how does climate change affect freshwater security?

In order for us to understand the problem of water stress it is necessary to understand the distribution of water on the planet. I already discussed this a little in my previous blog, but just a little more detailed recap provided here by the picture:

Now in this blog I will be assessing the ways in which climate change affect this very small amount of consumable freshwater... heavy stuff!

First what is climate change?? I know I might be stating the obvious but better safe than sorry. 

 When talking about the current climate change occurring in our era we tend to be referring to global warming. This global warming which has been spotted to be happening rapidly after 1950  till today has been presumed by scientists who are 90% sure that this been caused by increasing greenhouse gases created by human activities( although some may contest this) (I.P.O.C, 2007).

Now the big point to take away is that climate change affects the distribution of water on the planet!! It is THIS that affects water stress. Lets now go into the major ways it will do this... 
 One of the most pronounced effects of climate change has been melting of masses of ice. When polar ice melts it melts into the sea which goes hand in hand with seal level rise. The implications of this is that the beautiful freshwater is turned into salty water which we can no longer consume, unless that is if we want to use some expensive desalination systems on it, but that is not really a solution for many of us round the world since we aren't all arabs ( the total use of desalinated water in the near East is estimated to be 3.93km3/year with Saudi Arabia, United Arab Emirate and Kuwait use accounting for 77% of the region). 

Rising sea levels caused by this melting of our glaciers also tampers with the freshwater in our groundwater and estuaries by causing salt water intrusion and hence salinisation(Warner and Simons, 2009).
In the case on inland glaciers when they melt they will contribute to freshwater in rivers and lakes, but this will be a short term relief as when these glaciers have been depleted they can no longer be restored!

Another effect of  global warming, is to increase the amount of moisture the atmosphere can hold. For every  0.6 Celsius rise in temperature (1 Fahrenheit) the the water holding capacity of the atmosphere increases by 4%  and there is projected to be a 0.2 Celsius increase per decade for the next two decades(IPPC, 2007). So because the air can hold more water vapour this leads to heavier and more rainfall when the carrying capacity is exceeded or the atmosphere cools. If you need a visualisation for this just look at tropical rainfalls .. they are very dramatic, unlike small showers in England.
This might sound confusing because more rainfall surely must mean more freshwater. However  although yes rainfall means more freshwater,  heavier rainfall also means more rapid movement of the water back to the oceans- hence reducing our ability to store and use it.

In a warmer climate more precipitation will occur as rain rather than snow. This is bad for freshwater security for two reasons. Firstly evaporation which is more dramatic with the increase in temperatures has a larger impact on water rather than snow therefore more drought will be common. Secondly when snow and ice collect on mountains, water is released slowly into the soil  and into groundwater as opposed to when rain falls. Therefore crucial groundwater will not be replenished. This is extremely important as around 50 % of global domestic water supply is from groundwater and humans are quickly using most of the available groundwater storage already( IPCC chapter 3).

However, we must bear in mind that climate change is not going to reduce the amount of precipitation that is falling on our earth, because this will be the same. BUT what it will do is intensify the water cycle.

                                                            intensified water cycle

In other words, the frequency of dramatic weather events will increase. So flooding will become more common in some areas and droughts more severe in others. These effects are already being seen though in a lot of places. However to see examples of this you will just have to wait for my later blogs to come.. woohooo.

One last point people may not actually consider is that climate change will not only affect supply of water but demand too. This is because as the Earths temperatures rise the amount of water required for animals and humans and plants to strive increases, hence putting more pressure on water resources.

Coming up next…. the ways in which human activities affect freshwater security!!!