Mix the white sugar, 1 tablespoon flour and ground cinnamon together, and mix in apples. Pour water evenly over all once in pan.
Combine the oats, flour, brown sugar, baking powder, baking soda and melted butter together. Put half in bottom of pan, pour apple mixture over it, crumble the rest evenly over the apple mixture.
Bake at 350 degrees F (175 degrees C) for about 45 minutes.