Heat oven to 375°F. In 1-quart saucepan, heat salsa and water to boiling. Stir in rice. Cover; remove from heat. Let stand 5 minutes.
Stir chicken, cheese and garlic powder into rice mixture. Spoon 1/2 cup chicken-rice mixture onto center of each tortilla. Fold bottom 1/3 of tortilla over filling; fold in sides toward center, leaving top open. Place seam side down in ungreased 9x9-inch (2-quart) glass baking dish.
Cover tightly with foil; bake 20 to 30 minutes or until hot. Garnish with lettuce and tomatoes.