water Flashcards
stores/stocks
reservoirs where water is stored e.g the oceans
fluxes
measure the rate of flow between stores
processes
physical mechanisms which drive the fluxes of water between the stores.
cryosphere
areas of earth where water is frozen into snow/ice. During the last ice age sea levels were 140m lower than they are today.
systems approach
systems approaches study hydrological phenomena by looking at the balance of inputs and outputs, and how water is moved between stores and flows.
open system
receives inputs from and transfers outputs of energy to other systems. For example a drainage basin.
closed systems
Fixed amount of water in the earth and atmosphere system (1385 milion km³). There are no external inputs or outputs- the amount of water is constant. For example the hydrological cycle.
blue water
water is stored in rivers, streams, lakes and groundwater in liquid form
green water
Water stored in the soil and vegetation.
residence time of oceans
3,600 years
residence time of ice caps and glaciers
15,000 years
residence time of groundwater
up to 10,000 years
residence time of rivers and lakes
2 weeks to 10 years
residence time of soil moisture
2-50 weeks
residence time of atmospheric moisture
10 days
residence time of biological water (biosphere)
1 week
what type of system is the hydrological cycle
a closed system
what type of cycle is the drainage basin
an open system
what is the global water budget
the annual balance of water fluxes (flows) and the size of the water stores.
is water a renewable or non renewable resource
Water stores have different residence times (amount of time the water is held for) but it is generally considered a renewable resource.
There is only one type of water which is the exception- Fossil water. This is water which has been held in an undisturbed space e.g aquifers for millennia. If this was to be used, there is little or no recharge of this store so it is considered a non-renewable resource. There are many aquifers and fossil water stores beneath the Sahara desert
what % of total global water is from oceans
96.5%
what % of freshwater is from groundwater
30.1%
what % of freshwater is from glaciers and ice caps
68.7%
what % of surface water and other freshwater is from ground ice and permafrost
69%
what % of surface water and other freshwater is from lakes
20.9%
how does the water budget limit water available for human consumption
fossil water
cryosphere losses
fossil water
untapped ancient stores of freshwater that exists in the polar regions and beneath deserts in the form of aquifers.
Once it’s used, there is little to no significant recharge, effectively making it non-renewable.
eg of fossil water
E.g. Kenya’s Lotikipi aquifer contains an estimated 200 billion cubic metres of freshwater.
cryosphere losses
Major ice sheets store water for very long periods (such as Antarctica and Greenland).
Ice core dating has suggested that the residence time of some water in the Antarctic ice is over 800,000 years.
69% is locked up in snowflakes, ice sheets/caps and glaciers found in high latitudes and high-altitude locations – this water supply is largely inaccessible to humans.
what are the two processes that drive the hydrological cycle
solar energy
gravitational potential energy
solar energy
This is when energy from the sun heats water and causes evaporation/transpiration.
More evaporation occurs as the global climate warms, which increase moisture levels in the atmosphere.
This in turn can lead to increased condensation as air cools, and therefore greater precipitation.
gravitational potential energy
This keeps water accelerating through the system under gravity
On land, energy is converted into kinetic energy as the water moves through the system by plant interception, or over land surface run-off.
where is solar energy concentrated
in the Tropics, where much is absorbed by the sea.
This evaporation produces high rainfall (74% of the world’s rainfall occurs at sea most within the Tropics). The rest is unevenly distributed e.g. the seasonal monsoons and droughts of Asia and Africa contrast with the temperature climates of North West Europe.
what do different climatic regions vary in
the nature and size of their inputs, transfers and flows of water.
how does solar energy affect polar regions and tropical rainforests
there is polar hydrology and tropical rainforest hydrology
how do seasons vary for polar hydrology
there are freeze thaw seasonal differences
how do seasons vary for tropical rainforest hydrology
few seasonal differences
effect of winter in polar hydrology
winter snow insulates the ground and 85% of solar radiation is reflected
effect of dense vegetation in tropical rainforest hydrology
dense vegetation intercepts and consumes up to 75% of precipitation
charachteristics of places with polar hydrology
lakes and rivers are frozen
limited vegetation cover reduces heat absorption
spring thaw causes rapid run off
summer thaw produces surface run off, increasing evaporation tenfold
freeze thaw cycle causes seasonal release of biogenic gases(caused by plant decomposition) into the atmosphere as well as carbon and nutrients into rivers and seas
annual precipitation of polar hydrology
less than 200mm
what type of rain is polar hydrology charachterized by
orographic or frontal precipitation and low humidity
charachteristics of tropical rainforest hydrology
50-75% of precipitation returns by evapotranspiration
evapotranspiration cools the air as energy is used during the process
rainforests generate their own rain, most is recycles within the tropics
less than 25% of rainfall reaches rivers or other surface water
there is limited surface infiltration or groundwater
rainforests are ‘cloud factories’
deforestation reduces evaporation- in turn reducing vapour and local rainfall
constant high temperatures
annual precipitation in tropical rainforest hydrology
over 2000 mm
what type of rainfall is tropical rainforest hydrology charachterised by
convectional rainfall and high humidity
what two types of water are exceptions to water being a renewable resource
fossil water
cryosphere losses
drainage basin system
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 within the basin to vary over time.
drainage basin definition
the area of land drained by a river and its tributaries. This area can also be referred to as the rivers catchment area.
precipitation definition
any form of water falling from the sky
watershed definition
the boundary of a drainage basin. This is usually a ridge of high land which divides and separated the water flowing into different rivers.
interception loss definition
this occurs when water is intercepted by vegetation and retained by the plant- the water will never reach the ground.
factors which effect basin flows/fluxes
forestry
relief/topography
flooding
input of rainfall
farming
vegetation
interception
infiltration and through flow
urbanisation
geology and soils
overland flow
percolation and groundwater flow
climate
evaporation and transpiration
what 3 things must be present for rainfall to be created
Air that is cooled to saturation point with a humidity of 100%
Condensation nuclei, such as dust particles to facilitate the growth of water droplets in clouds
A temperature below dew point (the temperature at which dew forms
what are the 3 types of rainfall
convectional
cyclonic/frontal
orographic
what are the 3 main types of interception
interception loss
through fall
stem flow
interception loss
water retained by a plant
through fall
when water drops from the leaves
stem flow
when water trickles along branches, twigs and the stem/trunk
what is infiltration
the process by which water soaks into the soil
what is infiltration capacity
The infiltration capacity is the maximum rate at which rain can be absorbed by soil
what does the rate of infiltration depend on
The infiltration capacity will decrease in time throughout a period of rainfall
The rate of infiltration depends on the amount of water already in the soil
Soil texture- sandy soils have a greater capacity than clay soils
Vegetation cover which varies throughout the year
Soil surface- compacted soils will have a reduced capacity
Slope/ topography- steep slopes encourage overland flow, smaller gradients encourage infiltration
what s through flow
the lateral transfer of water down slope through percolines (lines of water flow between layers of soil)
what is percolation
Percolation is the vertical movement, groundwater flow the lateral movement.
evaporation
Physical process by which moisture is lost into the atmosphere. It is a direct result of insolation (heat and light energy from the sun)
what factors determine rate of evaporation
Hours of sunlight
Temperature
Humidity
Wind speed
Size and depth of water
Vegetation cover
Surface colour
what is transpiration
Water lost through plants through their pores (stomata).
evapotranspiration (EVT)
Combined effect of evaporation and transpiration
potential evapotranspiration (PEVT)
The water loss which would occur if there was an unlimited amount of water in the soil for use by vegetation
what physical factors influence the drainage basin
rainfall
interception
infiltration and through flow
overland flow
percolation and groundwater flow
evaporation and transpiration
what are the main physical features that affect the drainage basin
climate
soils
geology
relief
vegetation
impacts of human actvivity on precipitation- affecting water basins
Human seeding of rainfall. Silver iodine pellets or ammonium nitrate are sent up into the sky to act as condensation nuclei to attract water droplets which will lead to increased rainfall in drought stricken areas. It has variable results.
how does cloud seeding work
1- silver iodide is released by a plane or ground based genorator
2- silver iodide particles reach the targeted cloud
3- the silver iodide aids in the formationof ice chrystals
4- ice chrystals become large enough to fall and create snow
eg of cloud seeding
ABU DHABI // Daily cloud seeding by the National Centre of Meteorology and Seismology may have increased the amount of rain across the country. The national weather bureau said it had launched about 20 rain-boosting flights since Thursday to blast hygroscopic salt, which attracts and holds water, into the clouds to try to produce more moisture.
what did studies conducted between 2002 and 2006 in abu dahbi suggest
rain enhancement programme could increase rain between 10 and 30%
effect of deforestation on evaporation and evapotranspiration
Deforestation would decrease the rate of evaporation and evapotranspiration, for example in the Amazon Rainforest, Brazil
effect of damn construction on evaporation and evapotranspiration
Reservoirs and dams, for example the Aswan Dam in Egypt will increase evaporation and evapotranspiration
effect of channelisation on evaporation and evapotranspiration
Channelization of rivers cuts down surface storage and so would reduce evaporation
effect of deforestation on interception
less evapotranspiration would lead to more surface run off. This would increase the chances of flooding and decrease lag time between peak rainfall and peak discharge in a river (volume of water in a river). This is a large issue in the Himalayas, Nepal
effect of afforestation on interception
should increase evapotranspiration and lengthen lag time which would prevent flooding. This has been seen in Plynlimon, Wales which is the source of the River Severn
how many times greater is infiltration under forests than grasslands
5 times
effect of farming/deforestationon infiltration
When deforestation occurs for farming there is les interception, more soil compaction and so less infiltration. However, some farming practices such as ploughing, increases infiltration rates as soil is made less compacts. E.g. in the foothills of the Himalayas , Nepal
effect of human activity on groundwater supplies
Human use of groundwater for irrigation or industry has lead to huge reductions in groundwater. For example the Aral sea which is between Kazakhstan and Uzbekistan began to shrink in 1960 as a result of over abstraction for the cotton industry. By 1994 the volume of water had reduced by 75%
what are many british cities doing in terms of groundwater
Conversely, in many British cities are reducing abstraction of groundwater used in industry and are now finding levels are starting to rise and causes issues for underground transport such as in London as well as many households finding their cellars are flooding more regularly.
effect of damn construction on water basins
Dams increase surface water stores and increase evaporation rates. They also reduce the discharge of the river downstream. Lake Nasser behind the Aswan Dam in Egypt is estimated to have evaporation losses of up to 16 billion cubic metres every year- that is 30 % of the water volume from the river Nile
effect of urbanisation on drainage basins
Impermeable surfaces reduce infiltration and increase surface run off and through flow through artificial drains. Reduced lag time and increases the risk of flooding and the discharge of rivers and streams. Flooding has become more apparent in many cities across the UK e.g York floods of 2015.
what does the water budget show
the annual balance between inputs and outputs
what does the water budget help to identify
The water budget helps to identify periods of time where there is a positive water budget (when precipitation would exceed evapotranspiration) and we would have a water surplus. OR identify a negative balance when evapotranspiration would be larger than precipitation and we would experience water scarcity and have an increased drought risk.
water balance equation
Precipitation (P)= channel discharge (Q) + evapotranspiration (E) +/- change in storage (S)
whats a soil moisture budget
It reflects the annual changes in precipitation and evapotranspiration and allows assessment of the soil moisture availability.
soil moisture deficiency
Soil water store has been used up. Plants will only survive if they have adaptations to survive periods of drought or they are irrigated.
soil moisture surplus
Precipitation greater than evapotranspiration. Run off recharges groundwater supply- the soil is at field capacity.
what will happen at the maximum annual temperature
River levels will fall, crops will need irrigation.
soil moisture utilisation
Evapotranspiration is exceeds precipitation. Water is being drawn up through the soil by capillary action- the water is being used up.
field capacity
. When the soil store is at full capacity and cannot hold anymore.