drizzle, rain, sleet and snow) towards the surface
Interception
Store
The precipitation is caught and held for a short time by vegetation before it reaches the soil store. When there is more vegetation, more interception will occur and there is the potential for more evaporation, especially in the summer.
Stem Flow & Through Fall
Transfers
The movement of water from the interception store to the surface sore, either by flowing down the stem/beaches (stem flow) or dripping off the leaves (through fall)
Surface Storage
Store
Water is stored temporarily on the surface e.g. In puddles
Infiltration
Transfer
Water enters the soil from the surface store.
Overland flow / Surface runoff
Transfers
Water runs over the surface of the land following a rainstorm. This occurs when the soil either becomes saturated or because the rain intensity is too high and exceeds the infiltration capacity. It also occurs on impermeable surfaces.
Soil storage
Store
Water that has infiltrated is stored in the surface layers of the soil before experiencing either throughflow or percolation.
Throughflow
Transfer
Water moves downhill through the soil, close to and parallel with the surface, to the river
Percolation
Transfer
Water moves further down into the soil from the soil store to the groundwater store
Groundwater storage
Store
The permanent store of water in the lower layers of the soil and bedrock
Groundwater flow
Transfer
The movement of water from the groundwater store in the lower layers of the soil and the bedrock to the river.
Evaporation
Output
Water is changed into water vapour from various stores such as interception and surface storage. The main factor affecting the rate of evaporation is temperature
Transpiration
Output
Water vapour is taken from vegetation and plans into the atmosphere. This is affect by factors such as the vegetation type (e.g. deciduous trees lose their leaves in winter to reduce transpiration) and moisture availability.
What factors affect transfers and stores of matter in a drainage basin?
Vegetation Soil type Seasons Geology Urban Areas Relief How heavy the rain is
Abrasion
The most effective form of river erosion and occurs when the river uses its load to erode the bed and banks by scraping and scouring. It is particularly effective at times of higher discharge when the river has enough energy to transport larger particles.
Hydraulic Action
Occurs due to the physical force of the water against the bed and banks. On the outside bends to meanders, for instance, the currents push water into cracks, causing pressure that leads to erosion.
Solution / Corrosion
The dissolving of soluble materials in the bed and banks by weak acids in river water. A chemical reaction rather than a physical process and so is not dependent on the energy levels in the river. Most effective in rocks containing carbonates, such as limestone.
Attrition
Occurs when the load particles come into contact with other load particles and the bed and banks. As a result the rough edges are smoothed and the particles become smaller and more rounded.
Suspension
The smaller particles of clay, silt and sand can be carried along by the turbulence of the river.
Solution
The material eroded by corrosion is carried along and dissolved in the water m. This form of transportation can be significant in limestone areas, but tends to be less important in other areas
Saltation
The smaller bedload, such as pebbles and gravel, can be bounced along the riverbed by turbulence during times of higher discharge
Traction
The largest boulders in the river can be rolled along the riverbed during times of very high discharge
