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 01610croberts@mathcs.holycross.edu

• Joanna A. BieriDept. Mathematics & StatisticsNorthern Arizona UniversityFlagstaff, AZ 86011-5717jab34@dana.ucc.nau.edu

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