From my four case studies I have used and from various reading around I think my answer would be:
This obviously is not the case everywhere and in some regions climate change may be the overriding influence on water stress but generally the increase in consumption has been the major factor responsible for water stress.
For future global stress however there has been solid investigations into this!
As I discussed last week depending on the scenario and climate model about two -thirds to three -quarters of future tiver basin areas will have increasing water stress up to the 2050s (relative to current conditions).
Carrying on from Alcamo et al , 2007 global water model ( discussed in last blog) it is found that the principle cause of increasing water stress is growing water withdrawals,( for nearly 90% of river basin area) whereas the principle cause over a much smaller area ( about 10%) is decreasing water availability due to climate change. This is a conclusion reached by most big scholars in the world on water such as Vorosmarty el al 2000 and Oki et al,2003 that future water stress up to 2050 will be more affected by changes in water demand than by climate change. However the factor most responsible for this differs between the scholars.
For example Alcamo et al, concluded that the increase in the growth of domestic use stimulate by income growth was the most influential factor- check out map below. This is projected to be taking place most fundamentally in developing regions hence it is believed that water stress will be increasing over most developing regions. 
dominant sector of increasing water withdrawals
Whereas Oki et al (2003) estimated that the impact of economic and technological development on increasing water stress up to 2050 was smaller than the effect of population growth.
So thats that, humans influence is the answer, both now and near future projections on water stress. However will this still be the case in a hundred or thousand of years?? Well just wait for my blog then ....
hello, I am new to your blog and I am finding the discussion really interesting! I'm just wondering could you explain a bit more what water stress is? Sorry if you have talked about it before and i just haven't read that post!
ReplyDeleteno problem at all. ok well water stress is when the demand for water exceeds the available amount during a certain period or when poor quality restricts. these two things often come under the bracket of physical water stress. however there can also be economic water stress, which results form poor management of the available water resources. there are lots of different ways of technical measuring the extent of this water stress but the one which I use and which you would probably find most straight forward is the Falkenmark indicator. If you read my blog on ' how human activities affect water scarcity' you'll find the different measures in a picture. But put simply it orders the different magnitude of the water stress on the amount of water available water per person per year . hope that helps ! please feel free to ask moree
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