Melt butter in sauce pan over medium heat. Add in the flour and whisk until smooth and a roux forms (2 minutes). Add onions and celery and saute 5 minutes until soft, but not brown. Add water, potatoes, corn kernels, creamed corn, sugar, salt and pepper. Whisk together until smooth. Cover and simmer until potatoes are barely tender, about 30 minutes. Add half and half and simmer uncovered until soup has thickened into a creamy consistency, about 15 minutes. Season with salt and pepper to taste