The water cycle Flashcards
What is the drainage basin?
An area of land which is drained by a river and its tributaries.
What is the drainage basin system?
The movement of water within the drainage basin.
Is the drainage basin an open or closed system?
Open, inputs (precipitation), outputs (runoff, evapotranspiration)
Describe groundwater flow and its role in the drainage basin system
Feeds rivers through their banks and beds.
Slow transfer, therefore, keeps the river running during dry periods.
Describe the role of precipitation and how it is transferred in the drainage basin
Input to the system.
Infiltrates through vegetation.
When it reaches the ground it’s stored as overland flow (puddles), or is infiltrated into the soil.
What effects the rate of infiltration?
Saturated soils have a lower infiltration capacity.
Trees encourage infiltration at the roots.
What is overland flow and where is it common?
When water is unable to infiltrate through the soil it runs over the surface.
Common in urban areas due to impermeable surfaces,
Describe how different soils affect throughflow.
Sandy soils - absorb and transfer
Clay - slow drainage rate
If bedrock is impermeable there is no more downward movement.
What causes variations in runoff?
Soil saturation, rock type, vegetation cover
Intensity of precipitation.
Time of year; effects rates of evapotranspiration and vegetation growth
Give some examples of the stores in the water cycle
vegetation, interception, groundwater, surface water, soil
Give some examples of flows in the water cycle
overland flow, infiltration, stem flow, channel flow
Where is most of the earths water stored?
Oceans, in the hydrosphere
Explain evaporation and condensation
Evaporation - liquid to gas
Condensation - gas to liquid
What is the equation for the water balance?
Precipitation = total runoff + evaporation +/- storage
Name some characteristics of the water cycle seen in the rainforest
- High levels of precipitation due to high humidity
- 75% of rainfall intercepted
- 25% evaporated
- Of the remaining 75% ;
50% used by plants/evapotranspiration
50% infiltrated
Name some impacts of human activity on the water cycle in the rainforest
- Atmosphere less humid, less evapotranspiration
- Soil is compacted by direct rainfall, increases runoff
- Soil is exposed to sun, vulnerable to erosion
- Less interception, less evapotranspiration off leaves
Explain how natural variations affect changes in the water cycle
Extreme weather conditions (severe storms or periods of dorughts)
Name some human activities which affect change in the water cycle
- Land use changes
- Farming practices
- Water abstraction
Explain how change in land use affects the water cycle
- Urbanisation: replaces vegetation with impermeable surfaces, reducing infiltration and increasing runoff. Soil storage and groundwater stores reduced
- Deforestation: removal of trees leading to surface runoff and soil erosion (less interception and infiltration)
Explain how farming practices affect the water cycle
Soils covered with vegetation have higher infiltration rates and can hold more water
Desertification reduces soil storage capacity
Explain how water abstraction affects the water cycle
Abstraction of water from rivers or aquifers
Aquifers can become depleted and contaminated by inflowing saltwater
Irrigation and land drainage
Name some processes which change the magnitude of the water cycle stores
- Precipitation
- Evaporation
- Condensation
- Infiltration
- Interception
Name some processes of change at a local level
- Deforestation
- Urbanisation
- Farming
- Storms
- Seasonal changes
What is water surplus and what does it cause
Precipitation exceeds evapotranspiration
River levels rise
More runoff and discharge
