River Discharge Flashcards
What is river discharge?
The volume of water flowing in a river per second.
What is the volume of water measured in?
Cumecs - cubic metres per second.
What do hydrographs show?
How the discharge at a certain point in a river changes over time.
What shows the changes in discharge around the time of a storm?
Storm hydrographs.
What is the peak discharge?
Highest discharge in the period of time you’re looking at.
What is lag time?
Delay between peak rainfall and peak discharge.
What is rising limb?
Increase in river discharge as rainwater flows into river.
What is falling limb?
Decrease in river discharge as river returns to normal level.
Why does lag time happen?
Most rainwater doesn’t land directly in the river channel.
Delay as rainwater gets to channel.
How does the water get into the river channel?
Flowing quickly over land.
Soaking into the ground and flowing slowly underground.
What is the name when water quickly travels over land?
Surface runoff.
Runoff.
What is the name when water soaks into the ground?
Infiltration.
River discharge is affected by…
Different factors.
More water that flows as surface runoff…
The shorter the lag time.
Shorter the lag time means…
Discharge will increase as more water gets to the channel in shorter space of time.
Name the 6 different factors river discharge is affected by?
Amount/type of rainfall. Temp. Previous weather conditions. Rock type. Land use. Relief.
Lots of rain and short, heavy periods of rainfall means…
More surface runoff.
Lag time decreased so…
Discharge increased.
What weather conditions result in hard ground?
Hot, dry.
Cold, freezing.
Hot, dry.
and
Cold, freezing weather increases what?
Increases surface runoff.
Lag time is decreased so….
Discharge increases.
After lots of rain soil can become what?
Saturated.
What does saturated mean?
Unable to absorb any more water.
If the soil is saturated what will happen?
Rainwater won’t be able to infiltrate into soil.
If less rain is able to infiltrate what will happen?
Surface runoff increases.
Water can infiltrate through…
Pore spaces in permeable rock.
Flow along cracks in previous rocks.
If rock can infiltrate through pore spaces and along cracks in rocks it means…
Isn’t much surface runoff.
Water can’t infiltrate through…
Impermeable rocks.
If rocks can’t infiltrate through impermeable rocks then what does it mean?
Lot of surface runoff.
What do urban areas have?
Drainage systems.
What are urban areas covered in?
Impermeable material.
Concrete.
Define relief
How the height of the land changes.
What occurs on steep slopes?
Lots of surface runoff.
When there’s a lot of surface runoff there is decrease in…
Lag time.
