The water/ hydrological cycle EQ1 Flashcards
what is the most common water store
oceans (97.5%)
what is the most common freshwater store
ice caps and glaciers (69%)
what is the most common accessible surface freshwater
lakes (52%)
what two water stores are non-renewable
fossil water(untapped ancient stores off fresh water)and the cryosphere
whats the cryosphere
frozen snow or ice
whats fossil water
ancient deep underground water from the geological past
why does a drainage basin vary in the amount of water it holds
because its an open system with inputs and outputs, these inputs may vary with time
what is a drainage basin
an area of land that is drained by a river and its tributaries, sometimes referred to as a river catchment. The boundary of a drainage basin is defined by the watershed.
what 5 characteristics have a significant impact on the drainage cycle
-form- rain snow or hail- entry of snow into a drainage system would be delayed
-amount-
-intensity- higher intensity= more likely to flood
-seasonality- different flow levels at different times of the year
-distribution- some tributaries may start in diff climate zones
what are the 7 flows important in transferring precipitation into a drainage network
-interception
-infiltration
-percolation
-throughflow
-groundwater flow
-surface runoff
-river/channel flow
what are the 3 types of precipitation
orographic
frontal
convectional
define the flow: interception
when vegetation takes up water
define the flow: infiltration
where water is absorbed/ taken in via the soil. water enters the topsoil and may move into the soil and rock below.
define the flow: percolation
a deep transfer of water into rocks (downwards seepage)
define the flow: throughflow
the lateral transfer of water downslope through the soil
define the flow: groundwater flow
Water contained within the soil and underlying rocks, and derived mainly from the percolation of rainwater and meltwater. (Very slow transfer of percolated water through porous rock)
define the flow: surface runoff
movement of water across the surface of the ground (also known as overland flow)
define the flow: river/ channel flow
the flow once water enters a stream/ river; the flow is confined within a river
what are the 3 main outputs of a drainage basin
-evaporation- ( moisture lost directly into the atmosphere)
-transpiration- ( the loss of water vapour from plants)
-discharge- movement of water into the sea, lake or another larger drainage basin ( also know as channel flow))
What are the 5 physical factors affecting drainage basins
-climate
-soils
-geology
-relief
-vegetation
how does the physical factor of climate affect drainage basins
- has a role in influencing the type and amount of precipitation overall and the amount of evaporation- climate also influences vegetation type
how does the physical factor of soils affect drainage basins
soils determine the amount of infiltration and throughflow and indirectly the type of vegetation
how does the physical factor of geology affect drainage basins
geology can impact on subsurface processes such as percolation and groundwater flow (and therefore impact aquifers) Indirectly, geology affects soil formation.
how does the physical factor of relief affect drainage basins
relief can impact the amount of precipitation. slopes affect the amount of runoff
how does the physical factor of vegetation affect drainage basins
the presence or absence of vegetation ahs a major impact on amount of interception, infiltration and occurrence of overland flow, as well on transpiration rates.
What are the 4 human factors affecting drainage basins
-river management
-deforestation
-changing land use ( agriculture)
- changing land use ( urbanisation)
How does the human factor of river management affect drainage basins
-construction of storage reservoirs holds back river flows
-abstraction of water for domestic and industrial use reduces river flows
-abstraction of groundwater for irrigation lowers water tables
How does the human factor of deforestation affect drainage basins
-clearance of trees reduces evapotranspiration, but increases surface runoff*
How does the human factor of changing land use (agriculture) affect drainage basins
-(arable to pastoral)- compaction of soil by livestock increases overland flow
-(pastoral to arable)- ploughing increases infiltration by loosening and aerating the soil
What does an open system receive?
Inputs from and transfers outputs of energy and matter to other systems.
Why is a hydrological cycle a closed system?
Because all the water is continually circulated through the stores and there is a constant amount of water in the system. The system does not change because there are no gains from or losses to other systems.
What is the global circulation of water driven by?
Solar energy and gravitational potential energy.
How does solar energy drive the cycle?
Global circulation of water is heated by the sun, water on the Earth’s surface evaporates into the atmosphere, while water is also drawn from the soil by plants and evaporated from leaves and stems by the process of evapotranspiration.
What happens when humid air rises?
Condensation occurs at the cooler temperatures, forming clouds, and this eventually leads to precipitation and water is returned back to the land and oceans on the Earth’s surface.
On land, what is gravitational potential energy converted to?
Kinetic energy as the water moves through the system by plant interception, or over land as surface runoff. Water also flows through the soil by processes of infiltration and throughflow.
What happens when water flows through soil by the processes of infiltration or throughflow?
Here it may be stored as soil moisture, or if the bedrock is permeable or porous, will percolate into the rock where it’s stored as groundwater. Some of this water will return to the oceans via streams and rivers
As the global hydrological system is a closed system of interlinked processes, what does this mean for the amount of global water?
It is finite and constant.
What does gravitational potential energy do in the hydrological cycle?
Causes rivers to flow downhill and precipitation to fall to the ground. Keeps water moving through the system in a sequence of inputs, outputs, stores and flows
What happens when more evaporation occurs as the climate warms?
- Increases moisture levels in the air
- Therefore greater condensation and precipitation.
What are the four main water stores?
- oceans
- cryosphere
- surface runoff (land based stores such as lakes and rivers)
- the atmosphere
define annual fluxes
the movement of water between stores over the course of the year
What are fluxes?
The rates of flow between stores.
Where do the greatest fluxes occur?
Over the oceans.
What is the second largest freshwater store?
groundwater (30% of global freshwater)
Less than 1% of freshwater is stored where?
In the biosphere ( vegetation and soil moisture)
In the system of inputs, outputs, stores and flows, what are the 5 𝘀𝘁𝗼𝗿𝗲𝘀 in this system?
- interception storage
- surface storage
- soil moisture storage
- groundwater storage
- channel storage
About ____ of the Earth’s surface is water-covered.
71%
What’s the problem with glaciers being the largest freshwater store?
They’re predicted to melt, so could be a problem.
Is there more water stored in the soil or in the atmosphere/rivers?
More water stored in the soil!
What are flows also referred to as?
Transfers.
Define 𝘃𝗲𝗴𝗲𝘁𝗮𝘁𝗶𝗼𝗻 𝘀𝘁𝗼𝗿𝗮𝗴𝗲
Any moisture taken up by vegetation and held within plants.
Define 𝘀𝘂𝗿𝗳𝗮𝗰𝗲 𝘀𝘁𝗼𝗿𝗮𝗴𝗲
Any surface water in lakes, ponds, puddles.
Define 𝗴𝗿𝗼𝘂𝗻𝗱𝘄𝗮𝘁𝗲𝗿 𝘀𝘁𝗼𝗿𝗮𝗴𝗲
Water held within permeable rocks (also known as an aquifer)
Define 𝗰𝗵𝗮𝗻𝗻𝗲𝗹 𝘀𝘁𝗼𝗿𝗮𝗴𝗲
Water held in rivers and streams.
Define 𝗯𝗮𝘀𝗲 𝗳𝗹𝗼𝘄 (groundwater flow)
Slow-moving water that seeps into a river channel.
Define 𝗰𝗵𝗮𝗻𝗻𝗲𝗹 𝗳𝗹𝗼𝘄
The volume of water contained within a river channel (also called discharge and runoff)
Define 𝗿𝗶𝘃𝗲𝗿 𝗱𝗶𝘀𝗰𝗵𝗮𝗿𝗴𝗲
The volume of water passing a certain point in the channel over a certain amount of time.
define blue water
the amount of rainfall that enters lakes, rivers and groundwater
define greenwater
the amount of water that is either intercepted by vegetation or enters the soil and is picked up by plants and evapotranspired back into the atmosphere
What is the largest flux?
the ocean
what is residence time
the average amount of time that water remains in each store
What is fossil water?
untapped ancient stores of freshwater, these are often non-renewable
What are two stores with the longest residence time?
-oceans and seas (4000 years)
-groundwater (up to 10,000 years)
whats a non renewable water store
one that is not naturally recharging and is finite
What is the store with the shortest residence time?
Biospheric water (1 week)
whats the global water budget
the balance of water between the stores in the hydrological cycle
How could water be considered a renewable resource?
its at constant circulation and replenished naturally
What percentage of freshwater is locked up in glaciers and ice sheets?
A
70%. Only 1% of all freshwater is “easily accessible surface freshwater”.
Do oceans lose more water through evaporation or gain more water from precipitation?
Lose more water through evaporation.
Do landmasses lose more water through evaporation or gain more water from precipitation?
Gain more from precipitation.
What makes up the difference between the processes from oceans and landmasses?
Surface runoff - known as the balance.
What happens if this balance (oceans losing more water through evaporation rather than gaining more from precipitation) is disturbed?
the ocean would receive more water than the continents which would be dry. The global water budget ensures this doesn’t happen
whats a drainage basin
an area of land drained by a river and its tributaries and separated from neighbouring drainage basins by a ridge of high land called a watershed or divide.
it includes water found in the water table and surface runoff.
Is a drainage basin an open or closed system?
An open system. It’s a subsystem within the global hydrological cycle linked to other systems by inputs and outputs and involves a number of linked processes and stores.
define watershed
the boundary of a drainage basin, a high ridge of land marking the edge if a drainage basin .
what is the water table
the boundary between the unsaturated zone and the saturated zone underground.
whats a confluence
occurs when two or more flowing bodies of water join together to form a single channel.
The drainage basin is an open…
subsystem in the hydrological cycle
simply, how has the worlds largest tropical rainforest’s drainage basin been disrupted
by deforestation
how has deforestation in the Amazonia affected the drainage basin cycle
-has lowered humidity’s
-less precipitation
-more surface runoff
-more evaporation, less transpiration
-more soil erosion and slit being fed into the rivers.
what do water budgets at a national and regional scale provide as
provide as a useful indication of the amount of water that is available for human use (for agriculture, domestic consumption etc…)
what do water budgets at a local scale provide as
informs us about the available soil water- valuable to farmers who can identify when and how much irrigation may be required
what is a river regime
the annual variation in the discharge or flow of the river at a particular point, and is usually measured in cumecs.
the character of a river rescheme is influenced by many factors: (6)
-the size of the river and where discharge measurements are taken along its course
-the amount, seasonality and intensity of the precipitation
-the temperatures, with possible meltwater and high rates of evaporation in the summer
-the geology and soils, particularly their permeability and porosity; groundwater noted in permeable rock is gradually released into the river as base flow
-the type of vegetation cover: wetlands can hold water and release it slowly into the river
-human activities aimed at regulating the rivers discharge
a water budget graph for a cool temperate location:
- what is happening at A where precipitation> potential evapotranspiration
soil water store is full and there is soil moisture surplus for plant use. Runoff and groundwater recharge.
a water budget graph for a cool temperate location:
- what is happening at B where potential evapotranspiration > precipitation
the water store is being used up by plants or lost by evaporation (soil moisture utilization)
a water budget graph for a cool temperate location:
- what is happening at C where he soil moisture store becomes used up
Any precipitation is likely to be absorbed by the soil rather than proceed with runoff. River levels fall or dry up completely
a water budget graph for a cool temperate location:
- what is happening at D where there is a deficiency in the soil water as the store has been used up and evapotranspiration> precipitation
-plants must adapt to survive, crops must be irrigated
a water budget graph for a cool temperate location:
- what is happening at E where precipitation> potential evapotranspiration
soil water store starts to fill again (soil moisture recharge)
a water budget graph for a cool temperate location:
- what is happening at F where the soil water store is full
field capacity has been reached. Additional rainfall will percolate down to the water table and groundwater stores will be recharged
what is the most important factor affecting river reschemes
climate
what amount of time are storm hydrographs plotted over
plotted over a short period of time- a few days
what are the main features of a storm hydrograph
-the rising limb
-peak discharge
-lag time
-falling/ recessional limb
-base flow
storm hydrographs: define rising limb
where the discharge starts to rise after the rainfall starts
storm hydrographs: define peak discharge
reached after the peak rainfall, its the greatest volume of water, flooding may occur
storm hydrographs: define lag time
the interval between the peak rainfall and the peak discharge
storm hydrographs: define falling/recessional limb
once the input of rainwater starts to decrease so does the discharge
storm hydrographs: define base flow
where the rivers discharge eventually returns to normal
whats a flashy hydrograph
hydrographs with very steep limbs, especially rising limbs, a high peak discharge and a small lag time
whats a flat hydrograph
hydrographs with gently inclined limbs, a low peak discharge and a long lag time.
what are the ways in which urbanisation affects storm hydrographs.
- construction works leads to the removal of veg cover. Exposes soil and increases overland flow
-Bare soil replaced by concrete and tarmac= impermeable. Increases surface runoff
-High density of buildings=rain falls on roofs and moves into gutters and pipes swiftly
-Drains and sewers reduce the distance and time rainwater travels b4 reaching a stream or river channel
-urban rivers are often channelized with embankments to guard against flooding, when floods occur they can be more devastating
-bridges can restrain the discharge of floodwaters and act as local damns, thus prompting upstream floods.
talk about the factor of weather and climate and how it affects a flashy river
-intense storm that exceeds the infiltration capacity of the soil.
-rapid snowmelt as temps suddenly rise above 0
-low evaporation rates due to low temperatures
talk about the factor of weather and climate and how it affects a flat river
-steady rainfall that is less than the infiltration capacity of the soil
-slow snowmelt as temperatures gradually rise above 0
-high evaporation rates due to high temperatures
talk abt rock type and how it affects a flashy river
-impermeable rocks, such as granite which restrict percolation and encourage rapid surface runoff
talk abt rock type and how it affects a flat river
-permeable rocks such as limestone , which allow percolation and so limit surface runoff
talk abt relief and how it affects a flashy river
-high, steep slopes that promote surface runoff
talk abt relief and how it affects a flat river
-low, gentle slopes that allow infiltration and surface runoff
talk abt basin size and how it affects a flashy river
-small basins tend to have more flashy hydrographs.
talk abt basin size and how it affects a flat river
-larger basins tend to have a more delayed hydrographs; it takes time for water to reach gauging stations
talk abt shape and how it affects a flashy river
- circular basins have a shorter lag time
talk abt shape and how it affects a flat river
-elongated basins tend to have delayed or attenuated hydrographs
talk abt drainage density and how it affects a flashy river
-high drainage density= more streams and rivers per unit area, so water will move more quickly to the measuring point
talk abt drainage density and how it affects a flat river
-low drainage density= few rivers and streams per unit area, so more water is likely to enter the ground and move slowly through the basin
talk abt vegetation and how it affects a flashy river
bare/ low density, deciduous in winter, means low levels of interception and more rapid movement through the system
talk abt vegetation and how it affects a flat river
dense, deciduous in summer, means high levels of interception and slower passage through systems; more water lost to evaporation through vegetation surfaces
talk abt pre existing (antecedent) conditions and how it affects a flashy river
-basin already wet from previous rain, water table high, soil saturated so low infiltration/ percolation.
talk abt pre existing (antecedent) conditions and how it affects a flat river
-basin dry, low water table, unsaturated soils, so high infiltration/percolation
talk abt human activity and how it affects a flashy river
-urbanisation producing impermeable concrete and tarmac surfaces. deforestation reduces interception
-arable land, downslope ploughing
talk abt human activity and how it affects a flat river
- low population density, few artificial impermeable surfaces.
-reforestation interception
-pastoral, moorland and forested land
what is the rain-shadow effect
the eastern side of the UK receives less rainfall than the west, because the western hills force moist air to rise as it approaches from the Atlantic- leading to orographic rainfall in the north and west.
what is convectional rainfall
this is typical of the eastern and south-eastern UK in summer. During periods of high temperatures, the rainfall created is often intense and associated with electrical storms and thunder.
what is frontal rainfall
this is where a cold airmass reaches a warm air mass. This brings most rainfall to the UK over a year. fronts are formed as part of a low pressure area (called a depression). When warm air meets polar air, the warmer air is forced to rise over the denser colder air- forming rain along both warm and cold fronts.
what is orographic (or relief) rainfall
the western side of the UK receives the highest rainfall totals. Warmer, moist Atlantic air ( from the couth west) is forced to rise as it reaches the western uplands. as it rises, it cools over the high ground - producing heavy rain over western and northern parts of the UK
how does an equatorial climate affect a river rescheme
heavy rain (high water soil availability), regular convectional rainfall, gives the rescheme a double peak. low pressure
how does a tropical climate affect a river rescheme
distinct wet and dry seasons, during dry seasons, the river may dry up completely
how does a humid climate affect a river rescheme
areas influenced by the sea have rainfall throughout the years
how does a Mediterranean climate affect a river rescheme
winter rainfall and summer droughts
how does a continual snowmelt climate affect a river rescheme
heavy winter snowfall causes a rapid rise in river levels
how does a mountain climate affect a river rescheme
high river flow in spring caused by melting of snow and ice
how does a desert climate affect a river rescheme
river systems dry- low water availability
what are flows
the transfer of water from one store to another
what are the four flows (transfers from one store to another)
-precipitation
-evaporation
-transpiration
-vapour transport
what region would have a water deficit (negative water balance, more outputs than inputs)
deserts
what region would have a water surplus (positive water balance, more inputs)
tropical rainforest
what region would ahve a slightly positive water balance
tundra regions- slightly positive due to little evaporation as there is little heat.
state things abt amazon river
-its in a humid tropical climate
-its peak discharge is in april-may and lowest discharge is in sept which is linked to wet and dry seasons . affected by wet and dry seasons
state things abt the river nile
-has been significantly changed by the construction of the Aswan Dam in 1970. The flow below the dam was reduced by 65%.
what is the hydrological cycle
the constant transfer of water between land land, atmosphere and water (closed system)
what is fossil water
untapped ancient stores of fresh water
-can be accessed through aquifers.
