H Geography - Physical Unit - Hydrosphere - Hydrographs

What can you talk about in a hydrograph

In a hydrograph, you can talk about;

• Lag time

• Discharge before rising limb

• Rising limb

• Peak discharge

• Recession limb

• Discharge after recession limb

What should you use in a hydrograph?

You should use cumecs

What factors can have an impact on a hydrograph?

• Time rainfall began

• Presence of vegetation

• How full the soil storage is

• Number of tributaries

• Size of catchment area

• Slope of catchment area

What are reasons for change in a hydrograph?

• A lack of vegetation means less rain is intercepted so more will quickly reach the river

• The river discharge level may rise because soil storage has been exceeded, meaning that rain travels as surface flow and reaches the river quickly

• There may be a high number of tributaries transporting water to the channel quickly

• There may be a small catchment area meaning less travel time to the main channel. The catchment area may be steeply sloping leading to faster initial overland flow

• The area may have impermeable surfaces leading to overland flow

• There may be drainage pipes transporting water quickly

• The initial rainfall may have been intercepted by vegetation

• Likely a rural area with a lack of tarmac increasing infiltration

• There may be a low number of tributaries transporting water to the channel slowly

• The catchment area may be gently sloping leading to slower initial overland flow to the channel

• It may be a large catchment area meaning more travel time to the main channel

• There may be porous soils/peaty soils increasing soil storage

• There may be permeable rock allowing for increased groundwater storage

• The river rises because soil storage has been exceeded.