My Favorite Vegetable Soup

This is my favorite vegetable soup recipe. This soup is titled "Provencal Vegetable Soup" and it comes from The Joy of Cooking. I actually removed some of the ingredients from the recipe to make it quicker. I removed the pistou (French Pesto) which I think is unnecessary. I also removed the pasta in the recipe. The recipe calls for 2 handfuls of broken thin spaguetti which you can add with the zucchini at the end until cooked.
When I make a vegetable soup, I like it to be full of vegetables and very low calorie. This is the kind of soup that you can eat bowl after bowl without feeling heavy. The saffron adds a touch of gold to the recipe.

Provencal Vegetable Soup or Soupe Au Pistou(Adapted from The Joy of Cooking)
Ingredients:

2 tablespoons of oil
1 medium onion, chopped
1 carrot chopped
1 leek, chopped
1 large rib celery, chopped

2 medium ripe tomatoes, chopped
1 small potato, peeled and chopped
8 cups of water
2 teaspoons of salt
Pinch of saffron

1 small zucchini (peeled and chopped)

1. Heat the oil
2. Add the first group of ingredients and cook until tender, not browned(5 to 10 minutes)
3. Stir in the second group of ingredients.
4. Bring to a boil and reduce the heat. Simmer until the potatoes are tender, about 30 minutes.
5. Stir in small zucchini. Simmer a little longer.