In a medium saucepan bring water and sugar to a boil. Add cranberries and return to a boil. Reduce heat and boil gently for 10 minutes, stirring occasionally. Then add blueberries, orange zest, and ginger (if you want your sauce to have an extra kick!) and simmer for 5 more minutes, stirring occasionally. Mash cranberries and blueberries as desired. Pour sauce into a bow, cover, and cool completely at room temperature. Refrigerate until serving. Makes 3 cups.