Combine the water, salt and carrots in a 2.5-quart saucepan; cover and bring to a boil. Reduce the heat and simmer for 8 to 10 minutes, or until the carrots are very soft. Remove from the heat and let cool. In a blender or food processor puree the carrots and cooking liquid. In a large bowl combine the pureed carrots with the orange juice, nutmeg, and broth, blending well. Cover the bowl and refrigerate 2 hours or until well chilled. Serve cold with a garnish of one fresh orange slice and one mint sprig.