1Preheat oven to 350 degrees F. Place a rack in the center of the oven. Grease and flour two loaf pans and set aside.
2In a large bowl, whisk together flours, sugars, baking soda, baking powder, salt and spices.
In a medium bowl, carefully whisk together pumpkin puree, oil, honey and water. Add walnuts.
3Add the wet ingredients to the dry ingredients and use a spatula to fold all of the ingredients together. Make sure to scrape the bottom of the bowl well, incorporating all the dry ingredients.
4Divide the dough between the two greased pans and sprinkle with the streusel topping. Bake for 1 hour to 1 hour and 15 minutes, or until a skewer inserted in the center comes out clean. Remove from the oven. Let rest in the pans for 15 minutes, then invert onto a cooling rack.