What Water Crisis? Flashcards
What is the net contribution of freshwater from oceans to land each year?
~44,800km3
What are total global freshwater withdrawals each year?
~4850km3
What percentage of our global blue water resources are we currently using?
11%
Why is there a water crisis then?
Global estimates of freshwater resources and withdrawals mask considerable spatial and temporal variations
There is an incompatibility of water supply and demand
How much of its renewable supply does North Africa use?
Over 100%
What will worsen this spatial divide in the future?
Climate change: wet areas will get wetter, dry areas will get drier
What has the 20th century rise in freshwater withdrawals been driven by?
Expansion of land under irrigation: economic development, climate change
Define water scarcity
Shortage in the availability of freshwater relative to demand
What 5 things does water scarcity affect?
- food security
- access to fresh drinking water
- hygiene and public health
- environmental wellbeing
- economic development
What don’t measures to assess water scarcity consider?
Water in storage
What is falkenmarks (1989) measure of water scarcity?
The water crowding index: when the annual per capita availability of renewable freshwater resources drops below 1000 cubic metres per person per year
What is vorosmarty’s (2005) measure of water scarcity?
When the ratio of estimated annual freshwater demand to availability exceeds 0.4
What is the problem with just measuring freshwater availability on the mean annual river runoff?
It assumes changes in water storage are negligible or unimportant. Eg groundwater, soil moisture, basin storage (reservoirs or aquifers)
Why isn’t storage included in these measures?
There is not enough data on storage
How can we move beyond the use of MARR
Use monthly instead of annual river flow = better knowledge on when to draw/replenish reservoirs or when to grow food
Why is it important that water storage is included?
Otherwise we will not have accurate knowledge on where is water scarce or will be most affected by climate change
What is GRACE
The Gravity Recovery and Climate Experiment
Mission launched by NASA to map and measure groundwater
Can show where people are using more groundwater than is sustainable
March 2002
What indicator of water scarcity do Wada and Bierkens (2012) suggest?
The blue water sustainability index (BlWSI)
What is blue water?
The net contribution of water to the land surface from precipitation after deducting evaotranspiration
Why is the BlWSI better?
Alongside consumptive blue water use, it incorporates non-renewable groundwater use and non-sustainable surface water use
Considers degradation of resources as a result of over-abstraction
Assesses the fraction of consumptive blue water use that comes from non-sustainable resources
What happened between 1960 and 2010?
Consumption of water from non-sustainable surface water and groundwater resources increased by 30%
