Turbidity - Revision history

Cellsworth at 20:30, 17 September 2026

2026-09-17T20:30:37Z

Cellsworth at 20:28, 17 September 2026

2026-09-17T20:28:44Z

Cellsworth at 19:48, 17 September 2026

2026-09-17T19:48:34Z

Cellsworth at 19:11, 17 September 2026

2026-09-17T19:11:36Z

Cellsworth at 15:59, 4 November 2025

2025-11-04T15:59:40Z

Cellsworth at 17:50, 3 November 2025

2025-11-03T17:50:28Z

Cellsworth at 17:50, 3 November 2025

2025-11-03T17:50:09Z

Cellsworth at 17:43, 3 November 2025

2025-11-03T17:43:46Z

Cellsworth at 17:17, 3 November 2025

2025-11-03T17:17:14Z

Cellsworth at 17:47, 4 September 2024

2024-09-04T17:47:51Z

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 '''2016'''
 *[http://pubs.usgs.gov/fs/2016/3053/fs20163053.pdf Voichick et al. 2016. Water clarity of the Colorado River—Implications for food webs and fish communities: U.S. Geological Survey Fact Sheet 2016–3053]
 '''1995'''

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 ==Conclusions==
 Despite the presence of nonnative predators, Humpback Chub populations in Grand Canyon have expanded during the past 10–15 years, very likely due to favorably warm river temperature. While Smallmouth Bass in Glen or Marble canyons (between Glen Canyon Dam and the Little Colorado River) may pose a downstream dispersal risk (and potentially a threat to Humpback Chub populations), high turbidity conditions downstream of the Little Colorado River reduce the likelihood of persistent local Smallmouth Bass recruitment. These results suggest that Smallmouth Bass invasion risk to Humpback Chub is not uniform across the Colorado River basin and should be evaluated in the context of the different site- specific water quality and flow regime conditions, other known risks to Humpback Chub, and Humpback Chub population size in different parts of the basin.
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-! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">Questions</h2>
+! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;"> Turbidity Augmentation </h2>
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-Randle et al. (2007) estimated the cost of sediment augmentation from the delta of Navajo Creek within Lake Powell to be approximately $150 million. This estimate contribute enough fines to meet a “200 FNU” condition in the main channel of Marble / Eastern Grand Canyons. Recent studies have shown that as little as 25 FNU might allow for a substantial increase in chub survival from both rainbow and brown trout [https://www.usgs.gov/centers/sbsc/science/effects-water-clarity-survival-endangered-humpback-chub?qt-science_center_objects=0#qt-science_center_objects]. What would be cost estimate for doing sediment augmentation to reach this reduced turbidity target?
+Randle et al. (2007) estimated the cost of sediment augmentation from the delta of Navajo Creek within Lake Powell to be approximately $150 million. This estimate contribute enough fines to meet a “200 FNU” condition in the main channel of Marble / Eastern Grand Canyons. Recent studies have shown that as little as 25 FNU might allow for a substantial increase in chub survival from both rainbow and brown trout [https://www.usgs.gov/centers/sbsc/science/effects-water-clarity-survival-endangered-humpback-chub?qt-science_center_objects=0#qt-science_center_objects].
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-! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3bfb1; text-align:left; color:#000; padding:0.2em 0.4em;"> [https://academic.oup.com/tafs/article/154/5/469/8209825 Pine et al. 2025. Assessing the potential for Smallmouth Bass population establishment in Grand Canyon] </h2>
+! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3bfb1; text-align:left; color:#000; padding:0.2em 0.4em;"> [https://www.usgs.gov/centers/sbsc/science/effects-water-clarity-survival-endangered-humpback-chub?qt-science_center_objects=0#qt-science_center_objects Ward et al. 2016. Effects of Water Clarity on Survival of Endangered Humpback Chub]   </h2>
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-−
-The expansion of nonnative Smallmouth Bass Micropterus dolomieu into the Grand Canyon ecosystem downstream of Glen Canyon Dam is widely seen as a potential threat to native fishes, particularly the Humpback Chub Gila cypha, which is listed as threatened under the Endangered Species Act. This concern stems from observations in the Green and upper Colorado rivers, where dam- modified habitats and reservoir introductions have allowed Smallmouth Bass to become established and impact native fish species. Our objective was to compare habitat conditions between a Smallmouth Bass population center in the Green River— where Humpback Chub are rare— and two major Humpback Chub population centers in the Colorado River in Grand Canyon, where Smallmouth Bass invasion is a conservation concern, to help assess invasion risk and inform management actions downstream of Glen Canyon Dam.
-−
-==Methods==
-We developed a conceptual model of Smallmouth Bass recruitment potential emphasizing the roles of temperature, turbidity, and the timing of these conditions, based on literature for Smallmouth Bass and Largemouth Bass Micropterus nigricans. Using U.S. Geological Survey gauge station data, we summarized daily temperature and turbidity patterns near a known Smallmouth Bass population center in the middle Green River (near Jensen, Utah) and compared those with conditions in the Colorado River in Glen Canyon and Grand Canyon downstream from Glen Canyon Dam. We then used our conceptual model of Smallmouth Bass early life history, along with observed turbidity and temperature patterns, to explore how irregular recruitment could affect Smallmouth Bass population dynamics and individual growth potential using an age- structured population model and a bioenergetics model.
-−
-==Results==
-Although warm reservoir releases due to low water storage in Lake Powell has made temperature regimes in Glen and Grand canyons more similar to those of the middle Green River, the Colorado River ecosystem in Grand Canyon has a very different turbidity regime from that of the middle Green River. The Colorado River in Grand Canyon becomes very turbid during late summer and fall, when tributaries experience flash floods during the North American monsoon season. These periods of high turbidity coincide with critical early life stages of Smallmouth Bass, likely limiting foraging efficiency, growth, and overwinter survival. Our population model indicates that rapidly growing and sustained Smallmouth Bass populations require successful recruitment at least once every 2 years, but empirical data suggest that these conditions occur only every 5–7 years in Grand Canyon. This would make long- term establishment of self- sustaining Smallmouth Bass populations in Grand Canyon unlikely or at least highly uncertain.
-−
-==Conclusions==
-Despite the presence of nonnative predators, Humpback Chub populations in Grand Canyon have expanded during the past 10–15 years, very likely due to favorably warm river temperature. While Smallmouth Bass in Glen or Marble canyons (between Glen Canyon Dam and the Little Colorado River) may pose a downstream dispersal risk (and potentially a threat to Humpback Chub populations), high turbidity conditions downstream of the Little Colorado River reduce the likelihood of persistent local Smallmouth Bass recruitment. These results suggest that Smallmouth Bass invasion risk to Humpback Chub is not uniform across the Colorado River basin and should be evaluated in the context of the different site- specific water quality and flow regime conditions, other known risks to Humpback Chub, and Humpback Chub population size in different parts of the basin.
-−
-−
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-! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">[https://www.usgs.gov/centers/sbsc/science/effects-water-clarity-survival-endangered-humpback-chub?qt-science_center_objects=0#qt-science_center_objects Ward et al. 2016. Effects of Water Clarity on Survival of Endangered Humpback Chub] </h2>
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 Abiotic factors like turbidity can have large impacts on biotic interactions and play an important role in structuring animal communities. Our study suggests that rainbow and brown trout are less effective predators on native chub species as turbidity increases, with turbidity as low as 25 FNU reducing predation vulnerability of bonytail to rainbow and brown trout by 36% and 25%, respectively. Our observed decrease in predation vulnerability associated with increases in turbidity is consistent with other published studies conducted in both laboratory and natural environments. This information may be useful in evaluating the ecological implications of turbidity changes caused by Glen Canyon Dam and in evaluating potential management actions aimed at benefitting humpback chub within Grand Canyon. Relatively small changes in turbidity may be sufficient to alter predation dynamics of rainbow trout on humpback chub in the Grand Canyon. Management actions aimed at augmenting sediment below Glen Canyon Dam have been considered, but not implemented because of high cost. Evaluations of low level silt and clay augmentation only, for the purpose of producing turbidity in the 25-50 FNU range, to reduce predation vulnerability of native fishes may warrant further evaluation and field testing.
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-[[File:Turbidity.jpg|center|600px]]
+[[File:Turbidity.jpg|center|800px]]
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-Introduced smallmouth bass, green sunfish, brown trout, and rainbow trout are considered a threat to the endangered humpback chub in the Colorado River in Grand Canyon. These introduced species eat native fish, but impacts are difficult to assess because predation vulnerability depends on the physical conditions under which predation takes place. The timing, duration, and magnitude of turbidity affects the ability of sight-oriented predators like those fish species listed above to find and prey on fish like humpback chub. Turbidity conditions also impact the ability of these nonnative fish to reproduce and establish in reaches of the Colorado River that still experience turbidity events during the summer monsoon season.
+Nonnative predatory fish like smallmouth bass, green sunfish, brown trout, and rainbow trout are considered a threat to the threatened humpback chub and other native fish in Grand Canyon. These introduced species eat native fish, but impacts are difficult to assess because predation vulnerability depends on the physical conditions under which predation takes place. The timing, duration, and magnitude of turbidity affects the ability of sight-oriented predators like those fish species listed above to find and prey on fish like humpback chub. Turbidity conditions also impact the ability of these nonnative fish to reproduce and establish in reaches of the Colorado River that still experience turbidity events during the summer monsoon season.
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-*[https://academic.oup.com/tafs/article/154/5/469/8209825 Pine et al. 2025. Assessing the potential for Smallmouth Bass population establishment in Grand Canyon]
+*[https://academic.oup.com/tafs/article/154/5/469/8209825 Assessing the potential for Smallmouth Bass population establishment in Grand Canyon]
 *[https://www.usgs.gov/centers/sbsc/science/effects-water-clarity-survival-endangered-humpback-chub?qt-science_center_objects=0#qt-science_center_objects Effects of Water Clarity on Survival of Endangered Humpback Chub]

← Older revision		Revision as of 17:50, 3 November 2025
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		+	*[https://academic.oup.com/tafs/article/154/5/469/8209825 Pine et al. 2025. Assessing the potential for Smallmouth Bass population establishment in Grand Canyon]
	*[https://www.usgs.gov/centers/sbsc/science/effects-water-clarity-survival-endangered-humpback-chub?qt-science_center_objects=0#qt-science_center_objects Effects of Water Clarity on Survival of Endangered Humpback Chub]		*[https://www.usgs.gov/centers/sbsc/science/effects-water-clarity-survival-endangered-humpback-chub?qt-science_center_objects=0#qt-science_center_objects Effects of Water Clarity on Survival of Endangered Humpback Chub]

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 *[http://www.gcmrc.gov/discharge_qw_sediment/station/GCDAMP/09380000 Colorado River at Lees Ferry]
 *[http://www.gcmrc.gov/discharge_qw_sediment/station/GCDAMP/09383050 Colorado River near river mile 30]
 *[http://www.gcmrc.gov/discharge_qw_sediment/station/GCDAMP/09383100 Colorado River above Little Colorado River near Desert View, AZ]
 *[https://www.gcmrc.gov/discharge_qw_sediment/station/GCDAMP/09402500 Colorado River near Grand Canyon, AZ]
 *[http://www.gcmrc.gov/discharge_qw_sediment/station/GCDAMP/09404120 Colorado River above National Canyon near Supai, AZ]
 *[http://www.gcmrc.gov/discharge_qw_sediment/station/GCDAMP/09404200 Colorado River above Diamond Creek near Peach Springs, AZ]