In a Dutch oven, cook beef and onion over medium heat until meat is no longer pink; crumble meat; drain. Add the water, ketchup, Worcestershire sauce, paprika, sugar, salt, mustard and garlic powder. Bring to a boil. Reduce heat; simmer, uncovered, for 20 minutes. , In a small bowl, combine flour and cold water until smooth; stir into the meat mixture. Bring to a boil; cook and stir for 2 minutes or until thickened. Serve with noodles or potatoes.