If you aren't familiar with the initiative, you definitely should check out UNICEF's 2011 Tap Project video. In Short, WWW helps raise money for under-developed countries that don't have access to clean drinking water. It's an initiative that has gotten a lot of support in the last few years—something that I support wholeheartedly, and an initiative that even the top fashion designers are supporting.
Giorgio Armani has said that he would prove 100 liters of drinking water for children every time someone buys one of his two fragrances. I don't think you have any better excuse to treat yourself to a new fragrance than this!
Another way you can participate in World Water Week is by visiting restaurants and donating $1 for a glass of water you would normally drink for free. See here for participating restaurants.
As Mr. Armani says, "Water is such a simple word—but like all simple words it has a profound significance."