The water cycle Flashcards
What happens in the water cycle at a local scale?
In the local drainage basin system, water may be lost as an output through evapotranspiration and run off, but more water may be gained as an input through precipitation, as the inputs and outputs are not balanced, it is an open system
What are inputs in the water cycle (local)
Precipitation
What are outputs in the water cycle (local) ?
-evaportranspiration
-Streamflow
What are stores in the water cycle? (local)?
-Groundwater
-Soil water
-Rivers
-Interception
What are flows in a water cycle (local)?
-Infiltration
- Percolation
-Throughflow
-Surface run flow
-Groundwater flow
-Streamflow
-Stemflow
What is the water balance?
Used to express the process of water storage and transfer in a drainage basin system
What is the formula for water balance?
Precipitation = total runoff + evapotranspiraton +/- storage
What is evapotranspiration?
The combined return of water to the atmosphere from evaporation and transportation (plants)
What is streamflow?
Water that flows through streams and into oceans or as tributaries to other rivers
What is groundwater?
Water stored in the pore spaces of rocks
What is interception?
Water stored temporarily by trees etc, before it reaches the ground surface
What is infiltration?
Water moving from above the ground into the soil
What is percolation?
Water moves from the ground or soil into porous rock or rock fractures
What is throughflow?
Flow of water through the soil
What is stem flow?
Flow of water that has been intercepted by plants or trees, down a stem, leaf, branch or other part of a plant
What is the water cycle at a local scale impacted by?
-Deforestation
-Storm events
-Seasonal changes
-Agriculture
-Urbanisation
How does deforestation impact the water cycle?
Less interception, soil less able to store water
How do storm events impact the water cycle?
Increases runoff and water storage
How do seasonal changes impact the water cycle?
More interception in spring; snow reduces flows; hot weather reduces precipitation
How does agriculture impact the water cycle at a local scale?
Ground trampled on so less infiltration
How does urbanisation impact the water cycle?
Impermeable surfaces increase runoff
What does the soil water budget show?
Shows the annual balance between inputs and outputs in the water cycle
How can there be a deficit of soil water?
When evaporranspiration is greater than precipitation
What is field capacity?
Maximum storage of water in the soil
What is the water budget based on ?
Type, depth and permeability of the soil and bedrock
Where can water be stored?
-Hydrosphere
-Lithosphere
-Cryosphere
-Atmosphere
What is the hydrosphere?
Any liquid water
What is the lithosphere?
Water stored in the crust and upper mantle
What is the cryosphere?
Any water that is frozen
What is the atmosphere?
Water vapour
What are aquifers?
Underground water stores and on a global scale are unevenly distributed
What are shallow groundwater aquifers?
Store water for up to 200 years, but deeper fossil aquifers, formed during wetter climatic periods, may last for 10,000 years
How long can glaciers store water for?
20-100years
How long do seasonal snow cover and rivers store water for?
2-6 months
How long does soil water hold water for?
1-2 months
What are seasonal changes ?
-Less precipitation and more evaporation in the summer
-Reduced flows in the winter as water is stored as ice
-Reduced interception in the winter, deciduous trees loose leaves
-Increased evapotranspiration in summer as trees have leaves and warmer
Impact of farming practices on water cycle globally?
-Ploughing breaks up surface increasing infiltration
- Crops can increase interception and evapotranspiration
-Animal farming compacts soil, reducing infiltration and increasing run off
Impact of land use change on the global water cycle?
-Deforestation reduces interception, evapotranspiration.
-Construction reduced infiltration and evapotranspiration but increases run off
What is water abstraction?
Water removed from stores for human use
How does water abstraction impact the water cycle?
-Reduced the volume of water in surface stores such as lakes
-Water abstraction increases in dry seasons
-Decline in global long term water stores
What is a flood hydrographs?
Used to represent rainfall for the drainage basin of a river and the discharge of the same river on a graph
What is a flashy hydrograph?
-Short lag time
-Steep rising and falling limb
-Higher flood risk
-High peak discharge
What is a subdued hydrograph?
-Long lag time
-Gradually rising and falling limb
-Lower flood risk
-Low peak discharge
What is discharge?
The volume of water passing through a cross sectional point of the river
What is the rising limb?
The line on the graph that represents discharge increasing
What is the falling limb?
The line on the graph that represents discharge decreasing
What is the lag time?
The time between peak rainfall and peak discharge
What is the base flow?
The level of groundwater flow
What is the storm flow?
Compromised of overland flow and through flow
What factors would increase surface runoff and create a flashy hydrographs?
-Elongated basin = precipitation reaches river in shorter distance
-Large relief = water flow speed is aided by gravity (shown by contours)
-Impermable surfaces = increase in surface runoff due to decreased infiltration
-Higher rainfall intensity
What is the ITCZ ? (inter-tropical convergence zone)
The global atmospheric circulation model determines cloud formation and rainfall. The ITCZ is along the equator and an area of low pressure which has very heavy rainfalls
-The zone moves during seasons (north and south)
