Hillslope water cycle

Question 1

What is the hillslope water cycle affected by?

Answer 1

• natural and human factors
• changes in stores over short timescale
• magnitude of stores change in response to a variety of processes

Question 2

What are the factors affecting the hillslope water cycle?

Answer 2

• deforestation
• storm events
• seasonal change
• farming
• urbanisation
• water abstraction

Question 3

What is a river regime?

Answer 3

the variability in a rivers discharge throughout the course of the year, in response to precipitation, temperature, evapotranspiration and drainage basin characteristics

Question 4

How does deforestation lead to changes in the water cycle?

Answer 4

• removes water-absorbent forests which trap and transpire rainfall
• heavy machinery compacts soil decreasing infiltration
• less evapotranspiration/interception from tree canopy
• increased overland flow and throughflow - less friction from plants
• shorter lag time

extensive deforestation eg.in the Amazon leads to:
- reduced water vapour in the atmosphere due to decreased evapotranspiration - lower precipitation rates so river levels fall

Question 5

How do farming practices affect the water cycle?

Answer 5

• livestock lead to the trampling and compaction of soil - lower infiltration capacity
• crops - increase infiltration and evapotranspiration - crops are dormant in late autumn/winter so overland flow is high
• drainage ditches/soil drains - speeds up through flow
• groundwater abstraction of natural aquifers - more water in surface stores, water table drops and rivers dry out
• ploughing - aerates soil so increased infiltration capacity
• heavy machinery can compact soil - reduced infiltration

Question 6

How does water abstraction affect the water cycle?

Answer 6

• taking water from a ground source

over-abstraction can lead to:
- rivers drying up
- damage to wetland ecosystems
- sinking water tables

Question 7

How do extreme weather events lead to changes in the water cycle?

Answer 7

storms:
- saturated soil is eroded decreasing infiltration capacity
- wind damages vegetation leading to less transpiration and interception
- increased river discharge

drought:
- vegetation dries out or dies - wildfires, link to carbon cycle
- decreased river discharge
- abstraction of groundwater so water table drops

Question 8

How do seasonal changes lead to changes in the water cycle?

Answer 8

wet seasons -
- precipitation exceeds evapotranspiration leading to a water surplus
- groundwater stores are full and soil is saturated
- more surface runoff results in higher discharge levels
- water more likely to be locked up in cryosphere
- less evaporation due to decreased temperatures
- trees and vegetation die, less interception and transpiration

dry seasons - precipitation lower than evapotranspiration and groundwater stores are depleted . Water used by humans and plants is not replaced so water deficit

Question 9

What is river discharge?

Answer 9

the volume of water flowing through a river channel; measured at any given point in cubic metres per second.