The Water Cycle Flashcards
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
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)).
