lecture 2: use and availability Flashcards
What is the water footprint?
a measure of humanity’s appropriation of fresh water in volumes of water consumed and/or polluted.
it measures the amount of water used to produce each of the goods and services we use. it can be measured for a single process, such as growing rice, for a product, such as a pair of jeans, for the fuel we put in our car, or for an entire multi-national company.
- the water footprint can also tell us how much water is being consumed by a particular country- or globally- in a specific river basin or from an aquifer.
How can the water footprint be measured?
- cubic meters
- per tonne of production
- per hectare of cropland
- per unit of currency
- and in other functional units
the water footprint helps us understand for what purposes our limited freshwater resources are being consumed and polluted.
the impact it has depends on where the water is taken from and when
if it comes from a place where water is already scarce, the consequences can be significant and require action.
What is the green water footprint?
is the water from precipitation that is stored in the root zone of the soil and evaporated, transpired or incoproated by plants. it is particular relevant for agricultural, horticultural and forestry products
What is the blue water footprint?
is the water that has been sources from surface or groundwater resoures and is either evaporated, incoprotaed into a product or taken from one body of water and retruned to another, or returned at a different time. Irrigated agriculture, industry and domestic water use can each have a blue water footprint.
What is the grey water footprint?
is the amount of freshwater required to assimilate pollutants to meet specific water quality standards. The grey water footprint considers point-source pollution discharges to a freshwater resource directly through a pipe or indirectly through runoff or leaching from the soil, impervious surfaces, or other diffuse sources.
what substance uses the most amount of water?
Proteins
plus land and energy
- feedstock cultivation
- livestock farming
- food processor
- retailer
- consumer
(all have direct water footprints)
(it takes nine times as much water to produce 1kg of beef compared to that required to produce 1kg of chicken).
(synthetic rubber production is also very water consuming- 3000l/kg)
here are some examples of the global/ national crop water footprint?
Global crop water footprint Wc,g = Wc (m3/ton) x Pc,g (M tons/year) Global rice water footprint: Wrice,g = 2291 m3/ton x 593 M ton/yr = 1,358,563 M m3/yr = 1358 km3/yr Annual rice production in Thailand: Price,Thailand = 18 M tons Rice water footprint: Wrice,Thailand = 2291 m3/ton * 18 M tons = 41238 M m3/yr = 41 km3/yr Annual rainfall over Thailand, R = 1750 mm/yr Area of Thailand, A = 513,120 km² Volume of rainfall, V = R x A = 1750 / (1000*1000) x 513,120 = 898 km3/yr Wrice,Thailand = ~5% Total renewable water resources = 438 km3/yr Wrice,Thailand = ~10% Internal renewable water resources = 225 km3/yr Wrice,Thailand = ~20%
Water use depends not only on the application but also the location
Czech republic: calculated water footprint for litre of beer (45L)
SA: (155L)
The water footprint allows us to answer a broad range of questions for companies, governments and individuals
Where is the water dependence in my company’s
operations or supply chain?
How well are regulations protecting our water
resources?
How secure are our food or energy supplies?
Can I do something to reduce my own water footprint
and help us manage water for both people and nature?
UK domestic water use: where is potable water quality required?
- bath/ shower
- dishwasher
- drinking
define: internal renewable water resources
what is produced within a region
Define: external renewable water resources
what is produced outside of a region
define: total renewable water resources
internal + external
Dependency ratio
- percentage of total renewable water resources originating outside of countru = 100% x external/ total
what are the blue planet statistics?
- Total volume of water on Earth (100%) = 1,386,000,000 km3
- Total freshwater (2.5%) = 35,000,000 km3
- Available freshwater (0.015%) = 200,000 km3
what is the salt constraint?
saltwater 97%
freshwater 2.5%
glaciers and permenant snow cover 68.9%/ groundwater 30.8%, lakes and river storage 0.3%
what is the hydrological cycle residence time constraint
Residence time: average travel time for water to pass through a subsystem of the hydrologic cycle (e.g. river or aquifer)
Tr = S/ Q
Tr= residence time S= storage Q= flow rate- a function of natural flows and human management
Residence time dictates the renewability of water resources
Residence time of global atmospheric moisture
Volume (storage) of atmospheric water: 13,000km3
Flow rate of moisture from the atmosphere as precipitation= 502,000km3/yr
Tr=13,000/502,000= 0.026yr~9 days
(this is one reason why weather cannot be forecast accurately more than a few days ahead).
What are the following residence times of:
- water vapour over sea
- sea
- rivers
- glaciers and snow
- wetlands
- Groundwater
1 week 100s years 1-3weeks 1000s years (1000-10000) 10s years 1000s years (2 weeks to 10000)
Residence time dictates how renewable water resources are. A water resource that is renewed within a few years could be considered to be renewable and sustainable.
What is the third constraint of water: spatial variability of water?
renewable freshwater resources are not evenly distributed globally
- huge global variation in volume by continent
- global variation in worlds surface water: evaporation and runoff
name some regional aquifer systems?
Northwest sahara aquifer system High plains aquifer California Central Valley aquifer Nubian sandstone aquifer system Indo-Gangetic plain North China plains aquifer Great Artesian basin
how does the quantity of modern groundwater relate to other sources of groundwater?
atmopshere: 12,000km3
vegetation: 1000 km3
Surface water: 100,000km3
Soil water: 16,000km3
Modern groundwater: 347,180km3
How does other groundwater storage compare to modern groundwater storage?
21.97million km3
Potential demand and use definitions:
- gross water demand
- potential return flow
- Net water demand
- potential water requirements to satisfy the needs for agricultural, industrial and domestic sectors
- Potential amount of return flow that would occur from gross demand
- Gross water demand minus potential return flow (or potential consumptive water use).
Actual demand and use definitions:
- water withdrawal
- actual return flow
- cosumptive water use
- actual water amount that is physically withdrawn from available water resources to satisfy gross water demand
- Actual amount of return floww after water is withdrawn from water sources
- Actually consumed or evapotranspired from water withdrawal (water withdrawal minus actual return flow).
define: instream water use
certain uses of water do not impair its availability for further use
define withdrawals
extraction of water from a water body or groundwater resource
define consumptive water use
when water is transformed from a state or location from which ic can be used to one in which it cannot be used . Water used consumptively is not available for subsequent uses.
define non-consumptove water use
Where water is used for a need but is then returned for further use. The water may be impaired and need treatment.
What are the general drivers of demand
tend to be location specific
- population and distribution (urban populations use water in different ways to rural users).
- technology (pipe systems/ drip irrigation/ spray irrigation/ wells).
-economics (driven by world energy production by source/ world cotton prices/ virtual water imports into Europe). - environmental conditions (observed change in annual precipitation over land/ 1901-2011 temperature trend)
+ regional determinants (for example: industry dominant/ industry and agricultural equally dominant/ domestic use widely dominant etc.)
which countries use the largest quantity of water (m3 per person per year)
domestic: australia
industrial: canada
Agriculture: Afghanistan
How much water do we directly consume per country?
Global average is about 100L per day
Uk 150
Germany= 200
USA- 500
4/150 for drinking
50/150 for personal hygiene (showers and baths)
how does the use of water differ between developed and developing countries?
Industrial use of water increases with country income, going from 10% for low and middle income countries to 59% for high-income countries.
world:
domestic use- 8%
industrial use- 22%
Agricultural use- 70%
high-income countries
domestic use: 11%
Industrial use: 59%
Agricultural use: 30%
low-and middle income countries
domestic-8%
Industrial- 10%
Agricultural use-82%
What are the historic changes and implications for the future?
- huge population growth in developing countries
- large increases in agricultural, domestic and industrial uses of water (however, significantly this is based upon extraction of water that has continued to increase quite dramatically in response to growth in consumption).
What did Falkenmark (1980) pioneer?
the concept of WATER STRESS with a threshold
to identify regions of WATER SCARCITY
What is the Falkenmark Water Stress Indicator?
defines per country water stress based
on the per capita annual renewable freshwater resources (~blue water)
The threshold is generally agreed as 1700 m3/year per capita at which water
scarcity occurs with different levels of severity below this.
> 1,700 m3- fine
100-1700m3- regular water stress
500-1000- chronic*
<500- absolute water scarcity
*lack of water begins to hamper economic development and human health and well-being.
what is the water stress situation in the UK
by widely use water stress definitions the UK is currently subject to occassional or local water stress. This is evident from our infrequent experiences of hosepipe bans and pleas for water consevration.
How do you calculate the water stress index?
Falkenmark orginally defined water scarcity on annual, per country water needs but this has evolved since to a spatially explicit and sector specific index that includes agricultural and industrial demand
In general:
WSI= Dtotal/WA
Dtotal= total demand (industry, agriculture, domestic) WA= water availability (generally river flow)
A region is considered to experience water stress when the WSI is higher than 0.4 considering the sustainability of renewable water resources.
The 0.4 threshold correponding to an anual renewable freshwater resources of about 1700m3/yr per capita of the Falkenmark Water Stress indicator
Note: there is a gap between water withdrawl and consumption?
….
Excessive withdrawal of renewable water resources:
Which countries are stressed?
The countries known to be experiencing stress or scarcity of water per capita are
roughly those which are excessively using their renewable water resources
(North Africa, Middle-East and central Asia including Afghanistan and Pakistan).
Define water debt
If the amount of water withdrawn exceeds natural inflow, there is a
water debt
• In such cases, water should be considered as a non-renewable
source that is being mined
Which region is most indebted?
middle east
SAUDI ARABIA (-15km3/year)
Where does high water overuse tend to occur?
High overuse tends to occur
in regions heavily dependent on irrigated agriculture, such as the Indo-Gangetic Plain in south
Asia, the North China Plain and the High Plains of North America, and in areas undergoing rapid
urbanization and industrial development. An estimated 1.4 billion people now live in river basin
areas that are ‘closed’ (in that water use exceeds minimum recharge levels) or near closure
Define: water security
Water security is defined as the capacity of a population to • safeguard sustainable access to adequate quantities of acceptable quality water for sustaining livelihoods, human wellbeing, and socio-economic development, • for ensuring protection against water-borne pollution and water-related disasters, and • for preserving ecosystems • in a climate of peace and political stability.
define: improved water source
piped water into dwelling; public tap/ standpipe; tubewell/borehole; protected dug well; protectd spring; rainwater collection
The global picture shows that the lack of access to clean water remains a burden for the poorest countries, preventing them accelerating their development.
define access to sanitation
Waste water or solid waste treatment infrastructure, well
maintained toilets or linked to a septic tank
For almost all developing countries, access to sanitation remains below the world average. Progress in this matter is particularly important for development, as it is well known that a lack of appropriate sanitation is a factor in the spread of water born diseases - something that could be avoided with minimum investment.
water use and under-development
-In many parts of Asia and Africa hundreds of thousands of people have to walk miles every day to find clean water. The water supply is often limited, it can also run out and is not always safe for drinking. • Lack of appropriate sanitation is a factor in the spread of water born diseases, and early childhood mortality • Populations are vulnerable to water hazards and climate change • Lack of access to clean water remains a burden for the poorest countries, preventing them accelerating their development.
Water implications of development
-If European standards of water consumption were applied to highly populated developing countries, the amount of water needed would have to increase by three to five times. • In the next 30 years the population in these countries is expected to double which means that the amount of water needed would have to increase again.
what is the coming water scarcity in africa?
In a few years from now, almost all sub-Saharan countries will be below the level at which water supply is enough for all. Even worse, most of them will be in a state of water-stress or scarcity.
