Thaw scallops, if frozen. Cut any large scallops in half. Set aside.
For sauce, in a small bowl stir together water, cornstarch, soy sauce, and sugar. Set aside.
Pour cooking oil into a wok or large skillet. (Add more oil as necessary during cooking.) Preheat over medium-high heat. Stir-fry ginger and garlic in hot oil for 15 seconds. Add celery and carrots; stir-fry for 2 minutes. Add mushrooms and green onions; stir-fry for 1 minute. Sprinkle curry powder over vegetables. Stir-fry for 1 minute more or until vegetables are crisp-tender. Remove vegetables from the wok.
Add scallops to the hot wok. Stir-fry about 2 minutes or until scallops turn opaque. Push scallops from the center of the wok.
Stir sauce. Add sauce to the center of the wok. Cook and stir until thickened and bubbly. Return cooked vegetables to the wok. Gently stir all ingredients together to coat with sauce. Cook and stir for 1 to 2 minutes more or until heated through. Serve immediately with hot cooked rice, chutney, and, if desired, pita wedges. Makes 4 servings.