Does 40 days make an impact?

A while ago Water for Africa Twitter feed came in with a campaign from a charity called blood : water, which is trying to work against the HIV/AIDS epidemic and water scarcity problems in Sub-Saharan Africa.  The 40 Days of Water campaign encourages people to only drink water for 40 days, which I guess was to try to link its campaign with Lent which is soon ending.   After 40 days of only water, the participants are encouraged to donate all the money they save from abstaining from juice, coffee, tea, alcohol, etc, to the charity to support water projects in Ugandan communities.

I'm not going to criticise this campaign, despite having recently expressed my cynicism towards some development projects.  Rather the 40 Days of Water campaign made me think of how people can be everyday activists with regards to water and the environment.  The Water Footprint Network homepage states that a cup of coffee requires 140 litres of water.  (I personally feel this is a little exaggerated, but I also do not know enough about coffee production to back up that statement.)  However the my point is that we can all think about how much water could be saved by making small changes in our lives.  The 40 Days of Water campaign seems to be to encourage that sort of everyday activism and also combine it with a fundraising effort for blood : water. 

This has made me think, what are some choices I can make in order to ease the strain on the environment?  Does changing small things in our lives really make an impact?  With regards to the work of charities, do campaigns like this produce a sustained flow of donations, enough to translate to sustainable projects in local communities?  Does 40 days really make an impact?