Thoroughly wash and dry arugula and place in large salad bowl. Drain mandarin oranges well and place in bowl with arugula. Sprinkle green onions over oranges and add toss lightly to mix.
In a small bowl, combine lemon juice, olive oil and water and whisk until thoroughly blended. Taste and add salt and pepper as needed.
Pour dressing over salad and mix. Sprinkle walnuts over salad and serve immediately. Makes 6 servings. Enjoy!