• Page names and short cuts
• Setting up redirects
• Changing links on gwp.org and other sites
• Adjusting your DNS and setting up gwp.org to receive the new traffic
• Inform the search engines of the changes
• Update important source websites, like Wikipedia

Neglecting to update obvious links like UN Water, and Wikipedia is just that - neglect so make sure that you don't leave your site abandoned and use your prior research to thoroughly check every site that links to you and ensure that they update their details or that that they are served a meaningful page via the redirects you set up in step 2.