Water Security Flashcards
Define water security
Obtaining and managing sufficient water of a high enough quality ton meet current and likely future needs, without compromising activities and/or the environment
Give the 3 aspects of water security
Social - clean/healthy to drink
Economy - Affordable + sufficient for industrial activities
Environmental - Must not contaminate natural systems
…/10 households worldwide lack water security
3/10
What percentage of water is in the oceans
- 5%
2. 5% = freshwater
What percentage of freshwater is easily accessible
1%
What is the largest source of accessible freshwater
Lakes - 52%
Give 7 sources of water
River abstraction
Reservoir
Borehole
Pumping from aquifers
Glacial meltwater
Desalination
Recycled
Describe River abstraction
Oldest way humans have obtained water
Thames water (serving London + southeast) obtains 70% of its water from rivers
Describe Reservoirs as a water source
Storage lakes (Man-made/natural) that hold quantities of river flow such that it is subject to less short term fluctuations than a river level
Describe boreholes
Traditional walls are sunk through permeable surface layers to penetrate the water table contained in rock structures with water-holding capacity
Thames water = 30% water this way
Describe pumping from aquifers
An aquifer is a confined layer of saturated rock, usually deeper than the water table, and capped top and bottom by impermeable rock
When it is bored into, the substantial pressure forces the water to rise
Describe glacial meltwater
60% Iran’s freshwater comes from melting glaciers
Climate change poses serious issues for the medium term sustainability of this water source
The meltwater form glaciers in the Himalayas supplements several great rivers, such as the Ganges and Indus
Describe desalination
The evaporation of seawater to distil freshwater requires substantial energy input and produces salt as a by product
Modern plants use reverse osmosis
Israel gets 40% freshwater form desalination
Describe recycled water as a water source
As demand for freshwater intensifies, it is increasingly being recycled
In the valley of Mexico, approximately 90% of irrigation is resumed water form Mexico City
Define water surplus
Having more water than is needed
E.g - Wales - net exporter of water to England
Define water stress
Water supply periodically compromised
Occurs when there is less than 1700m³ litres available per person per year
May arise due to growing population demand, reduced water supply, or contamination of water supply
Define water scarcity
Insuffiecnt water to meet all human demands
Occurs when their is less than 1000m³ litres available per person per year
20% world’s population experience this and are forced to use water of poorer quality/use less
Define water crises
People don’t have access to potable water of sufficient quality or quantity to meet basic needs
Consequences =
- Human health deteriorates due to using contaminated sources
- Disease spreads due to unsatisfactory sanitary conditions
- Social disruptions as many hours each day dedicated to obtaining water
Where is the world’s most water stressed area
Middle East
Averages 1200m³ water per person/year
Describe Singapore water situation
High potential for water stress as demand exceeds natural supply
However, does not mean hat there is water scarcity as Singapore is an exceptional water manager
- Technology
- International agreements
- Management
- Rainfall capture systems
- Desalination plants
Give some physical factors that influence water supply
- Climate determines the global distribution fo water supply by means of annual and seasonal distribution of precipitation
- Precipitation varies globally, not only in terms of amounts, but also seal ditrabuton, availability and reliability
How does climate affect water supply
Precipitation is the paramount factor influencing water supply at a global scale. The average amount is around 860mm / year but this can vary greatly
Temperatures also influence rates of evaporation. High temperatures and intense sunshine can evaporate considerable amounts from the surface of water bodies, e.g. Lakes and river
How does geology affect water supply
Geology controls the distribution of aquifers that provide groundwater storage
Some rocks (e.g. Chalk) are permeable and can provide groundwater supplies. Impermeable lithology is more likely to generate surface flow in the form of streams and rivers.
Aquifers usually form in sedimentary basins, subject to variable layers of permeable and impermeable rock
How does drainage and relief affect water supply
River systems and surface water (drainage) are a function of climate, relief, vegetation and geology
Gentle relief allows more time for water to infiltrate and contribute to groundwater. It is also more likely to lead to natural lakes. Steep relief generates faster flows.
Natural vegetation can also influence drainage: by intercepting rainfall, impeding surface flows or absorbing water via root systems.
Give an example of climate affecting water supply
The record high for average annual rainfall is at Mt Waialeale in Hawaii at 114,000 mm whereas the record lowest is in the Atacama desert in Chile, where no rain fell for 14 years
Give an example of geology affecting water supply
Greater London draws on water from the chalk aquifer beneath it. This is recharged by rainfall falling on the North Downs and Chiltern Hills.
Give an example of drainage and relief affecting water supply
The Amazon has an average discharge of 175,000 m3/sec from its catchment area of 6,915,000 km2. It generates its own microclimate through massive evapotranspiration that seeds more precipitation on route.
