Learn more about Boulder Expand at: bouldercolorado.gov

After water skiing one lap around the Boulder Reservoir, Topher Downham wiped out -- hard.

"Maybe slow it down a little," he said, yelling from the water. "It's a little chattery out there."

Two volunteers, who both jumped into the water when Downham went down, helped him back into his sit ski. While one volunteer clambered back onto a nearby Jet Ski, another sat behind Downham in the water, keeping him upright until the boat accelerated.

Downham discovered the City of Boulder's EXPAND water skiing program six years ago, and now he's known around the reservoir as a veteran skier -- several of the boat drivers said he's practically a pro now.

The program supports skiers with varying disabilities, including spinal cord injuries, brain injuries, multiple sclerosis, muscular dystrophy, cerebral palsy and amputees. Each skier is fitted for the equipment, which is provided by the program, depending on his or her needs. The program, which runs from June to August each summer, has 15 to 20 skiers who participate each week.

This summer marks the City of Boulder's 30th year hosting an adaptive water-skiing program. After working for several years as an adaptive ski instructor in Winter Park, in 1983 Boulder resident Jim Ziegler decided to buy a boat and equipment and began recruiting adaptive skiers by word of mouth.

Thirty years later, Ziegler watched from the dock on Tuesday morning as skiers zipped by, while volunteers shuffled between boats.

After his wipeout, Downham sat back up for another lap around the reservoir. He squinted into the mid-morning sun and skimmed the water with both arms as the boat approached the dock. Downham, 44, injured his neck in a diving accident almost 20 years ago.

Now, in addition to water skiing, he's an avid downhill mountain biker, sailor and snow skier, and he works as an outreach coordinator for the City of Boulder's Open Space and Mountain Parks department.

"It's so great when it's super hot out and you get in the water," Downham said.

The eight-week water skiing program requires around 30 volunteers at each Tuesday morning session. Because many of the skiers have little or no function in their limbs, the volunteers are key to helping them in and out of the water safely.

The program takes several precautions to ensure the skiers' safety. A Jet Ski follows about two seconds behind as the skier weaves in and out of the boat's wakes. When the skier falls or asks to stop, a volunteer riding on the back of the Jet Ski immediately jumps into the water to hold the skier upright to avoid submersion in the water. A second boat follows a bit farther behind the Jet Ski in case of an emergency.

The process requires constant vigilance from the army of volunteers, and total trust from skiers.

"It's huge," said Katie Kirkham, 51, who's been participating in the water skiing program since the mid-1990s.

Kirkham, who has multiple sclerosis, said she's always "blown away" when she sees how many volunteers donate time, boats, gas and more to make the program possible. Volunteer boat driver Rodger Stewart is also president of EXPAND Beyond Inc., a separate nonprofit organization that helps raise funds for the water-skiing program.

"Being able to do something that able-bodied people can do anytime for someone with a disability is huge," Kirkham said. "I know there are people who just live for this program in the summers."

Volunteer Paul DiMarchi has been helping out with the program for the last seven years. He drives the rescue Jet Ski that follows close behind the skier, and said he keeps coming back to volunteer each summer because of the skiers' positive reactions.

"Some of these people shriek with delight," he said. "If you can do that, it makes it worthwhile. I love to see smiles on these guys' faces."

--Follow Sarah Kuta on Twitter: @SarahKuta.