Topic 5- Hydrological Cycle Flashcards
What is the global hydrological cycle?
It is a global closed system that of the flows of water between different states around the Earth-atmosphere system.
What are the three systems of operation for the global hydrological cycle?
Stores
Fluxes
Processes
What are stores(stocks)?
Reservoirs where water is held, such as the oceans.
What are fluxes?
The rate of flow between the stores.
What are processes?
The physical mechanisms that drive the fluxes of water between the stores.
What is the global hydrological cycle driven by?
It is driven by solar energy and gravitational potential energy.
What does a closed system mean?
It does not have any external inputs or outputs.
What does a closed system mean for the global hydrological cycle?
This means that there is a fixed amount of water in the Earth- atmosphere system. The amount of water is constant and finite.
What is the systems approach to the global hydrological cycle?
Systems approaches study hydrological phenomena by looking at the balance of inputs and outputs, and how water is moved between stores by flows.
What is the cryosphere?
The areas of the Earth where water is frozen into snow or ice.
Give an example as to why sea levels would drop in reference to the cryosphere.
In the last ice. age more water was held within the cryosphere in a solid form as snow and ice; as less was held in the oceans. sea levels dropped considerably- over 140m lower than they are today.
Give an example as to why sea levels would rise in reference to the cryosphere.
Recent global warming is beginning to lead to major losses of ice in Greenland and, more recently, Antartica, and significant rises in sea levels.
Give an example as to why sea levels would rise in reference to the cryosphere.
Recent global warming is beginning to lead to major losses of ice in Greenland and, more recently, Antartica, and significant rises in sea levels.
How have humans increased the security of their water supplies?
At a small scale, humans have built numerous water storage reservoirs to complement natural lakes in order to increase the security of their water supplies.
What are the four major stores of water?
Coeans(96.5-97%)
Cyrosphere(1.9%)
Terrestrial surface groundwater
Atmosphere
Describe the stores within the global hydrological cycle
- In the oceans, the vast majority of water is stored in liquid form, with only a minute fraction as icebergs.
- In the cryosphere water is largely found in a solid state, with some in liquid form as melt water and lakes.
- On the land the water is stored in rivers, streams, lakes, and groundwater in liquid form. It is often known as blue water. Water can also be stored in vegetation after an interception or beneath the surface in the soil. Water stored in the soil and vegetation is often known as green water.
- Water largely exists as vapour in the atmosphere, with the carrying capacity directly linked to temperature. Clouds can contain minute droplets of liquid water or, at a high altitude, ice crystals, both of which are a precursor to rain.
What is blue water?
Blue water is the visible part of the hydrological cycle.
What is green water?
Green water is the invisible part of the hydrological cycle.
What are the two major fluxes in the hydrological system driven by?
Precipitation, evaporation, cryospheric exchange, and a run-off generation(both surface and groundwater).
What is the most important process of the fluxes?
Evaporation from the oceans and precipitation onto land and the oceans.
What is evaporation?
The change in state of water from a liquid to a gas.
What is residence time?
Residence time is the average time a water molecule will spend in a reservoir or store.
What is fossil water?
Fossil water is ancint, 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 undergoround through pervious or porous rocks.
What is groundwater flow?
The slow transfer of percolated water undergoround through pervious or porous rocks.
What is precipitation?
The movement of water in any form from the atmosphere to the ground.
Why is water stored in the soil easily lost?
Water stored in the soil, for example, remains there very briefly as it is spread very thinly across the Earth. Because of its accessibility it is easily lost to other sites by evaporation, transpiration, groundwater flow or recharge.
Which store has the shortest residence time? For how long and why?
Atmospheric water, 10 days, as soon as it evaporates, condenses and falls to the Earth as precipitation. Atmospheric water is forced to fall as precipitaton due to gravitational potential energy and weight of the clouds.
Whta is the link between residence times and levels of water pollution?
There is a strong link between these two as the stores that are longer in situ tend to be more polluted.
Where is the vast majority of Earth’s fresh water supply located?
Around 69% is locked up in snowflakes, ice sheets, ice caps and glaciers found in high altitude locations.
Why is the vast majority of our fresh water supply being locked up in glaciers and ice sheets an issue?
It is largely inaccesible for human use, although some streams in mountain areas are ‘fed’ from ice and snow as melt water. 30% of freshwater comes from groundwater which is very inaccesible and therefore only around 1% of freshwater is actually accesible, this means that agricultural and urban development maybe slower without a lot of water fuelling the development of sectors.
What are humans main source of surface water?
Rivers are humans main source of water, however, this only constitutes 0.007% of total water. This is why there are so many disputes about the usage of all this water.
How is technology being used to extend the availabilty of fresh water supplies?
The desalination of ocean water which which is used as fresh water due to the highly advanced filtration and advanced chemicals used to desalinate the water.
What is the drainage basin water cycle?
On a small scale(variable from regional to local, depending on the size of the drainage basin) the drainage basin is a subsystem within the global hydrological cycle. It is an open system as it has external inputs and outputs that cause the amount of water in the basin to vary over time.
How often do conditions vary in the drainage basin cycle?
The variations in the drainage basin cycle can occur at different temporal scales, from short-term horuly through to daily, seasonal and annual.
Define a drainage basin
The area of land drained by a river and its tributaries, and is frequently reffered to as a river catchment.
What is a watershed?
The highland which divides and separates water flowing to different rivers.
How big are drainage basins?
Drainage basins can be of any size, from a small stream possibly without tributaries up to a major international river flowing across borders of several countries.
What are the flows in the global hydrological cycle?
Precipitation Cryospheric processes Vapour transport Surface run-off Evaporation Atmosphere Transpiration Evaporation Precipitation Groundwater Soil Percolation Ocean
What are the stores in the drainage basin cycle?
Soil Lake Groundwater Surface River flow Interception
What are the inputs into the drainage basin?
Precipitation
Solar and gravitational energy
What are the outputs in the drainage basin cycle?
Evaporation from water surfaces
River discharge
Evaporation and transpiration from vegetation.
What are the flows in the drainage basin?
Soil Rock Infiltration Overland flow Throughflow Base flow Channel fall Evaporation
What are the conditions necessary for precipitation to form?
Air cooled to saturation poijnt with a relative humidity of 100%.
Condensation nuclei, such as dust particles, to facilitate the growth of droplets in clouds.
A temperature below dew point
What are the main influencing factors for the drainage basin hydrological system? Describe each
- The amount precipitation, which can have a direct impact on drainage discharge: as a general rule, the higher the amount the less variability in its pattern.
- The type of precipitation(rain, snow or hail): the formation of snow, for example, can act as a temporary store and large fluxes(flows) of water can be released into the system after a period of rapid melting resulting from a thaw.
- Seasonality. In some climates, such as monsoon, Mediterranean or continental climates, strong seasonal patterns of rainfall or snowfall will have a major impact on the physical processes operating in the drainage basin system.
- Intensity of precipitation is also a key factoras it has a major impact on flows on or below the surface. It is difficult for rainfall to infiltrate if it is very intense, as the soil capacity is exceeded.
- Variability can have a major impact: Secular variability happnes long term, for example as a result of climate change trends. Periodic variability happens in an annual, seasonal, montly or diurnal context. Stochastic variability results from random factors, for example in the localisation of a thunderstorm within a basin.
- The distribution of precipitation within a basin. The impact is particularly noticeable in very large basins such as the Rhone or the Nile, where tributaries start in different climatic zones. At a local scale and shorter time scale the location of a thunderstrom wihtin a small rover basin can have a major impact temporarily as inputs will vary, with contrasting strom hydrographs for different stream tributaries.
What is interception?
Interception is the process by which water is stored in the vegetation. It has three main components: interception loss, throughfall and stem flow.
What is condensation?
Condensation is the change from a gas to a liwuid, such as when water vapour changes into water droplets.
What is dew point?
Dew point is the temperature at which dew forms, it is a measure of atmospheric moisture.
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 holdwater vapour decreases. Condensation occurs an clouds develop. If the air continues to rise, rain will fall. (the clouds formed are cumulous clouds)§
What is cyclonic rainfall?
Cyclonic rainfall happens when warm air, which is lighter and less dense, is forced to rise over cold, denser air. As it rises, the air cools, and its ability to hold water vapour decreases. Condensation occurs and clouds and rain form.
What is orographic rainfall?
When air is forced to rise over a barrier, such as a mountain, it cools and condensation takes place forming rain. The leeward (downward) slope receives relatively little rain, which is known as the rain shadow effect.
