5.7 Flashcards
What is water scarcity
Water scarcity can either be a physical scarcity (insufficient water supply to meet demand)
-There can also be economic scarcity ( where water is unaffordable, even with availability
- It is classed as when water availability falls below 1000m3 per person per year
- It can threaten food supplies, reduce economic development and cause environmental damage
What is water stress
- water stress is when a country’s water consumption exceeds 10% of its renewable freshwater supply (including difficulty obtaining new water quantities and poor water quality restricting usage)
- It is defined as when water falls below 1700m3 per person per year
What is water insecurity
- water insecurity is the combination of water stress and scarcity, where present and future supplies of water can’t be guaranteed
- It leads to a need for physical,political or economic solutions (e.g dam building, supply agreements)
What are the different levels of water stress and scarcity
Regular water stress -> less than1700m3 per capita / year (including South Africa, Somalia, Poland and Cyprus )
Chronic water scarcity -> less than 1000m3 per capita/ year (including Kenya, Rwanda and Cape Verde)
Absolute water scarcity -> less than 500m3 per capita/ year (eg Kuwait)
What were the UN findings on water scarcity
- Water scarcity (physical) affects 1.2 billion people (500 million more approaching )
- water scarcity (economic) affects 1.6 billion people
- Water scarcity is predicted to be one of the main issues facing society in the 21st century
- It is both a natural and man made phenomenon
What is the pattern for water insecurity
- water insecurity is mainly distributed across the equator and northern hemisphere desert regions
- moderate scarcity is present on the periphery of scarce regions
- Economic stress generally distracted in the Southern Hemisphere and equatorial regions (between the tropics)
- This does not correlate entirely with physical water stress distribution
How do you calculate water availability
Water availability = supply - demand +/- competition in basin
What is happening to water availability
- There is an increasing mismatch between water supply and demand creating insecurity
- The amount of freshwater in the global hydrological cycle is finite, but 60% of worlds accessible freshwater is being used
- There is another mismatch between where water is available and where water demand is (66% of the population lives in areas with 25% of worlds Annual rainfall
- There is a widening availability gap due to rising demands and diminishing supplies ( mainly due to overexploitation of groundwater for irrigation
- This gap means the world is becoming divided between developing countries and developed countries
How can climate variability cause water insecurity (physical)
- Global variations in freshwater resources are caused by natural climate variability (due to atmospheric pressure systems )
- increasing variability in precipitation patterns leading to direct and indirect effects in the whole hydrological cycle
- Short term climate changes (due to enso cycles) can exacerbate the water security situation of a place
- Longer term climate changes (due to global warming) are causing increasing variability in climate systems
- On a regional scale , physical topography and continentality can also promote or demote climate variability which affects water insecurity
How can geology cause water insecurity (physical)
- Geology controls the distribution of aquifers (water bearing rocks) which provide groundwater storage
- Permeable and porous rocks can store water ( valuable as not subject to evaporation loss) which can then be accessed through springs and wells (providing supply despite uneven distribution as long as not overused)
- Over abstraction from these sources can however combine to lead to insecurity
How is saltwater encroachment causing water insecurity (physical)
- The seaward movement of freshwater usually stops salt intrusion ,but due to loss of flow and global sea level rise , saltwater intrusion has increased
- Extensive groundwater extraction lowers the water table which allows salt water to move into the soils
- thermal expansion of the sea and eustatic sea level rise due to global warming enable saltwater to intrude inland, polluting soil moisture and groundwater stores
- This saltwater encroachment threatens farming (dependent on freshwater irrigation) , health (saltwater consumption) and natural ecosystems and biodivetusu
- This will increase insecurity and put pressure to create methods of mitigation
How are changes to water stores increasing water insecurity (physical)
- Water stores are being affected by a variety of factors increasing water insecurity
- Warmer water encourage the growth of bacteria and other organisms which negatively affect health
- Water may also be affected by sedimentation, dissolved carbon, pesticides ect which all serve to reduce water quality
How can over abstraction lead to water insecurity
- Over abstraction occurs when too much water is removed from groundwater and so supplies diminish
- An estimated 20% of the worlds aquifers are being over exploited e.g north china plain, Bangladesh
How is agriculture contributing to water insecurity (human)
Agriculture is the largest user of water (70% of usage in some developing countries) + there is an increasing requirement with global agriculture needing to produce 60% more food to meet the demands of the growing population
- Inefficient use of water for crop production is depleting aquifers, reducing river flow, degrading wildlife habitats, increasing pesticide pollution, water logging and increasing salinity
- 20% of the worlds irrigated land now suffers from salinity
- chemical fertilisers have recently caused pollution as seepage into groundwater supplies creates contamination
How is energy increasing water insecurity (human)
- The energy industry requires increasing amounts of water for new developments
- technological efficiency advancements are available but the damage has been done due to a finite source
- HEP dams now impede over 60% of the worlds major rivers damaging sediment movement processes and leaving to damaged water cycles that create insecurity
- Increased energy demands also requires more water for power station processes (e.g cooling water)
