Results of Early Temperature Analyses of 

the Long-Term Experimental and 

Management Plan EIS

Bureau of Reclamation

Glen Canyon Dam

Adaptive Management Program 

Technical Work Group Meeting

January 24, 2013
“If you want to know how to operate 

the dam for humpback chub, look at 

the last ten years.”

- Bill Pine

Some Advice for the LTEMP EIS
Native fish populations have increased since 2000 and humpback chub at 

the LCR have increased about 100%, also increases observed in the 

mainstem at the LCR.

Primary hypothesis for this is that there has been an increase in 

recruitment due to the improvement of conditions for native fish in the 

mainstem Colorado River.

Fisheries researchers in this program encouraged looking back at the last 

10 years to understand what conditions have led to increases in native fish 

to inform the LTEMP EIS.

Previous studies indicate that at least 12 deg C is bare minimum 

necessary for humpback chub hatching and growth, and 20-25 deg C for 

best growth; 16 deg C often cited as target for spawning/good growth.

Argonne is conducting an analysis of historical Colorado River water 

temperature data to understand water temperature requirements that have 

resulted in improvement in native fish populations.

Background
Degree-Days and Days Above Critical Water Temperatures Colorado River at the LCR

Year Deg-Days > 12 C > 13 > 14 > 15 > 16 > 17 > 18

1990 0 0 0 0 0 0 0

1992 3196.0 0 0 0 0 0 0 0

1993 2629.0 1 0 0 0 0 0 0

1994 3637.2 9 0 0 0 0 0 0

1995 3819.0 1 0 0 0 0 0 0

1996 3951.0 40 1 0 0 0 0 0

1997 3727.6 2 0 0 0 0 0 0

1998 3731.4 0 0 0 0 0 0 0

1999 3816.4 5 0 0 0 0 0 0

2000 4049.7 120 78 0 0 0 0 0

2001 3834.1 59 1 0 0 0 0 0

2002 3715.9 6 0 0 0 0 0 0

2003 4188.4 170 107 11 0 0 0 0

2004 4311.7 170 119 57 24 0 0 0

2005 4706.0 202 175 153 121 82 6 0

2006 4208.6 179 85 10 0 0 0 0

2007 4047.8 142 14 0 0 0 0 0

2008 4095.6 168 108 0 0 0 0 0

2009 4089.4 148 21 0 0 0 0 0

2010 3953.4 122 12 0 0 0 0 0

2011 4309.0 182 150 114 30 0 0 0
Prior to 2002

 Only one year with >100 days above 12 deg C, 

2000 (Low Summer Steady Flow)

 < 10 Days above 12 deg C in 8 years

2003 On

 > 140 days above 12 deg C in every year

 > 100 days above 13 deg C in 5 years, but < 100 

days in 4 years and < 25 in 3 years

 2009-2012, a period of big increases in juvenile 

humpback chub in the mainstem, 21, 12, and 150 

days above 13 deg C respectively

Historical Temperatures Colorado 

River at the LCR
Mean Monthly Temperatures Colorado River at LCR

Year May June July August September October

1990 10.5 11.2 10.0

1992 10.4 11.0 10.7 10.6 10.6 10.5

1993 11.4 11.2 11.5 11.1

1994 10.8 11.8 11.2 11.0 10.8 10.0

1995 10.7 10.8 11.5 11.8 11.6 11.4

1996 10.9 11.6 12.1 12.1 11.7 10.9

1997 10.0 10.3 11.1 11.1 11.2 10.7

1998 10.4 11.0 11.3 11.1 11.2 10.7

1999 10.6 11.4 11.7 11.4 11.2 10.8

2000 11.1 13.3 13.5 13.2 12.0 11.1

2001 11.7 12.3 11.9 11.6 11.9 10.5

2002 11.2 11.6 11.5 11.2 11.6 10.5

2003 11.6 12.3 13.2 13.3 13.9 13.2

2004 11.7 12.1 12.9 13.7 15.0 14.3

2005 12.1 13.7 15.8 16.2 16.7 15.9

2006 12.1 12.5 13.2 13.4 13.7 12.7

2007 11.5 11.8 12.4 12.7 12.9 12.1

2008 10.3 11.8 13.0 13.3 13.6 13.2

2009 11.9 12.3 12.8 12.7 12.9 11.7

2010 10.7 12.1 12.3 12.3 12.8 11.9

2011 10.1 11.4 13.5 14.6 15.0 14.7
Lake Powell Elevation
Colorado River Inflow to Lake Powell
What about 2012?
Conclusions

Temperatures in the Colorado River at the LCR have been significantly 

warmer since 2003 than in the previous 13 years of data, and this is 

probably a big reason for the improvement in native fish, humpback chub 

recruitment, and increases in humpback chub in the mainstem.

The most consistent trend is exceeding 12 degrees C in the mainstem at 

the Little Colorado River, and more specifically exceeding 12 degrees C in 

the months of July, August and September when small fish leaving the 

Little Colorado River need conditions that support growth in the mainstem, 

much lower than the literature would suggest is needed. This may be 

a “sweet spot” providing critical conditions for humpback chub without 

providing benefits to warm water non-native fishes.

This information will be considered in the LTEMP EIS process and in future 

consideration of a temperature control device at Glen Canyon Dam.

Hydrologic and temperature modeling will be used to predict how this trend 

may change over the 20-year life of the LTEMP.