BOULDER, Colo. -- Boulder city and county officials closed Boulder Creek to all inner-tubing, rafts and belly boats from Barker Dam to the Weld county line, Wednesday afternoon. The closure does not affect whitewater canoes and kayaks.

The Barker Reservoir is full and water is flowing over the dam's spillway, officials said. Spring runoff from the snowstorm in April is also contributing to the swelling of the creek.

According to stream flow readings just east of the Boulder Canyon tunnel, Boulder Creek was flowing at 510 cubic feet per second ; up from just over 100 cfs at the same time yesterday. Predictions call for water flows to reach 800 cfs by Thursday afternoon.

"The creek is extremely dangerous to tubers right now, and it is for safety reasons that we must temporarily close the creek to any tubing until the water is at a safe level," said Mark Beckner, Boulder Police Chief.

"That much water moving that fast is extremely dangerous," said Lt. Phil West of the Boulder County Sheriff's Department. "And it's freezing cold, too. So you have hypothermia to deal with as well."

Wednesday, two people were caught on the wrong side of the creek and had to be rescued because they couldn't get across the torrent.

"If you do choose to kayak or canoe, make sure your name and phone number are on your boat, and if you overturn, please call 911 immediately and let the dispatcher know that you were in the creek, overturned and your boat is still in there but that you are okay," said the city of Boulder Fire Chief Steve Stolz. "We want to prevent putting our rescue staff at risk unnecessarily."

While the creek appears swollen and muddied due to the increasing water volume, and some bike path underpasses are closed, Boulder Creek is not considered to be at flood stage until it reaches 2,000 to 2,500 cfs. The most recent occurrence of such a volume that resulted in the creek being closed was in the spring of 1995.

Signs are being posted along the creek warning tubers of the closure. Violation of the closure order can be enforced by any law enforcement officer and is a petty offense with a $50 fine.

Visitors to Open Space and Mountain Parks trails may also find high water impeding their passage on trails near creeks in the coming weeks. Officials will close trails when necessary for public safety and asks visitors to comply with these temporary closures.

"Public safety is our number one concern," said Steve Taylor, Open Space and Mountain Parks Maintenance Supervisor. "While closures will be kept to a minimum, it is important that visitors do their part by obeying all signs and staying out of areas during these temporary closure periods."