U.S. Department of the Interior

U.S. Geological Survey

Bug flow optimizations 

and predictions

Jeff Muehlbauer1

with content and input from 

Ted Kennedy1, Mike Dodrill1, Craig Ellsworth2, and others

1U.S. Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research Center

2Western Area Power Administration FY15-17 Project 5

FY18-20 Project F
Why Bug flows?

 Daily hydropower flows create “tides”

 Insects lay eggs at water line at dusk

 When tide drops, eggs dry, die

Want to 

avoid 

this

Kennedy et al. 2016 

BioScience

2
How do we know?  Water takes time 

moving through 

Canyon

 Some places high 

water at dusk

 Other places low 

water at dusk

Kennedy et al. 2016 

BioScience

3
Goals of Bug flows

 Improve egg-laying conditions for bugs!

 Thus:

 Increase abundance of midges

 Increase abundance/diversity of EPT

 (mayflies, stoneflies, caddisflies)

 Make fish fat and happy Yum

4
What is a Bug flow?

 “Give bugs the weekend off”

 Stable low flows on summer weekends

 Eggs laid on weekends never dry

Unpublished data, subject to change, do not cite.

5
Have we been here before?

 Past steady flows have occurred

 But...

 Summer 2000: Looked for effects during flow

 (no robust monitoring of after-effects)

 2008-2012: Steady low flows Sept/Oct

Unpublished data, subject to change, do not cite.

6
Previous fall steady low flows

 Sept/Oct past peak of bug activity

 Not much egg-laying going on

Unpublished data, subject to change, do not cite. Caddisflies per trap

Midges per trap

5000

0 0

15,000

May Jul Sep Nov May Jul Sep Nov

90% 74%

9% of 

population

8% of 

population

7

2012-2014 Light trap data
Did we see a fall steady response?

 Not really (no surprise)

 Plus, lots of other things going on

 HFEs, Phosphorous, light traps just starting, etc.

Unpublished data, subject to change, do not cite.

8

Blackflies Midges

Mud snails Gammarus

Light traps Drift

2007 2017 2007 2017
What is a Bug flow?

 “Give bugs the weekend off”

 Stable low flows on summer weekends

 Eggs laid on weekends never dry

Unpublished data, subject to change, do not cite.

9
Original Bug flow proposal

 Stable low flows on weekends

 Weekend water level = weekday low level

Unpublished data, subject to change, do not cite.

10
Nuance in a 225-mile-long canyon

 What works at 

Lees Ferry:

 Doesn’t work at 

Diamond Creek:

Unpublished data, subject to change, do not cite.

11
The fix

 Take less water out of weekends

 Can make conditions as ideal as possible:

1. Canyon-wide

2. Or, at certain sites

Unpublished data, subject to change, do not cite.

12
Bug flows optimization

 Take CRFS model from Sed. guys

 218 cross sections throughout Canyon

 Take hydrographs from WAPA

 “Add” 500 cfs, 1000 cfs, etc. to weekends

 Run a bunch of simulations

 Try to minimize:

 ΔStage = weekday low – weekend steady stage

Unpublished data, subject to change, do not cite.

13
Canyon-wide optimization

 Ʃ|ΔStage| 

across all 

cross sections

(Lower = better)

 H = cfs “added” 

to weekend

 ~ H1000 best 

across all 

months

Unpublished data, subject to change, do not cite.

June

H1000

14
Canyon-wide optimization

 Ʃ|ΔStage| 

across all 

cross sections

(Lower = better)

 H = cfs “added” 

to weekend

 ~ H1000 best 

across all 

months

Unpublished data, subject to change, do not cite.

May June

July August

H1500 H1000

H750

H1000

15
 Look at sites of 

particular interest

 Higher “H” needed 

farther downstream

Site-specific optimizations

Unpublished data, subject to change, do not cite.

16
What do we expect?

 Focusing on light trap data

 ~ 1000 samples per year, throughout Canyon

 Robust dataset for tracking response

Unpublished data, subject to change, do not cite.

17

Kennedy et al. 2016 

BioScience
What do we expect?

1. More midges

2. More EPT, more diversity?

Unpublished data, subject to change, do not cite.

18
Predicted response: EPT

Unpublished data, subject to change, do not cite.

 (Mostly caddisflies)

 Abundances 

increase

 Come closer to 

midge counts

19
 Less tied to tributaries

 Again, resemble midges

Predicted response: EPT

Unpublished data, subject to change, do not cite.

Distance from tributary Distance from tributary

20
Predicted response: Midges

Unpublished data, subject to change, do not cite.

 Take existing 

pattern

 Get amount of 

time at dusk, with 

< 5” daily Δstage

 218 sites

 Base flow 

and optimized 

Bug flow scenarios

21
Predicted response: Midges

Unpublished data, subject to change, do not cite.

 Build a shiny, new 

model

 Result: Optimized 

Bug flow improves 

conditions 

 (Just about 

everywhere)

22
Predicted response: Midges

Unpublished data, subject to change, do not cite.

 Improved by how 

much?

 26%, canyon-wide

23
Thanks!

Unpublished data, subject to change, do not cite.

 Bug pickers (for counting the bugs)

 All the bugs (for science)

 Mike Dodrill, Sed guys, and WAPA (for the models and data)

 Y’all (for listening to a 20 minute talk about bug modeling)

June

H1000

24