The Water Cycle and Water Insecurity Flashcards
Flux
the rate of flow between stores
Systems approach
Studying hydrological phenomena by looking at the balance of inputs and outputs, and how water is moved between stores by flows
Cryosphere
Areas of the Earth where water is frozen into snow and ice
Open system
- have transfers of energy and matter beyond and into the boundaries
Closed system
- have transfers of energy beyond the boundaries but not matter
dynamic equilibrium
when there is a balance between the inputs and outputs of a system, so matter stored in the system is constant
The global hydrological cycle
- closed system
- driven by solar energy (input) and gravitational potential energy
- the amount of water is constant on Earth and in the atmosphere
- proportions of different forms of water can change over time (solid, liquid and gas)
What flows/processes are there inside a hydrological system
- surface runoff
- groundwater flows
- channel flows
- precipitation
- evapotranspiration
- interception
- percolation
What stores are there inside a hydrological cycle
- atmosphere
- hydrosphere
- cryosphere
- biosphere
- lithosphere
Where is the Earth’s water stored?
- 96.5% stored in ocean
- 2.5% of the world’s water is surface and groundwater freshwater
- very little of this freshwater is accessible, with the majority of it stored as ice-caps
drainage basin system
- an area of land drained by a river and its tributaries
- is an open system so the amount of water in the drainage basin system varies over time
structures within a drainage basin
- main river
- tributaries
- watershed ( high land around the edge of the basin)
- catchment area (whole basin)
- source (start)
- mouth (end)
- confluence (two rivers join)
Blue water
water stored in rivers, streams or 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)
Precipitation and the conditions required for it
- the movement of water in any form from the atmosphere to the ground
- air cooled to saturation point 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
Evaporation
the change of state of water from a liquid to a gas
Transpiration
the diffusion of water from vegetation into the atmosphere involving a change from a liquid to a gas
surface storage
the storage of water on the ground’s surface
soil storage
the storage of water in the soil
groundwater storage
the storage of water underground that has percolated through porous rocks
channel storage
the storage of water in streams or rivers
interception
water that is retained by vegetation surfaces from precipitation
infiltration
the movement of water from the ground to the soil
percolation
the transfer of water from the surface soil into the bedrock beneath
surface runoff
the movement of water that is unconfined by a channel across the surface of the ground
infiltration capacity
the maximum rate at which a soil is capable of absorbing water in a given condition
what factors determine infiltration capacity
- duration and intensity of rainfall
- surface gradient
- antecedent rainfall
- soil porosity
- compaction of the soil
- vegetation type and cover
subsurface throughflow
the lateral transfer of water downslope through the soil via natural pipes and percolines
potential evapotranspiration
the water loss that would occur is there was an unlimited supply of water (in the soil for use by vegetation) Distance between actual evapotranspiration rates and potential evapotranspiration is larger in arid areas
Interception capacity
the ability of the vegetation to store water in a given conditions
factors that determine interception capacity
- vegetation type and cover
- season
- duration and intensity of rainfall
- land use (natural, agricultural, urban)
Convectional rainfall
- common in tropical areas or in the summer in the UK
- often associated with intense thunderstorms
- the sun heats the land, making the air above it become warmer
- the air rises and expands
- as it rises, the air cools and its ability to hold water vapour decreases, creating convection currents
- condensation occurs and clouds develop
- if air continues to rise, rain will fall
Orographic rainfall and rain shadows
- warm, moist air from the oceans rises up over mountains
- when it rises it cools and condenses to form clouds, bringing rain
- once the air has passed over the mountain it descends and warms
- this creates drier conditions at the leeward end of the mountain known as a rain shadow
Cyclonic/frontal rainfall
- when a warm front meets a cold front
- the heavier cold air sinks to the ground so the warm air is forced to rise above it
- when the warm air rises, it cools and its ability to hold water vapour decreases
- condensation occurs, forming clouds which bring heavy rain
Physical factors that influence the drainage basin cycle
- climate
- soils
- geology
- relief
- vegetation
How does climate influence the drainage basin cycle
Has a role in influencing the type and amount of precipitation overall and the amount of evapotranspiration
Has an indirect impact on the vegetation type
How does soil influence the drainage basin cycle
Determines the amount of filtration and throughflow (dependent on porosity and compactness)
Indirectly influences the type of vegetation
How does geology influence the drainage basin cycle
can impact of subsurface processes such as percolation and groundwater flow, so also impacts aquifers
Indirectly alters soil formation
How can relief influence the drainage basin cycle
Altitude can impact on precipitation totals
Slopes can affect the amount of runoff
How can vegetation influence the drainage basin cycle
The presence or absence of vegetation impacts on the amount of interception , infiltration and occurrence of overland flow as well as transpiration rates
Human impact on precipitation
- pollution can provide condensation nuclei
- cloud seeding = the introduction of silver iodide pellets or ammonium nitrate to act as condensation nuclei to attract water droplets and increase rainfall in drought-stricken rainfall. It has variable results
Human impact of evapotranspiration
- changes in global land use especially through deforestation
- increased potential evaporation resulting from artificial reservoirs behind mega dams
- channelisation of rivers in urban areas into conduits cuts down surface storage and therefore evaporation
Human impact on interception
- deforestation and afforestation
- deforestation leads to a reduction in evapotranspiration and an increase in surface runoff, increasing flooding potential and decreases lag time (speeds up the cycle)
- after the planting of young trees there is a period of time where there is an increase in runoff due to earth compaction by planting equipment
Human impact on infiltration and soil water
- conversion of forest to grassland/farmland decreases infiltration
- farmland and grazing animals also increase soil compaction which increases overland flow
Human impact on groundwater
- human use of irrigation for extensive cereal farming has led to declining water table in areas such as the Aral Sea
- recent reductions in groundwater abstraction in British cities have led to flooding of basements and cellars, surface water flooding and leaking into tunnels such as the London Underground as groundwater rises. The water supplies are also more likely to become more polluted
Replacement of vegetated soils with impermeable surfaces (urbanisation)
- increases runoff as the ground is impermeable. Infiltration and percolation decreases
- high density of buildings means that rain falls on to roofs and then is swiftly dispatched into drains by gutters and pipes, reducing storage capacity and lag time
- piles of dumped soil from building activity increases sediment in soils
- interception decreases as there is less vegetation
Encroachment on the river channel (urbanisation)
- urban rivers tend to be channelised with embankments
- reclamation and riverside roads also decrease the width of the river channel
- floods can be more devastating because of the restricted river
- bridges can restrain discharge and act as dams, increasing water levels upstream
Pollution control problems (urbanisation)
- storm water washing off roads and roofs can contain heavy metals, volatile solids and organic chemicals
Water resource problems in urban areas
- sewers do not allow for percolation so groundwater that has been extracted cannot be replaced
Water balance/budget
- the balance between inputs and outputs (precipitation, evapotranspiration and runoff)
- can be useful at global, regional and local scales
- can be shown using the formula
precipitation = streamflow + evapotranspiration +/- changes in storage
P = Q + E +/- S
Seasonal patterns in the general water balance of the UK
- In Autumn and Winter, precipitation is greater than evapotranspiration, creating a water surplus
- ground stores fill with water which leads to increased surface runoff, higher discharge and higher river levels. There is a positive water balance
- in the Summer, evapotranspiration exceeds precipitation
- as plants absorb water, ground stores are depleted leading to a water deficit at the end of the season
River regime
the annual variation of discharge or flow of a river at a particular point or gauging station. Usually measured in cumecs
What is the character of the river regime influenced by
- the geology and overlying soils, their porosity and permeability. Water stored as groundwater in permeable rocks is gradually released into the river as base flow which regulates the flow during dry periods
- temperatures experienced
- the size of the river basin and where measurements are taken
- the amount, pattern and intensity of precipitation
- amount and type of vegetation cover
- human activities that regulate the flow
Rising limb
the part on a storm hydrograph in which the river begins to rise
peak discharge
the time when the river reaches its highest flow
lag time
the interval between peak rainfall and peak discharge
falling/recessional limb
the part of a storm hydrograph in which the discharge starts to decrease
base flow
the normal day-to-day discharge of the river
storm hydrograph
a graph that shows the variation of river discharge within a short period of time. Shows how a drainage basin responds to a period of rainfall
Factors that lead to a ‘flashy river’ (short lag time, high peak, steep rising limb)
- intense storm which exceeds the infiltration capacity of the soil
- rapid snow melt as temperatures suddenly rise above freezing
- low evaporation rates due to low temperatures
- impermeable rocks
- soils with a low infiltration rate (clays)
- high steep slopes
- small basin size
- high drainage density (high density of streams and rivers)
- low density vegetation, deciduous in winter
- wet antecedent conditions, soil saturated, water table high
- urbanisation, deforestation, downslope ploughing
factors that lead to a ‘flat’ river (long lag time, low peak, gently sloping rising limb)
- steady rainfall, slow snow melt as temperature gradually rises, high temperatures so high evaporation rates
- permeable rocks
- soils with a high infiltration rate (sandy)
- low, gentle slopes
- larger basins
- circular basins
- low drainage density (low density of streams and rivers)
- dense vegetation, deciduous in summer
- dry antecedent conditions, low water table, unsaturated soils
- low population density, few impermeable artificial surfaces, reforestation, moorland, pastoral and forested land
meteorological drought definition
rainfall deficit as a result of short-term variability or longer-term trends which increase the duration of the dry period. Often occurs in arid and semi-arid regions.
The shortest duration and least severe drought.
features of a meteorological drought
- low rainfall
- high temperatures
- strong winds
- increased solar radiation
- reduced snow cover
major impacts on a meteorological drought
- loss of soil moisture
- supply of irrigation water declines
What can cause rainfall deficiency
- natural variations
- desiccation caused by deforestation
- longer term trends e.g. climate change
hydrological drought definition
associated with reduced streamflow and groundwater which decrease due to reduced inputs of precipitation and continued high rates of evaporation
major features of a hydrological drought
stream flow deficit
- reduced infiltration
- low soil moisture
- little percolation and groundwater recharge
major impacts of a hydrological drought
- reduced storage in lakes and reservoirs
- less water for urban supply and power generation - restrictions
- poorer water quality and salinisation
- threats to wetlands and wildlife habitats
Agricultural drought definition
Deficiency of soil moisture and soil water availability due to the rainfall deficiency from meteorological drought. Has a knock on effect on plant growth and reduces biomass. Often accelerated by farming practices such as overgrazing
major features of an agricultural drought
Soil moisture deficit
- low evapotranspiration
- plant water stress
- reduced biomass
- fall in groundwater levels
major impacts of an agricultural drought
- poor yields from rain-fed crops
- irrigation systems start to fail
- pasture and livestock productivity declines
- rural industries affected
- some government aid required
famine drought definition
The manifestation of meteorological, hydrological and agricultural drought. A humanitarian crisis with severe social, economic and environmental impacts. The widespread failure of the agricultural system leads to food shortages and famines.
major features of a famine drought
Food deficit
- loss of natural vegetation
- increased risk of wildfires
- wind blown soil erosion
- desertification
major impacts of a famine drought
- widespread failure of agricultural systems
- food shortages on seasonal scale
- rural economy collapses
- rural-urban migration
- increased malnutrition related mortality
- humanitarian crisis
- international aid required
Palmer Drought Severity Index (PDSI)
- applies to long-term drought and uses current data as well as that of the preceding months as drought is dependent on previous conditions
- focuses on monitoring the duration and intensity of large scale, long-term, drought-inducing atmospheric circulation
Crop Moisture Index (CMI)
- a measure of short term drought on a weekly scale
- useful for farmers to monitor water availability during the drought season
Why are some areas more vulnerable to drought?
- link between droughts and some climate patterns
- high-pressure systems reduce evaporation and moisture in the atmosphere, leading to less precipitation (at the tropics)
- El Nino creates droughts in Indonesia and Australia
- La Nina creates droughts in in North and South America
Human activities that can cause drought
- irrigation in agriculture
- soil degradation through intensive farming and deforestation
- dam building
- deforestation
- increased demand for water
- climate change
hazardous impacts of droughts
- lack of clean and reliable water supply
- water borne diseases
- high crop and livestock losses
- famine experienced by subsistence farmers
- wildfires
- conflicts when pressure is put on water supplies
bank full discharge
the river has reached its full capacity
flooding
occurs when discharge is higher than a rivers bank full discharge and the river bursts its banks and overflows onto the surrounding land
human causes of river flooding
- Urbanisation - impermeable surfaces, diverting water away from cities can lead to flooding in other areas
- deforestation
- increased population density, building on floodplains
- farming practices
- crops
- overgrazing
meteorological causes of flooding
- a lot of precipitation over a short period of time (‘flashy’ hydrograph- usually in Summer)
- high amounts of precipitation over a long period of time (‘stretched’ hydrograph - usually in winter)
- snowmelt and icemelt upstream (sudden rise in temperature or seasonal)
climatological causes of drought
human induced accelerated climate change have increased the frequency and intensity of storms that bring flooding
The El Nino Southern Oscillation (ENSO)
- usually occurs every 3-7 years and lasts for 18 months
- the trade winds across the tropical Pacific weakens and dies
or reverses - the piled-up water in the West moves East, leading to a sea level rise in Peru
- the cold water on the coast of Peru is replaced with warm water
- rainfall increases dramatically in Ecuador and Peru, causing coastal flooding and increased erosion
- droughts in Australia and Indonesia
- warmer air spreads further and releases more heat into the atmosphere, global temperatures increase
A normal/ non El Nino year
- the trade winds blow westwards across the tropical Pacific
A normal/ non El Nino year
- the trade winds blow westwards across the tropical Pacific from Peru to Australia
- the winds push warm air westward
- along the east coast of Peru, the wind brings up cold water to replace the water blown westward (upwelling)
- sea levels and temperatures are higher in Australasia that Peru
- rainforests in Australasia because warm, moist air rises, cools and condenses, forming clouds
- cold, dry air is returned to Peru (Walker loop)
La Nina
- usually follows El Nino
- an exaggerated version of a normal year, with a strong Walker loop
- extremely strong Westward trade winds
- sea levels rise a lot in Indonesia
- heavy rainfall in South East Asia
- very high pressure and extreme drought in Peru
The effect of climate change on El Nino
- increased frequency of extreme El Nino events
- detectable by 2030
- warming of the Eastern Pacific ocean by climate change will cause stronger El Nino events
- more droughts in Australasia and rain in Peru
- often followed by strong prolonged El Ninas
Effects of strong El Ninos
- human health, food productions, economies and energy and water supply all over the world is affected
- upwelling around Peru in normal conditions creates nutrient-rich water with lots of plankton, providing food for a large variety of fish
- El Nino means fish populations die or migrate
Teleconnection
climate anomalies which relate to each other at large distances e.g. ENSO
Desertification
land degradation in arid, semi-arid and dry sub-humid conditions resulting from climatic variations or human activities
Why are wetlands important globally?
- act as temporary water stores , mitigating river floods downstream, protecting land from erosions, recharging aquifers
- act as water filters, trapping and recycling nutrients and pollutants
- high biological productivity and diversity
groundwater flooding
flooding that occurs after the ground has become saturated from prolonged heavy rainfall. low lying floodplains and river estuaries are most at risk
surface water flooding
flooding that occurs when intense rainfall has insufficient time to infiltrate the soil, so flows overland. low lying areas that are partially urbanised with impermeable surfaces are most at risk
Flask flooding
a flood with an exceptionally short lag time, often minutes or hours. Small basins in arid or semi-arid areas are especially at risk and they are extremely dangerous
socio-economic impacts of flooding
- morbidity from drowning or poisonous snakes in the water
- post-flood morbidity in LICs from water-borne diseases
- psychological stress
- direct structural damage to properties affects livelihoods
- crops, livestock and agricultural infrastructure suffer major damage in intensively farmed rural areas
- drop in tourism
- substantial infrastructure losses in megacities such as Mumbai
Environmental impacts of flooding
- recharge groundwater systems
- fill wetlands
- increase connectivity between aquatic habitats
- move sediment and nutrients around the landscape and into marine environments
-trigger breeding, migration and dispersal of some species - eutrophication and soil pollution in areas degraded by human activity
How does climate change impact the hydrological cycle
- wet and dry extremes and the general variability of the water cycle will increase but not uniformly around the globe
- rainfall intensity is expected to increase for most land areas
- increased dryness expected in the Mediterranean and western N&S America
- reduction in mountain glaciers, snow cover, earlier snowmelt, changes in monsoon rates
- causes parts of the water cycle to speed up as warming temperatures = more evaporation = more precipitation
- increased CO2 may speed plant growth so increase transpirations
- stronger hurricanes due to warmer ocean surfaces
resource security
when there is enough resources go go around a region or country. supply is greater than demand
resource insecurity
when there is not enough resources to go around in a region or country. Demand is greater than supply.
3 factors affecting water security
- physical distribution
uneven supply of precipitation meaning some areas of the world have supply issues and water insecurity - the gap between supply and demand
an increase in demand or a decrease in supply can cause insecurity - water availability
inequality between HICs/MEDCs and LICs/LEDCs
factors behind the rising demand for water
- population growth
the majority of population growth is in urban areas in the developing world that have existing water insecurities - development and economic growth
industrialisation has led to water demands growing in all sectors - improving standards of living
higher consumption of water through domestic use (drinking, bathing, cleaning) and the mechanisation of consumer goods (dishwashers etc)
-farming practices
irrigation on a large scale, changing demands for a diet rich in dairy and meat - dwindling supply
over abstraction of water from reservoirs and groundwater aquifers leads to reduction in water storage within the hydrological cycle
virtual water
the hidden flow of water when food and other commodities are traded (water used to make commodities). it often flows in the direction of richer countries
common types of water pollution
- disposal of untreated pollution (causes water borne diseases)
- chemical fertilisers (eutrophication)
- industrial waste ( toxic heavy metals and chemical waste)
- dams impacting sediment movement (impacts river ecology)
water poverty index
- generally correlated with GNP
- 5 parameters scored out of 20
- environment
sustainability - access
time and distance involved in obtaining safe and sufficient water - use
how economically water is used - capacity
how well water is managed - resources
quantity and quality pp
UK water transfer scheme
- rainfall is mainly concentrated along the west coast of the UK due to relief and moist air from the coast
- population density is highest in the South East and West Midlands
- scheme transports water from areas of surplus to areas of deficit
west to east and rural to urban - the diversion of water from one drainage basin to another
- transferred from reservoirs through aqueducts and underground pipes
physical water scarcity
largely determined by climate (precipitation vs evapotranspiration), continentality (coastal or inland), topography
economic water scarcity
- associated with developing countries that lack capital, technology and good governance to fully exploit their water supply
e.g. Sub-Saharan Africa, Laos, Haiti
Green revolution
the use of high yield varieties (HYVs) of crops and agrochemicals and irrigation to increase yields and improve food supplies (1960s)
- highly water intensive
What is the price of water determined by
- physical cost of obtaining supply (if water has to be piped for many kilometers from mountain reservoirs)
- degree of demand of water
- insufficient infrastructure, the cost of water from informal street vendors is very high
- who supplies the water (the government, private water companies, private water companies subsidised by the government)
Structural Adjustment Programmes (SAPs)
- developed by the world bank and IMF
- claimed it would help developing countries overcome debt issues by putting in place neo-liberal policies
- privatised utilities including water
- seen as essential as systems were inefficient and corrupt
- in many countries it resulted in hardships and gave little progress in solution to debts
- gave contracts to European TNCs in hope of huge profits
- cost of providing water under difficult conditions meant large price increases, meaning the poor could not pay for water
Privatisation of water
- decision makers promote neo-liberal view in favor of privatisation of water, so subsidies end
- with private companies, water would be seen as a commodity from which profits can be made
- politicians assume privatisation will conserve water, improve efficiency and increase service quality and coverage
impacts of water insecurity
- lack of clean piped water
decrease of girls in education as they are collecting water - waterborne diseases
- lower levels of food production
- industrial output
areas unable to open factories and produce products due to large amount of water required. Have to rely on expensive imports - conflicts
water conflict
- when demand exceeds supply
- interrelated with boundary disputes
- mostly political but can lead to armed conflict
- shared groundwater of rivers flowing between international boundaries
top down water management
large scale schemes focusing on supply efficiency often disregarding the needs and wants of local people
bottom up water management
localised projects, often sustainable and NGO funded/implemented
water transfer issues for the source area
- drop in river flow so it becomes polluted and more saline, impacting the ecosystem
- climate change combined with lower flows can lead to water scarcity
water transfer issues for the receiving area
- grater availability of water simply leads to greater use
- increased use for development (e.g. golf courses, tourism)
- promotes unsustainable irrigated farming by agri-businesses
- nitrate eutrophication, salination and ecosystem destruction. Pollution transfer
mega dams
the 5,000 mega-dams in the world have the capacity to store 16% of the annual global water supply, but evaporation is very high because of the large surface area and many dams being located in semi-arid areas
- China is the world’s leading dam builder and is now building in Africa as part of its FDI program
- there is a push to produce clean energy through HEP
- developing countries have the sites and now have the means to build dams
desalination
- draws water supplies from the ocean
- conserves water supplies but has a massive ecological impact on marine life and is expensive
- new breakthroughs in technology have made desalination more cost efficient, less energy intensive and easier to implement on a larger scale
- fossil fuels are frequently used in the process so there is a large carbon footprint
- more viable than massive water transfer schemes
- dumping leftover water after the desalination near the shoreline will have an adverse consequences on coral reefs and their food webs as it has a high salt concentration
the water sustainability quadrant
- Futurity, ensuring security of supplies for the future while also managing demand
- Environment, achieving high standards of environmental protection and restoration
- Public participation, involvement of communities, NGOs and bottom-up solutions
- Equity and social justice, equitable allocation, affordable prices, good governance and management
water conservation
- manages demand and makes the use of water more efficient
- ‘more crop per drop’ in agriculture, more advanced drip irrigation systems and automated spray technology that uses less water, repairing leaks in irrigation systems
fossil water
- ancient deep groundwater from former pluvial (wetter) period
- is not renewable or reachable for human use
