1.1.2 The drainage basin system Flashcards
What scale is the drainage basin system
Local
What type of system is the drainage basin system
Open
Inputs
Precipitation - rain, snow and hail
Types of rainfall
Convectional, relief and frontal warm
Convectional Rainfall
Sun heats land, warm air rises, condenses at higher altitudes and falls
Relief rainfall
Warm air is forced upward by a barrier such as mountains , causing it to condense at higher altitudes and fall as rain.
Frontal Warm Rainfall
Warm air rises over cool air when two bodies of air at different temperatures meet, because the warm air is less dense and therefore lighter. It condenses at higher
altitudes and falls as rain.
Outputs
Evapotranspiration and Streamflow
Evapotranspiration
Compromised of evaporation and transpiration. Evaporation occurs when water is heated by the sun, causing it to become a gas and rise into the atmosphere. Transpiration occurs in plants when they respire through their leaves, releasing water they absorb through their roots, which then evaporates due to heating by the sun.
Streamflow (as output)
All water that enters a drainage basin will either leave through the atmosphere, or through streams which drain the basin. These may flow as tributaries into other rivers or directly into lakes and oceans.
Flows (7)
Infiltration, Percolation, Throughflow, Surface runoff (overland flow), Groundwater flow, Streamflow, Stemflow
Infiltration (f)
This is the process of water moving from above ground into the soil. - Moderate/Fast
Percolation (f)
Water moves from the ground or soil into porous rock or rock fractures. - Slow
Throughflow (f)
Water moves through the soil and into streams or rivers. Speed of flow is dependent on the type of soil. - Moderate/Fast
Surface runoff (f)
Water flows above the ground, as sheetflow, or in rills - Fast
Sheetflow
lots of water flowing over a large area
Rills
small channels similar to streams, that are unlikely to carry water during periods where there is not any rainfall
Groundwater flow (f)
Water moves through the rocks. Ensures that there is water in rivers, even after long period of dry weather. - Usually slow but variable
Streamflow (f)
Water that moves through established channels - Fast
Stemflow (f)
Flow of water that has been intercepted by plants or trees, down a stem, leaf, branch or other part of a plant - Fast.
Stores (4)
Soil water, groundwater, River channel, Surface storage
Soil water (s)
Water stored in the soil which is utilised by plants - Mid-term
Groundwater (s)
Water that is stored in the pore spaces of rock - Long-term
River Channel (s)
Water that is stored in a river - Short-term
Interception (s)
Water intercepted by plants on their branches and leaves before reaching the ground - Short-term
Surface Storage (s)
Water stored in puddles, ponds, lakes etc. - Variable
water table
upper level at which the pore spaces and fractures in the ground become saturated.
Use of water table by researchers
to assess drought conditions, health of wetland systems, success of forest restoration programmes etc.
how quickly infiltration occurs.
Infiltration capacity
overland flow will occur
If precipitation falls at a greater rate than the infiltration capacity
Percolation rate
is dependent on the fractures that may be present in the rock and the permeability of the rock
Infiltration capacity can be increased by
Grass crops and tree roots create passages for water to flow through from the surface into the soil
Field capacity
Clay soils with a high field capacity and smaller pore spaces have a slower flow rate. Sandy soils drain quickly because they have a lower field capacity, larger pore spaces and natural channels from animals such as worms. Some sports fields have sandy soils, to reduce the chance of waterlogged pitches, but this may also increase the flood risk elsewhere
Area with faster groundwater flow
Jointed rocks such as limestone in Karst environments where there are many underground streams and caves , may transfer water very rapidly
