Topic 5 EQ1 Flashcards
What is a closed system?
When there is a transfer of energy but not matter between the system and it’s surroundings. There are no external inputs/output, any inputs come from within the system.
What are flows(fluxes)?
Measurement of the rate of flow between stores
What are processes?
The physical mechanisms such as evaporation that drive the flows of water between the stores.
What are stores?
Reservoirs where water is held eg oceans
What is blue water?
Water that is stored in rivers, streams, lakes and groundwater.
What is green water?
Water stored in vegetation
What is the global hydrological cycle an example of?
A closed system driven by solar energy and gravitational potential energy.
What is the estimated fixed amount of water in the Earth?
1385 million km cubed
What is the cryosphere?
Areas of the Earth where water is frozen into snow or ice.
What are the main global water stores?
Oceans
Icecaps
Groundwater
Rivers and lakes
Soil moisture
Atmospheric moisture
What percentage of total water and fresh water does the ocean have?
Of total : 96.9%
Of fresh: 0%
Residence time of ocean
3600 years
Residence time of ice caps
15,000 years depending on size
Residence times of ground water
Up to 10,000 years for deep ground water but 100- 200 years for shallow groundwater.
Residence times for rivers and lakes
2 weeks to 10 years; 50 years for very large scale
Residence time for soil moisture
2-50 weeks
Residence time for atmospheric moisture
10 days
What is precipitation?
The movement of water in any form from the atmosphere to the ground.
What is evaporation?
The change in state of water from liquid to a gas.
What are residence times?
The average time a water molecule will spend in a reservoir or store
What is fossil water?
Ancient, deep groundwater from former pluvial (wetter) periods.
What is transpiration?
The diffusion of water from vegetation into the atmosphere, involving a change from a gas to a liquid.
What is groundwater flow?
The slow transfer of percolated water underground through permeable or porous rocks.
What is the link between residence times and levels of water pollution?
Stores with slower turnover tend to be more easily polluted as the water is in situ for a longer length of time.
What percentage of water is fresh?
2.5%
What percentage of fresh water is accessible?
1.2%
Is water renewable?
The constant circulation of water means generally water is a renewable resource. However an imbalance across countries is adding pressure to the cycle. Ice stores from glacial melting is being lost without being replenished.
What is interception?
The storage of water when it lands on vegetation or buildings before it reaches the soil. It is a temporary store before evaporation or stemflow.
What is surface storage ?
Storage of water on the surface such as ponds, puddles, lakes
What is soil moisture?
Storage of water in soil. Water is held in small gaps between soil particles.
What is ground water storage?
The storage of water in the ground rocks of permeable rock. The water is held in cracks (limestone) bedding planes (sedimentary rock) or pores (chalk). Rocks with lots of water storage are called aquifers.
What is channel flow?
Storage of water in the river channel. As water is being transported to the sea it is a store of water.
What is vegetation storage?
The storage of water in the vegetation. Plants and trees take up water through their roots and water is stored here.
What is surface run off?
The horizontal flow of water over the surface of the land.
What is throughfall?
The downward flow of water moving downwards from interception storage to the surface.
What is throughflow?
The horizontal flow of water moving through soil towards the river.
What is infiltration?
The downwards movement of water from the surface into the soil.
What is percolation?
The downward movement of water from the soil to the permeable ground rock.
What is base flow?
The horizontal movement of moving through the rock slowly towards the river.
What is channel flow?
The movement of water in the river channel moving towards the sea.
What is evapotranspiration?
Combined output of evaporation and transpiration
What is river discharge?
The output of water from a river channel out to sea
Factor affecting drainage in a drainage basin
- snow capped peaks hold water back until thaw
- steep slopes promote faster faster movement
- permeable soil and rock allow more infiltration
- large drainage basin collect more water
- vegetation means more interception
What is the global water budget?
Oceans lose more water to evaporation than they gain to precipitation but the opposite is true for land. Surface run off makes up the difference which is known as the balance. If the balance was disturbed, oceans would receive more water and continents would dry up. The water budget ensures this doesn’t happen.
The importance of the tropics
Intense solar radiation which causes high evaporation. Trade winds transfer water Vapor towards the ITCZ in which strong convectional currents lift the air so that it cools and condenses into clouds causing heavy rainfall
Importance of the polar regions
- 2/3s of the Earths fresh water is locked up in the cryosphere
- polar regions contribute to the circulation of water and transfer of heat around the world. This helps the ocean thermohaline circulation to occur
How does precipitation vary in the drainage basin
- amount of precipitation:impact drainage discharge
- type of precipitation (rain, snow, hail) eg formation of snow can act as a temporary
- seasonality
- intensity
What is convectional rainfall?
When the land becomes hot, the air above it becomes warmer, expands and rises. As it rises, the air cools and its ability to hold water vapour decreases. Condensation occurs and clouds develop.
What is cyclonic rainfall
When warm air which is lighter and less dense, is forced to rise over cold, denser air. As it rises the air cools and condenses.
What is orographic rainfall
When air is forced to rise over a barrier such as a mountain. The downwind slope receives little rain which is known as the rain shadow
What is a rain shadow
A dry area on the leeward (downwind) side of the mountain. It receives little rainfall as the mountains shelter it from rain. This is because the moist air loses lots of its water vapour as a result of adiabatic cooling. The air without much water left in it , is then drawn over the mountains where it descends.
What is overland flow?
-concept developed by Horton
- saw this as the main way that rain water was transferred to the river channel
- precipitation intensity must exceed the infiltration rate eg intense storm or prolonged rainfall
-unvegetated land have limited infiltration capacity so there is more overland flow
Consequence of overland flow
Primary agent of soil erosion:
-rain splash, sheet, rill and gully erosion
What is potential evapotranspiration?
The water loss that would occur if there was an unlimited supply of water in the soil
How can climate influence the drainage basin cycle?
- Influences the amount and type of precipitation and the amount of precipitation
- also has an impact on vegetation type
How can soil influence the drainage basin cycle?
-amount of infiltration
- amount of through flow
-type of vegetation
How can geology influence the drainage basin cycle?
Impact subsurface processes such as percolation and ground water flow and aquifers
How can relief affect the drainage basin cycle?
Altitude can impact precipitation. slopes can affect the amount of run-off
How can vegetation affect drainage basin cycles?
Affect the amount of interception and infiltration
What is cloudseeding?
Introduction of silver iodide pellets or ammonium nitrate to act as condensation nuclei
Human impact on evaporation and evapotranspiration
Deforestation - decreased evapo transpiration
Artificial reservoir - increased evaporation.For examples,Aswan dam and lake Nasser in Egypt
Channelisation of rivers into conduits cuts down surface storage and evaporation
Human impact on interception
Deforestation leads to reduced evapotranspiration and an increase in surface run off
