Flashcards in ECOSYSTEMS L5- Water Scarcity Deck (24):
What is an arid region?
Arid regions are characterised by high rainfall variability.
They receive less than 250mm p/year.
0.17% out of 0.54 freshwater resources are found in arid regions- but this is distributed unevenly AND much of this water is not immediately accessible.
Groundwater is the world's most extracted resource
Why does the replenishment rate of groundwater vary?
1) land use change
2) changes in surface water
3) lowering of the water table
4) long term climatic cycles
Why does the quality of groundwater vary?
2) Contamination from inadequate sewage infrastructure
3) Natural contamination
E.g. Bangladesh's water supply is naturally contaminated with arsenic and fluoride.
What are the main problems in arid regions?
2) poor quality
4) limited potential for improving quality/quantity
BUT, addressing one of these issues may worsen another.
EXAMPLE- groundwater depletion in India
India abstracts more groundwater than he 2nd/3rd highest consumers combined.
In NW India, this has led to the depletion of aquifers- with western farming techniques largely to blame.
The abstraction rate is higher than the replenishment rate.
There is a decline of 1m p/year in the water table.
EXAMPLE- The Aral Sea
Water was diverted from the Amu-Darya and Syr-Darya for irrigation of water intensive crops by the Soviet Union.
Over 60% of water was lost over a period of 30 years.
This has creator poisonous levels of salinity.
Over 60 million people rely on the basin.
What is drought?
Drought is a natural and temporary phenomenon and is characterised as a deviation from normal conditions.
BUT there is no universal definition of drought.
The American Meteorological Society (1997)
Four different types of drought:
1) meteorological (precipitation deficit)
2) hydrological (sub-surface supply deficit)
3) agricultural (lack of soil moisture)
4) socio-economic (supply but can not access)
What is water scarcity?
A natural and human made phenomenon- it occurs when demand exceeds the natural available resources.
a) UN (2014)
"There is enough freshwater on the planet for 7 billion people, but it is distributed unevenly and much of it is wasted, polluted and unsustainably managed"
b) UN (2014)
1.2 billion people live in areas of physical water scarcity
1.6 billion people live in areas of economic water scarcity
What is water stress?
Water stress refers to the ability (or lack thereof) to meet human and ecological demands for water.
How many people are affected by water stress? (UN, 2014)
30 countries are considered to be under water stress- 20 under absolute scarcity.
Water stress can be alleviated in areas such as Syria and Jordan where water intensive commodities can be imported.
Environmental Agency (2007)
Parts of SE England have less water p/person than those in Sudan or Syria.
Example- water stress management in the EU
Policy is based on the principle of water hierarchy.
i.e. additional water supply infrastructure should only be considered when all demand measures have been exhausted.
Member states are encouraged to focus on prevention methods.
What is desertification?
Desertification means degradation of land and vegetation, soil erosion and infertile lands in arid areas.
It is causes primarily by human activities and climatic variation.
Van Loon (2016)
The HC is intertwined with human influence- we cannot separate the two.
Drought can be causes by physical or human influences.
Human impacts of the Earth's systems are increasing and this must be recognised as a new epoch (Anthropocene)
Humans actively shape water availability so we can no longer view drought as an external hazard.
This human influence must be made clear in drought definitions.
Houses of Parliament (2012)
Responses to water scarcity is mainly in the hands of private water companies and users.
The choice to increase demand is having a negative effect on ecosystems in freshwater bodies.
Drought in the UK occurs approximately every 7 years- areas with the highest populations often receive the lowest levels of rainfall.
Sheffield et al. (2012)
Drought is expected to increase in frequency and severity due to climate change.
Calculations using the Palmer Drought Severity Index have suggested that global moisture levels have been decreasing since 1970s.
BUT some have criticised this method as overestimating the increases in drought conditions- arguing that there has been little change in drought over the last 60 years.
The way we define or measure drought determines HOW we interpret the impacts of future climate change.
Example- The Klamath River, USA
Travels from South Oregon to California- this transboundary nature has produced multiple management disputes.
Farmers want to use the water for irrigation, while indigenous groups and environmentalists want to stop irrigation.
This tension heightens every summer when the waters dry up for 3 months.
Previously, management could not be adapted as water scarcity measurements were done on an annual basis. However, this is now done on a monthly scale so there is potential to decrease conflict.