rivers Flashcards
inputs into a drainage basin
tributaries
precipitation
transfers in a drainage basin
infiltration stem flow overland flow through flow groundwater flow percolation
outputs of a drainage basin
transpiration
evapotranspiration
storage in a drainage basin
surface stores
groundwater stores
soil water
water balance
difference between inputs and outputs and the subsequent change in storage
equation for water balance
precipitation = total runoff + evapotranspiration +/- storage (soil/rock)
if precipitation exceeds runoff and evapotranspiration there is a..
positive water balance
there is a negative water balance when..
runoff and evapotranspiration exceed precipitation
soil moisture budget
the change in amount water stored in the soil throughout the year
levels of evapotranspiration are highest in what season? why?
spring and summer, warmer temperatures lead to more plant growth and therefore more evaporation and transpiration
discharge
the amount of water in a river flowing past a particular point at a given time (expressed in cumecs)
bankfull
the amount a river channel can hold without flooding
lag time
time between peak rainfall and peak discharge
peak discharge
the point on a flood hydrography where river discharge is at its greatest
base flow
the normal day-to-day discharge of a river; its the consequence of slow moving soil throughflow and groundwater seeping into channel
discharge calculation
cross section area volume x speed
rising limb of hydrograph
how quickly the river responds to a storm
falling limb of hydrograph
how quickly the river returns to normal
how deforestation affects river flows
deforestation means theres less vegetation to absorb precipitation so a river will flood more easily (creates a flashy hydrograph)
how afforestation affects drainage basin
more interception of precipitation
more evapotranspiration
less flooding
how rock type impacts drainage basin
permeable = less flooding impermeable = quicker surface flow, more flooding
how do slope angles impact flooding
steeper slopes = more runoff and surface flow so river floods more quickly
percolation
movement of water down through ground
stem flow
water runs down stems of plants
ground water storage
water thats stored deep in the ground in bedrock
