Variations in Runoff and the Water Cycle Flashcards
What does is river discharge measured in?
Cumecs - m3/sec
Define peak discharge
River discharge is greatest - highest point on graph
Define lag time
Delay between peak rainfall and peak discharge.
Where is peak rising limb on a hydrograph?
The rise before peak discharge
Where is falling limb on a hydrograph?
Fall after peak discharge
What 4 things is runoff and hydrograph shape affected by?
- Size of drainage basin
- Shape of drainage basin
- Ground steepness
- Rock and soil type
How does size of drainage basin affect runoff + hydrograph?
Larger = holds more precipitation. Higher peak discharge vs smaller drainage basins.
Why do small drainage basins have shorter lag time?
Shorter distance for rain to travel before reaching river
How does shape of drainage basin affect runoff and hydrograph?
Circular = more flashy vs long, narrow basins. Circular = lots of water enters river at the same time
How does ground steepness affect runoff and hydrograph?
Water flows faster downhill, shortening lag time.
Less time for infiltration so more runoff.
How does rock and soil type affect runoff and hydrograph?
Impermeable rock = no infiltration, more runoff
More runoff = shorter lag time = higher peak discharge
How do storms affect water cycle?
Higher precipitation + peak discharge. Larger input causes flows to increase in size. Runoff increases as infiltration not fast enough.
How do seasonal changes affect the water cycle?
Summer = hotter Winter = cold so frozen stores increase Winter = less vegetation, less interception etc
How do farming practices affect the water cycle?
- Ploughing breaks soil surface, more infiltration
- Crops = less runoff as more interception
crops = more rain as more evapotranspiration - Livestock compact ground = more runoff
- Irrigation = more runoff / lower river levels if water extracted
How does land use affect the water cycle?
- Deforestation
Less interception, more runoff - Impermeable buildings
Less infiltration, more runoff
