Hydrographs Flashcards
What are the two types of hydrographs
Flash and steady
What is the discharge units
Cubic meters per second (cumecs)
What is baseflow
The normal day to day discharge of the river due to ground water seepage
What do the bars represent on a hydrograph?
Rainfall levels
The most influential factor on the shape of a hydrograph
Weather
Difference between a storm(flashy) hydrograph and a normal hydrograph
A storm hydrograph is over a much shorter period of time - hours or days vs weeks or months
What is lag time
The time difference between peak rainfall and peak discharge
What does a long lag-time represent
It has taken a while for the precipitation from the storm to enter the river (due to porous rock so less surface run-off, a lot of interception from vegetation, few tributaries etc…)
Rising Limb
The increase in river discharge as rainwater flows into the river following rainfall
Falling Limb
The decrease in river discharge as the river returns to its normal level
Drainage Basin
the area from which a single stream or river and its tributaries drains all of the water
Drainage basin shape influence
Circular drainage basin = flashy hydrograph as all points in the drainage basin are roughly equidistant so all the water will reach the river at the same time
Gradient of Drainage Basin
Higher gradient (steeper) have higher peak discharge and short lag time because water can travel faster downhill
High drainage density
Lots of tributaries
Short lag time and steep rising limb as water moves faster in tributaries than as ground water flow, through flow or surface run off
Soil/rock type
Non porous + impermeable rocks (i.e mudstone) = high discharge and short lag time b/c of low amounts of percolation and less groundwater/through flow
