8159

• UCREFRP Catalog Number: 8159
• Author: Trammell, M. and T. Chart.
• Title: Aspinall Studies
• USFW Year: 1999.
• USFW - Doc Type: Annual Assessment of Colorado Pikeminnow Larval Production in the Colorado River, Utah 1992-1996 \
• Copyright Material: NO

Relationship of flow and temperature variables to spawning
The average spring peak flow at the USGS Cisco gage, is 1024 m3/s for the period of
record (1914-1996) which encompasses both pre- and post-regulation periods for the Colorado
River. The historic peak (pre-regulation) was 2073 m3/s, and the highest post-regulation peak
(after 1961) was 1968 m3/s, in 1984. Based on the average peak, this study encompassed 21ow
water years; 1992 and 1994 (<50% of avg.), 2 high water years; 1993 and 1995 (>130% of avg.)
and one moderate year, 1996 (80% of avg.). The magnitude of the peak discharge at the two
gaging stations was strongly correlated (rz = 0.998, p = 0.0001), and the hydrographs followed
very similar patterns (Figure 4a-e).
For ease of discussion, flow and temperature data from the Cisco gage will be used for
the remainder of this discussion. Further, the Moab catch data will be emphasized because catch
rates were likely the result of the two spawning sites combined. Other variables such as onset of
spawning and temperatures were not substantially different between the sites. A summary of
flow and temperature data is given in Table 4.
The magnitude of the peak flow (highest daily mean) was correlated to average monthly
flows in May, June, July, and August (Figure 7). The rz values for each month are: May, rz
=0.63; June, rz=0.96; July, rz x.73; Aug, rz = 0.78. Peak flows were also related to the date of
the peak (rz = 0.70). The higher the peak, the later the date, and the longer the flows remained
high. The peak discharge usually occurs near the end of May or the first of June, with the runoff
period of high flows continuing throughout the month of June.
Table 4. Summary of flow and temperature for the Colorado River, USGS gage at Cisco,
1992-1996.
Variable 1992 1993 1994 1995 1996
Peak discharge a
(ms/s) 484 1348 424 1455 813
Avg June flow 232 782 255 1044 508
Avg July flow 128 330 79 810 200
Avg Aug flow 103 155 73 234 88
date of peak May 29 May 29 May 21 June 19 May 20
onset of spawn June 11 June 29 June 5 July 11 June 23
date of 18°C June 1 June 23 May 25 July 17 June 25
DDb to spawn 1684 1806 1600 2210 1868
DDb through July 2864 2478 2966 2582 2730
DDb through August 3546 3250 3742 3242 3479
a: Peak discharge was the highest daily mean discharge.
b: DD =degree day accumulation
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