Proposed Modifications for 

Glen Canyon Slough 

Adaptive Management Work Group Meeting, August 16, 2023 

Kerri Pedersen, Bureau of Reclamation, Adaptive Management Group 
Upper and Lower Slough (-12 mile slough) 

Lower Slough Upper Slough 
 

Comparison of Summer Discharge and Water 

Temperature for 1987 & 2023 

July & August 1987 

Discharge (ft3 /s) 

30,000 

25,000 

20,000 

15,000 

10,000 

5,000 

0 

7/1/1987 

Discharge River Temp 

7/15/1987 7/29/1987 8/12/1987 8/26/1987 

24 

21 

18 

15 

12 

9 

Temperature (o C) 

6 

July & August 2022 

30,000 

25,000 

20,000 

15,000 

10,000 

5,000 

0 

7/1/2022 

Discharge (ft3 /s) 

Discharge River Temp 

7/15/2022 7/29/2022 8/12/2022 8/26/2022 

24 

21 

18 

15 

12 

9 

6 

Temperature (o C) 
Lower Slough Temperature Compared to Colorado River -

Summer 2022 

5 

10 

15 

20 

25 

30 

35 

6,000 

10,000 

14,000 

18,000 

22,000 

26,000 

30,000 

7/30/2022 8/6/2022 8/13/2022 8/20/2022 8/27/2022 

Temperature (o C) 

Discharge (ft3 /s) 

Discharge 

River Water Temperature 

Lower Slough Water Temperature 
Proposed Slough Modifications 

Phase 1 

Excavation 

Phase 2 

Excavation 

Phase 3 

Channel Fill 

Upper Slough 
Phase 1: Partially Drain the Upper Slough 

• Excavate a 2-ft wide channel 

(160 ft long) with manual 

labor using picks, shovels, and

pry bars 

• Excavate to a depth of 0.1-2.5

ft which results in 65 yd3 
 

Phase 1: Partially Drain Slough 

Reduce acreage from 0.3 to 0.1 acres 
Phase 2: Excavate Side Channel to Connect 

Sloughs to River 

 Excavate a lower side channel 730 ft long with small excavator 

 Place 1300 yd3 of excavated material (sand, gravel, cobble) in 

Upper Slough 
Phase 2: Connect Sloughs to Colorado River at 8,000 cfs 

10 cfs 
Phase 3: Narrow Width of Lower Slough 

 Narrow slough to width of 80 ft 

 Place sand, gravel, and cobble 

along right bank of slough using 

small mechanized equipment 

 Fill volume of 8500 yd3 with 

depths of 2-3 ft 
Proposed Excavation and Fill Areas for Phase 3 
 

 

Implementation Requirements 

Phase Activity Crew 

Size 

Duration 

(days) Cost 

1 Use hand tools to connect Upper and Lower Sloughs 6 5 $ 

Plant floodplain vegetation (optional) 6 2 $ 

Mobilize small mechanical equipment 4 $$ 

2 Excavate channel to connect Upper Slough to Colorado River 4 7 $$ 

Plant floodplain vegetation (optional) 6 5 $$ 

Narrow Lower Slough with excavated material 4 30 $$ 

3 Plant floodplain vegetation (optional) 6 15 $$ 

Demobilize equipment 4 $$ 
Summary 

 This project could be implemented in phases or all at once. 

 The purpose is to modify the habitat to allow water 

temperatures in the sloughs to approximate the river and 

increase velocity in the slough. 

 Modifying the habitat is more sustainable than removing nonnative fish annually. 

 Habitat modifications are expected to be self-sustaining and 

require little, if any maintenance. 
 

 

Questions? 

https://www.usbr.gov/uc/progact/amp/amwg/2023-08-17-amwgmeeting/20230817-GlenCanyonSloughProposedModifications-508-

UCRO.pdf 

Thanks to Mike Sixta & Tim 

Randle from Reclamation’s 

Technical Services Center 

for evaluating the sloughs!