Eq - 1 Flashcards
Describe a systems approach
A way of studying natural processes by looking at the balance of inputs and outputs and how water is moved between stores by flows.
Stores
Reservoirs where water is held, such as oceans
Fluxes
The rate of flow between the stores
Processes
The physical mechanisms that drive the fluxes of water between the stores
Cryosphere
Areas of the earth where water is frozen into snow or ice
Blue water
Water is stored in rivers, streams, lakes and groundwater in liquid form (the visible part of the hydrological cycle)
Green water
Water stored in the soil and vegetation (the invisible part of the hydrological cycle)
Residence time
The average amount of time a water molecule will spend in a reservoir or store
Fossil water
Ancient, deep groundwater from former pluvial (wetter) periods.
Transpiration
The diffusion of water from vegetation into the atmosphere, involving a change from a liquid to a gas
Groundwater Flow
The slow transfer of percolated water underground through pervious or porous rocks
Throughfall
When rainfall persists or is relatively intense and the water drops from leaves, twigs, needles etc.
Percolation
The deep transfer of water from the surface or soil into the rocks below. permeable rocks - those with joints or those with pores.
Evapotranspiration (EVT)
The combined effect of evaporation and transpiration.
River regime
The annual variation in discharge or flow of a river at a particular point or gauging station is usually measured in cumecs.
What are examples of stores?
- ocean
- ice
- groundwater
- rivers, lakes
- soil moisture
- permafrost
- atmosphere
What is a store
a reservoir where water is held
What are the 3 largest stores and their values
- ocean - 1,334,040 (1000 cubic km)
- Ice - 26,350 (1000 cubic km)
- groundwater - 13,300 (1000 cubic km)
What are examples of fluxes?
- ocean evaporation
- ocean precipitation
- land precipitation
- evaporation transportation
- ocean to land water vapour transport
- surface flow
What is a flux
A measure of the rate of flow between stores
What are the 3 largest fluxes and their values
- ocean evaporation - 413 (1000 cubic km)
- ocean precipitation - 373 (1000 cubic km)
- land precipitation - 113 (1000 cubic km)
What is a closed system
When there is a transfer of energy but no external inputs or outputs. No matter can enter the system
What is an open system
Receives inputs from and transfers outputs of energy and matter to other systems
Is the hydrological cycle an open or closed system
it is a closed system
how much of the earth’s water is stored in oceans (the largest store)
96.5% - 97%
how much of Earth’s water is stored in the cryosphere (the second largest store)
1.9%
What % of water on earth is fresh water?
2.5%
What % of earth’s fresh water is accessible for human use?
1%
What is a drainage basin?
an area of land drained by a river and its tributaries and separated from other drainage basins by a ridge of highland called the watershed.
What is a confluence?
joining point of 2 rivers or streams
What is a tributary?
- near the source
- narrow
- shallow
- small stream
What is the watershed?
- a ridge of steep land
- boundary of the basin
What is surface storage?
puddles, ponds, lakes etc
What is infiltration?
water soaking into the soil
What is surface runoff (overland flow)
water flowing above/along the ground
What are the physical factors that can affect the drainage basin?
- relief -impact amount of precipitation
- climate - type and amount of precipitation
- vegetation - presence or absence impacts amount of interception
- geology - impact on the subsurface processes
- soils - determines the amount of infiltration
When do we see convectional rainfall?
Common in tropical areas and the UK summer time.
What is convectional rainfall?
When 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. If the air continues to rise rain will fall.
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 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.
What effect does the vegetation in Amazonia have?
high interception and evapotranspiration rates which causes high humidity and heavy local conventional rainfall.
What % of the Amazon rainforest has been destroyed?
over 20% at an accelerating rate over the last 50 years.
What effect has deforestation had on the basin?
significantly reducing evapotranspiration and precipitation while also increasing runoff and river discharge E.g. the Tocantins River showed a 25% increase in river discharge between 1960 and 1997, which coincides with increased deforestation.
What effect has deforestation had on the water cycle?
More water runs off into the Amazon drainage system, not only does this exacerbate the problem of floods and mudslides but it also leads to aquifer depletion. overland flow also increases the amount of soil erosion degradation as nutrients are ‘washed away’
What is cloud seeding
Attempt to change the amount or type of precipitation by dispersing substances into the air by plane. Dependable and affordable water-supply practice for many regions but effectiveness is still debated.
When has cloud seeding been used?
CHINA used cloud seeding in BEIJING just before the 2008 OLYMPICS to create rain to clear the air of pollution. it is also used in the ALPINE MEADOWS SKU area of California to improve snow cover. Also used in TEXAS to reduce the impact of drought in 2015
How has urbanisation disrupted the drainage basin - interception and infiltration
Urbanisation creates impermeable surfaces increasing surface runoff, throughflow through artificial drains. Floods across the UK York in 2015
how does dam construction disrupt the drainage basin - evaporation
Dams increase surface water stores and evaporation and reduce downstream river discharge. Lake Nasser behind the river Aswan Dam in Egypt is estimated to evaporate 10 to 16 billion cubic metres every year. represents a loss of 20% to 30% of water volume in the river Nile.
What effects do deforestation have on the basin? - interception
leads to a reduction in evapotranspiration and also an increase in surface run-off. This increases the flooding potential and leads to a decline of surface storage and a decrease in the lag time. in NEPAL there has been increased runoff and therefore risk of flooding in Nepal and Bangladesh and increased soil erosion.
What effects do afforestation have on the basin? - interception
reverses the impacts of deforestation by trapping silt and allowing up the hydrological cycle by lengthening lag times.
What are the effects of groundwater abstraction on the drainage basin? - groundwater levels
Sometimes extracted faster it is replaced, causing reduced groundwater flow and lower water table. sometimes reduced industrial activity or deforestation has increased groundwater storage increasing the risk of groundwater flooding if the water table reaches the land surface.
what is a water budget
the balance between inputs and outputs known as the water budget
water budget formula
- change in storage = precipitation (p) - (runoff (Q) + evapotranspiration(E))
- inputs - ouputs
