Melt margarine in a large Dutch oven over medium-high heat. Add carrot, parsnip, and celery; sauté 3 minutes. Stir in flour. Gradually add broth, water, salt, and pepper, stirring with a whisk; bring to a boil. Cover, reduce heat, and simmer 5 minutes. Add noodles and chicken, and bring to a boil. Cover, reduce heat, and simmer 10 minutes. Stir in parsley.