How can I get rid of lower abdominal fat?

I am a healthy 15 year old girl (180cm, 68kg) who does fast walking/moderately paced running for 1-2 hours, every single day (unless seriously injured). I eat about 8000kj in a day, and I avoid fat and refined carbohydrates. Most of my body is very lean and athletic but below the belly on there is this reserve of fat that will not go away. I have heard this sort of fat storage is a hazard to one's health What can I do?