A 16 year old girl fell 15 feet from a rock onto another rock striking her head at the South Yuba River. The incident was reported yesterday afternoon at Mothers Beach, about half a mile above Purdon Crossing Bridge. Nevada County Consolidated, North San Juan Fire, a State Parks Ranger and Sierra Nevada Ambulance responded and found the girl had received a moderate open wound to her head and possible two broken wrists.  The girl was extricated from the river by fire service personnel.  Cal Star 3 landed near the bridge on the river and the girl was flown to Sutter Roseville Hospital for treatment.  Her condition is not known at this time.