In a saucepan with a tight-fitting lid, soak the wild rice in 3/4 cup of the hot water for 30 minutes. Add the brown rice and the remaining 1/2 cup of water, bring to a boil and simmer, covered, for about 45 minutes, until the rice is tender.
When the rice has cooked for about 30 minutes, dice the apple and toss with the lemon juice in a large bowl. Add the peppers, celery, red onions, raisins, and walnuts and set aside.
Whisk together the orange juice, maple syrup, spices, and oil. Add the rice and the dressing to the bowl and toss well to combine.