eq1 - physical factors affecting drainage basin Flashcards
what is the drainage basin
an open system that is an area of land that is drained by a river and its tributaries
what are the 3 types of inputs affecting the hydrological cycle
- convectional- ground warms causing evaportation which casues intense weather
- orographic- warm moist air forced to rise overupland areas causing rainfall
- frontal- moist air meets colder polar ari forming rain
what are the physical factors affceting the drainage basin
- interception
- infiltration
- percolstion
- direct runoff
- saturated overland flow
- infiltration excess overland flow
- growndwater flow
what is intercerption
raindrops are prevented from from falling directly onto the ground surface due to the layer of vegetation
vegetation prevents the rate of precipitation
what is infiltration
where water is absorbed
what is percolstion
similar to inflitration however involves deeper transfer of water into permeble rock
what is direct runoff
water flowing over the surface of the ground
what is saturated overland flow
occurs when water accumulates in the soil and cannot absorb any more water. This causes water to run off the surface.
what is infiltration excess overland flow
occurs when rainfall intensity exceeds
the infiltration capacity so excess water flows over the ground surface
what are the 3 physical factors affceting the driange basin outputs
- evaporation
- transpiration
- channel flow
4.
what is channel flow
water that has been collected to flow in a river or stream
what
what is evapotranspiration
The total amount water removes from the drainage basin by the process of transpiration and evaporation
name the 5 factors whihc determine the importance of the flows outputs and inputs
- climate
- soils
- veg
- geology
- relief
vegations contibution
transpiration increases deu to more vegeation
vegetaion with a low albedo wiill reflect will absorb more solar rad meaing increased evaporation
climates contribution
– influences
amount of rainfall and
vegetation growth.
soils contribution
nfluences rate of infiltration
and throughflow.
geologys contibution
affects
percolation and
groundwater flow
relief conribution
➢ Relief – steeper gradients
of land will encourage faster
rates of surface runoff
name the 4 human disruptions of the drainage basin
cloud seeding
urbanisation
dam construction
groundwater abstraction
what is cloud seeding
this is the attempt to change the amount or type of preciptation by dispersing substances into the air.
what is urbanisationan and what does it create
urbanisation creates impermeable surfaces that reduce infiltration adn increase surface runoff
what are the increases and decreases of dam construction
dams increase surface water stores
adn evaporatioon
and reduce downstream river discharge
what
what is groundwater abstarction
groundwater is abstacted from some aquifers faster than it is replaced
removing water from an underground source
h
what is a water budget
shows the annual balance bewteen inputs(precip)and outputs(evapotranspiration, channel flow).
what is a river regime
the annual variation in the dischareg of a river
what is the watershed
boundary of the drainage basin
how has defroestation affcted the amazonian river
-has lowered humidity’s
-less precipitation
-more surface runoff
-more evaporation, less transpiration
-more soil erosion and slit being fed into the rivers.
decribe the features fo the amazonian rainforest
- 6308 km long
- drains a basin of nearly 6 million km2
- humid tropical climate
- peak discharge in may, lowest in september
what is the discharge of a river
the volume of water flowing through a river channel
describe the features of the yukon river
- 3540 km long
2.drainage basin area of 850,000
3.tundra climate
4.peak dischareg in may, lowest in decemeber
5.
describe the features of the river nile
- changed deu to the aswan dam
- flow was reduced by 65%
- flood peaks in september
4.
what does a stormhydrograph show
variations in rivers discharge at a specific point over a short period of time
what are the main features of a storm hydrograph
-the rising limb
-peak discharge
-lag time
-falling/ recessional limb
-base flow
rising limb
where the discharge starts to rise after the rainfall starts
peak discharge
reached after the peak rainfall
-its the greatest vol of water-flooding may occur
base flow
where the rivers dischareg eventually returns to normal
lag time
the interval between the peak rainfall and the peak discharge
falling limb
once the rainfall starts to decrease so deos the discharge
what the two ways a storm hydrograph can be described
flashy and subdeud
what is a flashy hydrograph
very steep limbs(rising)
1)high peak discharge
2) short lag time
what is a subdued hydrograph
hydrographs with gently inclined limbs
1)low peak discharge
2)long lag time
de
describe the drainage basin size of a flashy and subdued hydrograph
f=small basin
s=large basin
describe the drainage basin shape of a flashy and subdued hydrograph
describe the drainage basin shape of a flashy and subdued hydrograph
f-circular basin
s-enlongated basin
describe the drainage basin relief of a flashy and subdued hydrograph
f-steep slope
s-gentle slope
describe the soil type of a flashy and subdued hydrograph
f-clay soils, thin, low porosity-water infiltrates slowly
s-sandy soils and thick soils-high porotity-more infiltration
describe the rock type of a flashy and subdued hydrograph
f-imperable rock-increases surfaec runoff
s-permeablel rocks
describe the rock type of a flashy and subdued hydrograph
f-imperable rock -increases surface runoff
s-permable rock-
describe the drainage density of a flashy and subdued hydrograph
f-high drainage density
s-low drainage density
describe the natural vegetation of a flashy and subdued hydrograph
f-thin grass-intercepts little water
s-forests and woodland-intercepts water-high evaporation rates
describe the land use of a flashy and subdued hydrograph
f-urban surfaces-harder surfaces-carry water more rapdily to water sources
s-rural-vegetated surfaces-intercept water-allow interception-travel slower to water sources
describe the preciptation intensity of a flashy and subdued hydrograph
f-high intensisty-
s-low intensity
describe the preciptation duration of a flashy and subdued hydrograph
f-prolonged-water table rises and soil becomes saturated
s-short duration-
describe the snowfall of a flashy and subdued hydrograph
f-fast snowmelt
s-slow snowmelt
describe the evapotranspiration of a flashy and subdued hydrograph
f-low rates-fewer losses from the drainage basin
s-high rates- high evapotranspiration losses will reduce discharge into the river channel
