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Impacts of Low-Flow Rates on Recreational Rafting Traffic
on the Colorado River in Grand Canyon National Park
Catherine A. Roberts
Joanna A. Bieri
Basic Information
• Bureau of Reclamation, Grand Canyon Monitoring and Research Center(IA # 00-AA-40-4330)
• Cooperative agreement between Grand Canyon National Park & Northern Arizona University (CA#8210-99-002)
Contact Information
• Catherine A. RobertsDept. Mathematics & Computer ScienceHoly Cross CollegeWorcester, MA [email protected]
• Joanna A. BieriDept. Mathematics & StatisticsNorthern Arizona UniversityFlagstaff, AZ [email protected]
Low Summer Steady Flow (LSSF)
• 17,000 - 19,000 cfs in April and May
• Four days of 31,000 cfs in early May
• Steady 8,000 cfs June - September
• Four days of 31,000 cfs in early September
Glen Canyon dam releases during summer 2000
Objective of Study
To examine the impact of LSSF on recreational rafting traffic on the Colorado River within the Grand Canyon National Park.
Outline of the Study
• Collect Trip Reports during LSSF.
• Place information into database.
• Compare “low flow” data to “typical flow” data collected during 1998/1999.
Trip Report
Trip & Flow Classifications
• Commercial = C
• Private = P
• Trip Length = days between Lees Ferry (river mile 0) and Diamond Creek (river mile 225.7).
• Low Flow = LSSF (8,000 cfs)
• Typical Flow = 1998/1999 (19,000 cfs)
Four Trip Types
• Motor– Short 8 or fewer days– Long 9 or more days
• Oar– Short 14 or fewer days– Long 15 or more days
Low Flow Trip Reports
• Short Motor 61 C, 0 P
• Long Motor 3 C, 3 P
• Short Oar 23 C, 2 P
• Long Oar 10 C, 18 P
TOTAL = 120 Trip Reports599 launches 20% return rate
Typical Flow Trip Reports
• Short Motor 222 C, 7 P
• Long Motor 18 C, 9 P
• Short Oar 64 C, 24 P
• Long Oar 18 C, 125 P
TOTAL = 487 Trip Reports1,689 launches 29% return rate
Boat Speed Low vs. Typical Flow
River Speed Normal vs Low Flow
01234567
river mile
normal flowlow flow
Boat Speed: Short Motor
Boat Speed Short Motor(normal vs. low flow)
012345678
river mile
normallow
Boat Speed: Long Motor
Boat Speed Long Motor(normal vs. low flow)
0
1
2
3
4
5
6
river mile
normallow
Boat Speed: Short Oar
Boat Speed Short Oar(normal vs. low flow)
0
1
2
3
4
5
river mile
normallow
Boat Speed: Long Oar
Boat Speed Normal vs Low Flow
01234567
river mile
normal flowlow flow
Average Daily Miles
0
5
10
15
20
25
30
35
40
long oar long motor short oar short motor
normal flowlow flow
Daily Number of Activities
Average Number of Activities
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
all data long oar long motor short oar short motor
average numberactivities normalflow
average numberactivities low flow
Daily Time Spent on Activities
Time Spent on Activities per Day
0:00
1:12
2:24
3:36
4:48
6:00
7:12
8:24
ave time spent per day
normal flowlow flow
Daily Time Spent on Activities
Average Time Spent per Day
0:00
1:12
2:24
3:36
4:48
6:00
7:12
8:24
all data long oar long motor short oar short motor
average timespent normal flow
average timespent low flow
Conclusions
• No change in number of activities/day
• No change in number of miles/day
• Boats spent more time on water
• Boat speeds slower
• 50% reduction in time spent on activities
What’s Next?
• Analysis of campsite and activity visitation frequencies for “low” and “typical” flows.
• Final report to GCMRC
• Several graphs posted on our website:
http://odin.math.nau.edu/~msl