Despite access to water during the daylong bike trip on Grand County's Porcupine Rim Trail, the girl apparently succumbed to dehydration, police said.

After pedaling about 14 miles with her mother, father and one of her two sisters, the girl became ill. She was less than a mile from the highway when her father left her in the shade of a tree and went for help, said Grand County sheriff's Deputy Zane Lammert. The father flagged down a Utah Highway Patrol trooper on State Route 128.

"We could see them from the parking lot [of the trailhead]. It was maybe only a quarter mile as the crow flies from the road," Lammert said.

But by the time paramedics reached the girl, she had lost consciousness. Efforts to revive her were unsuccessful. She was pronounced dead before the helicopter that would eventually transport her mother, 34, to Moab, could land nearby.

The girl's parents told police their daughter drank about 70 ounces of water during the ride, Lammert said.

The family had been in the area for several days. Monday's ride was their second or third day trip on the trails east of Moab. The family was camping in an RV just a short distance down the road from the trailhead, Lammert said.

"Sounds to me like they did everything right - woke up that morning, had breakfast, then hit the trail," Lammert said.

But what the California family could not have known was that Monday's temperatures would reach triple digits. "They finished their ride in the hottest part of the day on the hottest day of the year so far," Lammert said.

The girl's mother was flown to a hospital in Moab where she was treated for minor dehydration and released, police said.

mwestley@sltrib.com