water cycle - drainage basins Flashcards
what kind of system is a drainage basin
open system
local hydrological cycle
what is a drainage basin?
the area that supplies a river with its supply of water
what is another word used for drainage basins?
catchment area
how are drainage basins separated from one another?
by highland
what is the highland that separates drainage basins called?
the watershed
what is the main inout to the system?
precipitation
what is an interception store?
precipitation that falls on vegetation cover or man made cover is temporarily stored on the surfaces, it then either evaporated or absorbed by the surface or transmitted to groundwater
what is through fall?
precipitation that reaches the ground directly thorugh gaps in the vegetation cover in vegetation canopy and drips form leaves
when does trhoughfall occur?
when the canopy surface rainwater storage exceeds its storage capacity, so flaws form one store to then next
what is stem flow?
precipitation that reaches the ground by running down the stems
what is infiltration?
the downward movement of water from the surface into the soil
what is the rate of infiltration called?
the infiltration rate
what is infiltration controlled by?
gravity, capillary action and soil porosity
which factor of control is most important to infiltration?
soil porosity
what is soil porosity controlled by?
its texture, structure and organic content
why do storm events reduce infiltration?
filling of pores on surface reduces ability of capillary forces to move water into soil
clay absorbs water, reducing the size of pore spaces
large soil clumps break into smaller pieces which clog up pore spaces
what is soil storage?
the amount of water than is stored in the soil
what does soil consist of?
solid particles with pore spaces between them
what can pore spaces in soil be filled with?
air but also water
what is vegetation storage?
when plants take water form the soil and store it in its structure
how do plants lose water and where from?
transpiration into the atmosphere through stomata on their leaves
what is infiltration capacity?
what is does it result in?
when rainfall intensity is greater than the rate of infiltration rate
saturation of soil
when infiltration capacity has been reached what happens to the water?
water builds up on the surface, this is known as surface storage
what is a form of surface storage?
puddles
where is surface storage more common?
man made areas
rare in natural environments
when does water build up on the surface?
after intense long rainfall, impermeable surface
how is water lost from drainage basin by surface storage?
this water evaporates into the atmosphere
what is evapotranspiration/why is it used?
it is difficult to separate evaporation and transpiration, so the total amount lost in both ways is referred to as evapotranspiration
what is through flow?
movement of water down slope through sub soil, carries on until reaches nearest channel
what is overland flow?
when surface storages have reached max capacity so water begins to travel downward over the surface
which is faster overland or through flow?
overland flow
how can though flow be made quicker?
the more vegetation available, the faster it is as movement is aimed by root channels in the soil
what is percolation?
downward movement of rock under the soil surface
after infiltration has occurred what happens?
water moves vertically downwards to unsaturated rocks, known as percolation
what is groundwater?
when water is held in pore spaces in rocks
what is groundwater flow?
when water can move vertically and laterally
what are aquifers?
very porous rocks that can store a large amount of water
what can groundwater flow help to do?
feed river through periods of drought
what do all these movements and stores make up?
the drainage basin hydrological cycle
where do all the flows in a drainage basin lead to?
rivers
where does water move the fastest?
on the surface
what type of soil does water move slowest in?
clay, retains water, can evaporate before it moves horizontally
once water reaches below soil what happens?
the rate of movement slows down
how long can groundwater be stored for?
a millennia
what is channel storage?
water stored in rivers, although not for very long as it moves to sea
what are the types of stores in drainage basin?
- interception
- vegegtation
- groundwater
- channel
- soil
- surface storage
what are the types of flows in drainage basin?
infiltration percolation baseflow interflow channel flow evaporation transpiration throughfall stem flow overland flow ground water flow
