Study Plan - Biological Resource Responses to Fall Steady Experimental Flows Feruary 2010

• Description: Study Plan - Biological Resource Responses to Fall Steady Experimental Flows released for Glen Canyon Dam 2009-12
• State: CO
• Date: 2/1/2010
• Title: Study Plan - Biological Resource Responses to Fall Steady Experimental Flows
• Water Supply Pro - Doc Type: Report/Study

a b
25 - _ . - _ - 25
t df =1 I L (it =2
F -value = 87 79 F -value = T60 b
�C 20 p <0.001 "c 20 P = 0.009 b
O O
rn rn
15 15
0 a
T_,
0 10 T - 0 10
O 0 i
_ 3 E s
-0 5 -0 5 j
O - -�: -0
t z
0 - 0
10 15 STABLE LFV HFV
Water Temperature ('C) Flow Treatment
Figure 1. The effect of water temperature (a) and flow treatments (b) on net production.
LFV = Low Fluctuating Velocity and HFV = High Fluctuating Velocity. Different letters
above bars in panel b denote significant differences among treatment levels based on
Tukey's HSD test. Data are preliminary and have not been peer- reviewed.
a b
0.14 - - - 0.14 ......
d1 =1 _ ilf =2
0.12 - F -value = 17.05 = 0.12 - F -value = 2.98
> _ > P =0089 I
CO p =0.001
0 10 - Q. -. - 3.2 -` r 70 0 10 .
N N
0.08 0.08 i e
0 0 0 -06
0.06`'
'O O.04 0.04 -
0.02 002 -
t =
000 - - - ---- 0.00 - -
10 15 STBL LFV HFV
Temperature ( "C) Flow Treatment
Figure 2. The effect of Water Temperature (a) and Flow Treatments (b) on the Individual
Growth Rates of black fly larvae. LFV = Low Fluctuating Velocity and HFV = High
Fluctuating Velocity. Black flies were left in streams for 10 days. Data are preliminary
and have not been peer- reviewed.
Accumulation of algae and invertebrate biomass might be higher during steady flows if rates of
sloughing and downstream export are higher when discharge is fluctuating. However, rainbow trout and
humpback chub have been documented to forage on drifting food items (Valdez and Ryel, 1995;
McKinney and Speas, 2001), so increases in benthic biomass because of a decrease in sloughing may
actually reduce the quantity of drifting food items that are available to these species. Benthic biomass
data are inherently variable (Stevens and others, 1997) and it seems unlikely that 2 months of steady
flows in the fall, a time when primary production is decreasing and steady -flow mediated increases in
nearshore warming are likely minimal (Korman and others, 2006), will lead to a detectable
8