In a 4-quart soup pot over medium heat, heat the oil. Add the onion and garlic and sauté until the onion begins to soften, about 3 minutes. Add the carrot and mushrooms, and sauté 2 to 3 minutes more. Add the water, tamari, tofu, and ginger. Increase the heat to medium high until the mixture begins to simmer. Reduce the heat to low, cover, and simmer for 10 more minutes.