Rivers - Hydrographs And River Regime

Question 1

Storm hydrograph

Answer 1

• Shows how a river’s discharge changes in response to a rainfall event
• shape of hydrograph is influenced by a range of physical and human factors

Question 2

Lag time

Answer 2

The delay/ time between peak rainfall and peak discharge

Question 3

Base flow

Answer 3

Normal discharge of the river

Question 4

Storm flow

Answer 4

Additional discharge of the river as a result of the rainstorm

Question 5

Factors that affect river regime

Answer 5

1. Amount and intensity of the rain - -> Heavy rain will not sink into the ground. It becomes surface run off quickly reach the river
2. Temperatures -
   - > if below freezing, precipitation will be in form of snow, taking weeks to melt
3. Slope gradient -
   -> Steep slopes cause rapid surface run off
   Gentle slopes lead to more infiltration, hence delaying it from reaching the river
4. Rock type -
   - > Impermeable rock speed up run off since there is less infiltration
   - > Permeable rock allow infiltration and percolation of water into the bedrock, this slows delivery of water to the river
5. Vegetation and land use -
   - > Trees and other plants causes interception to increase and delay the rain reaching the ground
   - > Bare soil and rock speed up run off and reduce time lag
   - > Urban areas under tarmac and concrete increase surface runoff and decrease infiltration
   - > rural areas increase infiltration and percolation and decrease surface runoff
6. Human intervention -
   - > dams and reservoirs are forms of intervention in river regimes. They hold back discharge, reducing flood downstream. They can be controlled by opening and closing sluice gates
   - > Increase of abstraction leads to decrease in river discharge and stability of ground

Question 6

River regime

Answer 6

The variations that a river experiences throughout a year, plotted on a graph, usually reflect climate, geology and land use of the area