The Water Cycle Flashcards
(26 cards)
What is the global hydrological cycle?
A closed system where water moves between stores (oceans, ice, lakes, atmosphere) through processes like evaporation, precipitation, and runoff.
What are the 4 major global water stores?
• Oceans (96.5%)
• Cryosphere (Glaciers/Ice caps - 68.8% of freshwater)
• Groundwater (30% of freshwater)
• Surface Water (1.2% of freshwater)
What are the 7 key processes in the water cycle?
Precipitation, evaporation, transpiration, infiltration, percolation, runoff and condensation.
Why is a drainage basin an open system?
It consists of inputs, transfers and outputs in which water can leave the system and new water can enter through precipitation
What are the 3 main types of precipitation affecting drainage basins?
• Orographic: Air rises over mountains, cools, and rains.
• Frontal: Warm and cold air masses meet, causing rain.
• Convectional: Heat causes rising moist air, leading to rain.
What are the 3 outputs in a drainage basin?
Evaporation, transpiration, and channel flow.
What are the 6 key flows in a drainage basin?
Infiltration, interception, surface runoff, throughflow, percolation, groundwater flow.
What is the water balance equation?
P = Q + E ± S, where
• P = Precipitation
• Q = Discharge
• E = Evapotranspiration
• S = Changes in storage
What 5 factors affect the water budget?
Climate, seasonal variations, deforestation, irrigation & dam construction
What 4 human factors increase flood risk?
• Deforestation: Less interception, more surface runoff.
• Urbanisation: Impermeable surfaces increase runoff.
• Agriculture: Soil erosion reduces river capacity.
• Poor River Management: Hard engineering can worsen flooding.
What 4 physical factors increase flood risk?
• Heavy rainfall & storms
• Snowmelt
• Monsoon seasons
• ENSO cycles (La Niña brings heavy rain)
What is a storm hydrograph?
A graph showing changes in river discharge after a storm event.
What 4 factors create a flashy hydrograph and why?
What creates it:
Short lag time, high peak discharge, steep rising and falling limbs
Why?
steep slopes, impermeable rock, deforestation, and urbanisation.
What 2 factors create a subdued hydrograph and why?
Factors:
Long lag time, low peak discharge
Why?
gentle slopes, permeable soil, dense vegetation.
What defines water stress vs water scarcity?
• Water Stress: < 1,700m³ water per person per year.
• Water Scarcity: < 1,000m³ water per person per year.
What 2 physical factors cause water insecurity?
• Climate variability: Uneven rainfall distribution.
• Saltwater intrusion: Rising sea levels contaminate freshwater.
What 3 human factors cause water insecurity?
• Agricultural pollution (fertiliser runoff).
• Over-abstraction of aquifers
• Industrial pollution (mining waste, untreated sewage).
What are the 4 types of drought?
- Meteorological: Less rainfall than normal.
- Agricultural: Soil moisture deficit affecting crops.
- Hydrological: Reduced river & reservoir levels.
- Socio-economic: Demand exceeds supply for industry & society.
How does El Niño cause drought?
Weak trade winds move warm water to South America, causing heavy rain there but dry conditions in Australia & SE Asia.
How does La Niña affect rainfall?
Increased rainfall in Australia & SE Asia but drier conditions in South America.
What is a water budget?
The balance between the water evaporated from the ocean & precipitated on the land
What is water insecurity?
When a population doesn’t have access to enough safe water to meet their demands
Can you give an example of climate variability
(e.g. Sahel (dry region) vs Amazon (wet region)).
Can you give an example of saltwater intrusion?
e.g. Tuvalu (3m above sea level so it’s suffering from sea level rise)
