Turbidity and Temperature Changes Associated with Whitewater Boating Flows 2008-2014
Black Canyon Bear River, Idaho
1 January 2015
Greg Mladenka and Lynn Van Every
Idaho Department of Environmental Quality
444 Hospital Way, #300
Pocatello, ID 83201
Key Words: Turbidity, temperature, water quality, whitewater boating, Black Canyon, Bear River, Grace,
Idaho
SUMMARY
In 2014, Idaho Department of Environmental Quality (DEQ) personnel continued to monitor water
quality by deploying water quality data recording sondes before, during and after whitewater boating
flow (WWBF) releases to record turbidity, temperature, dissolved oxygen, pH, and specific conductivity
at frequent (15 minute or less) intervals. Additionally, temperature was monitored continuously at five
locations on Bear River upstream and downstream of the WWBF reach. Compiled with information
collected previously (2008-2013) these data indicate marked changes in water quality associated with
peak flows during these events; with the intensity and duration of turbidity peaks decreasing during
subsequent events on an annual basis.
METHODS
YSI model 6920 sondes (Yellow Springs Instruments, Yellow Springs, Ohio) were deployed at the Black
Canyon fishing access footbridge (Figure 1) prior to WWBF releases. Sondes were placed in a protective,
open-ended PVC case with approximate 1.5 inch-diameter holes to allow free circulation of ambient
water around the sonde probes. Temperature, specific conductivity, dissolved oxygen, pH, and turbidity
were recorded at a maximum of 15 minute intervals. Turbidity increases and durations were
determined from these data. Physicochemical data also were collected upstream of Grace Dam in the
forebay and at the boater put-in below the flow release point to determine background. Presently,
turbidity data are collected during three WWBF events each year (first, last and one intermediate
event). For comparative purposes turbidity data were evaluated against Idaho’s water quality standard
for turbidity which reads: “Turbidity, below any applicable mixing zone set by the Department, shall not
exceed background turbidity by more than (50) fifty NTU instantaneously or more than twenty-five (25)
NTU for more than ten (10) consecutive days” (IDAPA 58.01.02.250.02.e).
Sondes were calibrated in accordance with manufacturer’s instructions (Yellow Springs Instruments,
Yellow Springs, Ohio) and the Quality Assurance Project Plan for the Portneuf Basin Monitoring Project
(IDEQ November 2009). Data quality was determined by simultaneous comparisons with freshlycalibrated sondes, post deployment calibrations and checks using a NIST-certified thermometer.
Additional water temperature data were recorded hourly (or more frequently) using Onset Computer
Corporation Water Temp Pro v2 data loggers at five locations (see Figure 1) – above Alexander Reservoir
at Bailey Cr. Road, Grace forebay (surface), Highway 34 Bridge (approximately 600 feet downstream of
Grace Dam), Mid-Black Canyon, and downstream of Black Canyon at the Footbridge/Take-out upstream
of the Grace Power Plant. Temperature monitoring devices were checked against a NIST-certified
thermometer in a constant temperature water bath in accordance to DEQ temperature monitoring
standard operating procedures (DEQ 2013). PacifiCorp also monitored temperature at the Grace Dam
low-flow outlet in 2014. Temperature changes due to WWBFs were estimated based on examination of
continuous temperature data recorded at the Footbridge/Take-out.
Bailey Cr Road
Forebay
Grace Forebay and
low level outlet
Hwy 34 Put-In
Mid-Black Canyon
Take-Out
Figure 1. Turbidity and temperature data collection locations.
RESULTS
Forty-four whitewater boating flow releases have been monitored by DEQ and Ecosystems Research
Institute (ERI; Logan, Utah) since 2008 (Figure 2). Background turbidity (measured at the put-in site
below Grace dam during, and at the take out, prior to the arrival of WWBFs) ranged from 1-34 NTU (see
Appendix). Turbidity was measured in the Grace forebay during several events and ranged from 0.4-40
NTU. Turbidity increases over background measurements (termed “peak turbidity” henceforth in this
report) at the take out ranged from 27-1373 NTU (Figure 2). Annually, general patterns included
highest turbidities during the first several events of the year, with peak turbidities declining for the
remainder of that season’s WWBFs. The highest peak turbidity occurred during the inaugural WWBF in
2008, and was determined from a single water sample acquired by Idaho Department of Fish and Game
staff near the onset of the event. Since turbidity monitoring at these events began in 2008, each year’s
initial peak turbidity declined through 2012 (from approximately 1373 to 355 NTU for 2008 and 2012,
respectively). Initial peak turbidity measurements in 2013 and 2014 were 701 and 786 NTU,
respectively. After these initial peaks, subsequent peaks mirrored those recorded in past years.
Seasonally, initial turbidity peaks were greatest, with subsequent events having lower peaks. During
nearly all multiple, successive day events, turbidity peaks decreased each day. For example on 1-3 June
2012, initial maximum turbidity far exceeded subsequent days’ WWBF-induced turbidity increases (132
versus 32 and 34 NTU for days 1, 2 and 3 June 2012, respectively). The only exception was on 14 June
2009 which was greater than the prior day’s exceedance; however it is clear there was sonde fouling
during this event, so the exceedance estimate is likely high for that case.
Exceedance durations (time while turbidity >50 NTU above background) also declined during multipleday WWBF events and generally declined over the course of events each season (Figure 3). The first
day of each year’s initial WWBF event had the longest exceedance duration for that year. Exceedance
durations that ensued were typically 2-5h. Following implementation of adaptive management
application of higher between-event flows (200 cfs), subsequent flow events in weekend releases
typically had exceedance durations < 1h.
Maximum Turbidity Exceedances and Flows for
Whitewater Boater Flows (2008-2014)
1400
1600
Peak Turbidity
Peak Q
1200
1500
1300
800
1200
600
Flow (cfs)
Maximum Turbidity (NTU)
1400
1000
1100
400
1000
900
0
800
4/14/2008
4/20/2008
6/1/2008
7/12/2008
7/13/2008
4/11/2009
4/25/2009
5/31/2009
6/13/2009
6/14/2009
6/20/2009
6/21/2009
4/18/2010
5/23/2010
7/10/2010
7/11/2010
4/9/2011
4/10/2011
4/16/2011
4/17/2011
4/23/2011
4/24/2011
4/28/2012
4/29/2012
5/5/2012
5/6/2012
6/1/2012
6/2/2012
6/3/2012
4/13/2013
4/14/2013
4/26/2013
4/27/2013
4/28/2013
6/1/2013
6/2/2013
4/5/2014
4/6/2014
4/12/2014
4/13/2014
4/25/2014
4/26/2014
4/27/2014
5/10/2014
5/11/2014
200
Figure 2. Maximum flows and turbidities recorded during WWBFs 2008-2014. Flows are shown as blue
circles and maximum turbidities are grouped by year.
Maximum Turbidity Exceedances and Duration for
Whitewater Boater Flows (2008-2014)
1400
duration NA
on 4-14-08
Peak Turbidity (NTU)
Duration > 50 NTU above background
8
1000
6
800
4
600
400
Duration (hours)
Maximum Turbidity (NTU)
1200
duration NA
on 6-14-09
2
200
0
4/14/2008
4/20/2008
6/1/2008
7/12/2008
7/13/2008
4/11/2009
4/25/2009
5/31/2009
6/13/2009
6/14/2009
6/20/2009
6/21/2009
4/18/2010
5/23/2010
7/10/2010
7/11/2010
4/9/2011
4/10/2011
4/16/2011
4/17/2011
4/23/2011
4/24/2011
4/28/2012
4/29/2012
5/5/2012
5/6/2012
6/1/2012
6/2/2012
6/3/2012
4/13/2013
4/14/2013
4/26/2013
4/27/2013
4/28/2013
6/1/2013
6/2/2013
4/5/2014
4/6/2014
4/12/2014
4/13/2014
4/25/2014
4/26/2014
4/27/2014
5/10/2014
5/11/2014
0
Figure 3. Maximum turbidities (bars grouped by years) and duration in hours > 50 NTU (circles) of
exceedances > 50 NTU. Turbidity of 6/14/2009 event is estimated and duration is not available due to
sonde fouling.
Maximum turbidities occurred early during individual WWBFs, usually within 0.5 – 1 h of the release
arriving (and the onset of turbidity increases) at the take out bridge. During 2012 for example, the first
few WWBFs of the season took longer (approximately 0.5 – 1 h) to reach maximum turbidities than
subsequent events (10-15 minutes).
Temperature changes associated with WWBFs were slight, and varied from positive to negative (see
Appendix). The range of temperature change was -1.9 to +2.5 ⁰C. The event resulting in a 2.5 ⁰C
increase was on 12 July 2008 (when water temperatures were generally warm). During ensuing years,
no WWBFs resulted in temperature increases > 1.6 ⁰C, with most changes being measured in tenths of a
degree Celsius. Temperature monitoring in the vicinity of Grace dam indicated forebay surface
temperatures were warmer than concurrent measurements taken beneath Highway 34 bridge (Figure
4). Low-level outlet temperatures were < temperatures concurrently recorded at Highway 34 bridge.
Figure 4. Water temperature at Grace forebay, low-level outlet and Highway 34 bridge.
DISCUSSION
Changes in turbidity associated with WWBFs were observable even without specialized equipment.
Visual changes in water quality were documented in conjunction with turbidity measurements as flows
increased on 1 June 2012 (Figure 5). Photographs were taken upstream and downstream of the fishing
access bridge as flows increased from base flow. Initial turbidity increases were easily distinguished
visually (for example 2.6 to 14 and 14 to 27 NTU). At turbidities > 50 NTU, large changes (±≥50 NTU)
were still obvious to the unaided eye.
Turbidity = 2.6 NTU at 1128h
Turbidity = 14 NTU at 1148h
Turbidity = 27 NTU at 1148h 50s
Turbidity = 47 NTU at 1149h
Turbidity = 84 NTU at 1149h 53s
Turbidity = 107 NTU at 1150h 29s
Turbidity = 126 NTU at 1151h 15s
Turbidity = 142 NTU at 1152h 27s
Figure 5. Photographs of Bear River water at various turbidity levels during the WWBF event of 1 June
2012. In each case the photograph on the left was taken looking upstream, while the photograph on the
right was taken looking downstream from the footbridge at the Black Canyon fishing access bridge.
From 2008-2012, initial annual WWBF turbidity peaks declined (Figure 2). Initial turbidity peaks in 2013
and 2014 were similar to the 2011 peak. This increase in turbidity could be related to those years’
runoff or management differences. Linked events (2 or more days of releases in a row) always resulted
in lower turbidities on subsequent days in all years. Starting in 2012, WWBFs were provided 2 or 3 days
in a row, with higher flows maintained in between those days than in previous years (for a description of
these flows see the Final Agreement for Black Canyon Boater Flows: Extended Study Period and
Adaptive Management, April 18, 2012). Since that change was implemented, subsequent WWBFs
during day to day events only exceeded criteria for short periods (Figure 3). Following the first weekend
of WWBFs, no exceedances occurred on 2nd and 3rd days of multiple day releases. This differs from prior
years when individual WWBFs spaced over the season would each generate turbidity exceedances
(Figure 3). It appears that grouping WWBFs together and maintaining 200 cfs flows between successive
days has mostly eliminated multi-day turbidity exceedances.
Sediment loads varied among events. Since 2008 (an accurate load could not be calculated for 2008 as
the first event was not continuously monitored) loads resulting from WWBFs have decreased and
appear to have stabilized somewhat (Figure 6; yearly loads were normalized by calculating average
tons/day to account for varying numbers of days monitored each year). There was likely a large amount
of accumulated sediment present in the bypass reach that was flushed during the first several years of
WWBFs.
Figure 6. Total suspended sediment loads associated with WWBFs by event and year, 2008-2014.
Temperature changes associated with WWBFs measured at the take out/fishing bridge were minor,
especially after July WWBFs ceased to occur. Temperature for the low level outlet at Grace dam was
recorded only during 2014. During WWBFs that year, temperature differences between the Grace
forebay and the low-level outlet ranged from 0.3 to 1.3 ⁰ C; however, recorded differences during the
entire deployment period ranged from -0.6 to 5.3 ⁰ C. Greater than expected temperature increases
from the low-level outlet to Highway 34 bridge (this occurs over only a few hundred meters of river
channel length) also were observed (Figure 7). Although unrelated to WWBFs, additional investigation
into this situation is warranted.
Figure 7. Temperature at Grace dam’s low level outlet and Highway 34 bridge.
Reference
DEQ, 2013. Protocol for Placement and Retrieval of Temperature Data Loggers in Idaho Streams
Water Quality Monitoring Protocols—Report No. 10, Version 2
Appendix. Summary of data collected during WWBF events (2008-2014).
Date
Measured By:
4/14/2008
4/20/2008
6/1/2008
7/12/2008
7/13/2008
4/11/2009
4/25/2009
5/31/2009
6/13/2009
6/14/2009
6/20/2009
6/21/2009
4/18/2010
5/23/2010
7/10/2010
7/11/2010
4/9/2011
4/10/2011
4/16/2011
4/17/2011
4/23/2011
4/24/2011
4/28/2012
4/29/2012
5/5/2012
5/6/2012
6/1/2012
6/2/2012
6/3/2012
4/13/2013
4/14/2013
4/26/2013
4/27/2013
4/28/2013
6/1/2013
6/2/2013
4/5/2014
4/6/2014
4/12/2014
4/13/2014
4/25/2014
4/26/2014
4/27/2014
5/10/2014
5/11/2014
IDFG
DEQ
ERI
ERI
ERI
ERI
ERI
ERI
ERI
ERI
ERI
DEQ
DEQ
DEQ
DEQ
ERI
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
DEQ
Black
Canyon
Grace
TSS or difference
general
Forebay Put In
highest SSC
from
backgrd
turbidity turbidity turbidity (mg/L)
before
turbidity
(NTU (NTU)
(NTU) based and after
before
max)
on "I" at takeout
event
(NTU)
7.1
7.1
4.2
2.9
12.8
8.3
5.8
0.4
2.1
6.5
1.7
2.2
2.9
2.4
1.7
8.7
6.9
17.6
19.4
17.6
28.2
20.8
8.7
10.8
4.2
6.1
2.9
4.8
4.9
9.3
15.5
11.7
12.5
14.6
1.9
6.9
3.1
10.3
3.6
7.9
9.8
6.2
8.9
1.4
3.7
20
40
22
24
7-12
8-14
12-20
20
17.6
15.1
26
34
10.9
9.3
11.4
20.8
16.9
11.1
13.8
8.1
15
16.6
21
18
28
21
9.6
8.4
10.4
10.9
8.3
14.8
10.4
8
na
na
na
na
na
na
na
na
na
na
na
na
na
13.4
13.2
8
na
na
12.2
na
6.1
5.4
4.7
na
4.9
na
3.6
na
na
1380
178.2
604.6
514.2
101.6
1193.1
819.3
405.7
283.6
363.5
126.3
49.4
865.3
600.4
743.1
207
820.4
95
92.6
68.6
154.8
51.2
363.4
71.3
166.8
43.3
134.4
37.2
39.4
710
96.2
134.4
56.9
41.1
152.8
44.2
789.4
75.4
184.7
39
115.8
37.5
30.3
146.2
33.8
3460
333.1
1157.9
986.8
175.0
2280.8
1567.4
783.1
545.2
690.3
243.8
95.1
1661.3
1153.3
1428.9
385.4
1567.4
153.1
145.0
102.4
247.6
62.8
685.9
120.6
316.8
75.9
257.0
66.6
70.7
1350.7
159.4
240.1
89.7
55.3
294.3
76.1
1515.1
129.5
352.3
64.2
217.5
64.5
55.7
282.6
62.2
1372.9
171.1
600.4
511.3
88.8
1184.8
813.5
405.3
281.5
357
124.6
47.2
862.4
598
741.4
198.3
813.5
77.4
73.2
51
126.6
30.4
354.7
60.5
162.6
37.2
131.5
32.4
34.5
700.7
80.7
122.7
44.4
26.5
150.9
37.3
786.3
65.1
181.1
31.1
110.9
31.3
26.7
144.8
30.1
Duration (hrs)
>50 above
background
Temperature
change
(~C) 1
peak Q
no sonde
2.3
4.5
4.75
1.5
8.25
2.75
4.5
3.5
1.5
2
0
5.7
4.5
5.5
1.25
5.1
1.2
1.3
0.2
1.9
0
4.75
0.1
1.6
0
1.5
0
0
5
1
1.8
0
0
2
0
4.37
0.87
1.4
0
1.5
0
0
1.25
0
NA
-0.1
0.8
2.5
2
-1.4
0.6
0.8
0.3
0.2
0.1
0
-0.6
0.7
1.4
0.75
-1.9
NA
0
-0.2
0
-0.1
0.3
0.3
-0.4
0.2
0.2
0.3
0.1
-0.8
1.4
1
1.01
0.7
1.58
1.14
-0.44
-0.27
-0.15
-0.1
-0.2
1.08
1.28
-0.94
0.57
1344
940
980
1344
1310
923
939
954
869
877
885
869
877
891
1080
959
900
900
900
900
1500
1500
900
900
900
900
900
900
900
900
900
900
900
900
900
900
900
900
900
900
900
900
900
900
900
est.
Sediment
Load above
Ramp
backgrouind
combined
Rate (f/h) past Lower load/day/year
Black Cyn
(tons) see
notes for def.
0.24
0.24
0.24
0.29
0.27
0.23
0.43
0.4
0.49
0.53
0.5
0.52
0.72
0.65
0.92
0.65
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
57.1
141.8
148.8
74.2
249.9
102.8
118.8
94.6
169.7
55.2
29.3
178.6
101.9
175.5
62.5
170.2
31.3
35.6
30.0
86.2
26.6
127.0
29.8
49.5
23.1
45.7
24.0
17.8
209.6
34.0
56.4
30.5
14.2
63.3
23.9
207.0
30.3
51.7
19.9
35.0
18.9
12.1
45.1
17.6
105.5
117.2
129.6
63.3
45.3
61.7
48.6
Temperature difference is estimated from immediately prior to flow minus the maximum (or minimum) temperature prior to the rate of change decreasing to what appears normal
Mean
Median
Max
Min
S.Deviation
7.9
6.9
28.2
0.4
6.0
19.9
20.0
40.0
8.0
10.7
13.7
12.2
34.0
3.6
7.1
294.7
134.4
1380.0
30.3
338.3
287.0
126.6
1372.9
26.5
339.9
2.0
1.5
8.3
0.0
2.1
0.32
0
2.50
-1.90
0.85
963
900
1500
869
162
76
51
250
12
64
82
63
130
45
35