Over a three-week stretch beginning in late May, more than two dozen rangers from three parks monitored river rafters passing through Cataract Canyon during a period of very high flow, rescuing nearly 30 of them. The Green and Colorado Rivers meet within the park, amplifying the flow of the latter, particularly as it passes through the constriction of Cataract Canyon, a lengthy stretch of river with 28 rapids. During high water, this canyon is considered one of the most difficult whitewater trips in the Untied States. This year, a near-record snowpack created very high water levels. When the flow rate increases beyond 50,000 cubic feet per second, as happened this spring, the park puts into effect an incident action plan which stages staff in Cataract Canyon to conduct rescue operations as needed. This was the fifth year since 1990 that the flow levels necessitated implementation of this plan. This year, the period of high water began on May 21st and continued for 21 non-consecutive days. During that time, personnel aboard specially-designed jet boats pulled 46 swimmers from the river, recovered three disabled and abandoned boats, and dealt with four emergency medical incidents, three of which required helicopter evacuations. Response time from the base camp is almost instantaneous compared to eight hours or more from park headquarters in Moab. Twenty-eight rangers from Canyonlands, Arches and Glen Canyon participated in the operation.