variations in run off and water cycle Flashcards
what do hydrograph show?
shows a rivers discharge over a period of time
what is river discharge?
the volume of water that flows in a rover per second
what is river discharge measured in?
cumecs
cubic metres 3 per second
what increases a rivers discharge?
high levels of surface runoff as more water is entering the river increasing its volume
what do flood hydrographs show?
river discharge around the time of a storm event
cover s short time period
what is peak discharge? SH
the highest point on the graph when discharge is at its greatest
what is lag time? SH
the delay between peak discharge and peak rainfall
why does lag time occur?
it takes time for rainwater to flow into the river
if lag time is shorter what does this mean?
that peak discharge is likely to be higher as to be higher as there is a greater amount of water flowing into the river in a short amount of time
what is the rising limb? SH
this is the part of the graph that leads up to peak discharge
if it is steeper it indicates that there is a large amount of water entering in a short time
what is the falling limb?
after peak discharge
less water so discharge is decreasing
what is baneful discharge?
this is when discharge reaches the point in which water reaches the top of the river
what is a flashy hydrograph?
symmetrical falling and rising limb
not much storage and rapid runoff
what factors are runoff and hydrography shape affected by?
- size of basin
- shape of basin
- groud steepness
- rock and soil tye
how does size of basin affect runoff and hydrography shape?
a larger basin can catch more water meaning peak discharge is likely to be greater
a smaller basin is likely to have a higher lag time as don’t have to travel as far
what natural factors are run off, hydrographs and water cycle affected by?
storms and precipitation
seasonal changes and vegetation
how does vegetation affect water cycles?
deciduous trees (lose leaves) more vegetation can reduce peak discharge and runoff as lost through transpiration and uptake
what are human activities that affect water cycle?
famring practises
land use change
water abstraction
how do framing practices affect water cycle?
it can affect infiltration
ploughing can break up surface so more water can infiltrate reducing runoff
crops increase interception reducing runoff and more evapotranspiration
livestock trample and compact the soil decreasing infiltration
irrigation increase runoff, groundwater can fall if it is extracted for irrigation
how does land use change affect water cycle?
deforestation - not intercepted, increase infiltration, if plants removed then the dead material cannot hold water which usually reduces infiltration
construction - impermeable layer makes flooding more likely
how does water abstraction affect water cycle?
if more water is abstracted it reduces the amount of water in lakes, resoivois and groundwater
it can lower the water table meaning that stores can become depleted
groundwater will not be able to recharge rivers and water table
