18 terms

Topic 4b - River Processes and Pressures - Drainage Basin Hydrological Cycle and Hydrographs

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Hydrograph
A graph showing changes in a rivers discharge (line graph) and rainfall (bar graph) over time.
Rising limb
The increase in river discharge as the rainwater flows into the river.
Falling limb
The decrease in river discharge as the river returns to its normal level.
Lag time
This is a delay between peak rainfall (highest amount of rainfall) and peak discharge (highest volume of water in the river channel).
Peak discharge
This is the highest discharge in the period of time the graph records for.
Peak rainfall
The highest amount of rainfall received from the storm event.
Antecedent conditions
Conditions in a drainage basin in the period before a rainfall event, such as saturated or frozen ground.
Impermeable
Rocks that are impermeable, like clay, do not allow water to pass through them.
Permeable
Rocks that are permeable, like chalk, allow water to pass through them.
Infiltration
The process whereby water soaks into the soil and rock.
Percolation
Water flowing vertically through the soil and rocks below the surface.
Throughflow
Water flowing horizontally through the soil layer into the river.
Groundwater flow
Water flowing horizontally through the rock layer into the river.
Evaporation
Water turns from water droplets into water vapour due to heating from the sun and rises from the ground.
Transpiration
The release of water vapour through the stomata (pores) in plant's leaves
Interception
The process where vegetation catches rainfall on its leaves and branches.
Antecedent rainfall
Antecedent rainfall the amount of moisture already in the ground before a rainstorm
Bankful
the discharge or contents of a river which is just contained within its banks. This is when the speed, or velocity, of the river is at its greatest