U.S. Department of the Interior U.S. Geological Survey Dammed and Adrift: Patterns of invertebrate drift throughout Colorado River Basin tailwaters Jeff Muehlbauer, Ted Kennedy Grand Canyon Monitoring and Research Center, Southwest Biological Science Center, USGS

What is invertebrate drift? (And why should you care?)  Entrainment of bugs in water column  Critical life stage/behavior  Food for fish Mmm, drifting bugs…

Key components of drift  Related to time of day  Related to discharge (floods/seasonality)  Need benthic source population

But that’s for small, “natural” streams What about drift in a large-river, consistently cold-temperature, fluctuating water-level, no source-population environment?  AKA, a Tailwater

Key components of drift  Related to time of day  Related to flow (floods/seasonality)  Need benthic source population Dam tailwaters ? ? Dam

Drift in tailwaters  Measureable response to dam impacts  Drift still fundamental, even in tailwaters  Does flow manipulation affect downstream recovery?  How do flows alter community dynamics?

 Glen Canyon Dam, Grand Canyon, Arizona  0 EPT taxa. Only 2 insects  Drift related to distance downstream River mile # / m 3 Accumulation with distance from Dam 0 (Dam) (Dam) One “unique” ecosystem Big dam Big river Big canyon Is this normal for tailwaters? How can we tell?

Sampling drift  6 tailwaters in Colorado River Basin X X X X X X X Fontenelle Flaming Gorge Navajo Glen Canyon Hoover Davis Parker

Sampling drift  6 tailwaters in Colorado River Basin  15-mile reaches, sampled every mile

Sampling drift  6 tailwaters in Colorado River Basin  15-mile reaches, sampled every mile  Spring, summer, fall 2015

Sampling drift  6 tailwaters in Colorado River Basin  15-mile reaches, sampled every mile  Spring, summer, fall 2015  Also collected benthics -- Erin Abernethy, P119 (poster session tonight!!)

 Are there seasonal patterns to the data? 59,378 invertebrates later… Yes! But bigger story is dam-to-dam variation

 Is downstream recovery consistent? Dam-to-dam variation Not at all! Local factors hugely important Sediment loading Trib inflow Blackfly abatement

Does context matter?  Dams vary notably in several ways TailwaterLatitudeDischarge (Q)HI Fontenelle Navajo Flaming Gorge Glen Canyon Davis Parker Hoover HI: Hydropeaking index = mean daily CV in Q (Dibble et al EcoApps)

Response metric  Focusing on ratio of insects : non-insects (for now)  Insects:  Egg-laying vulnerable to hydropeaking  Kennedy et al BioScience  Talk Wed. 13:45, S10 :

Latitude  Meh

Discharge  Well, it’s better than latitude

Hydropeaking Index (HI)  Darn good predictor  Matters far more than latitude or Q (classic predictors)

Summary  Season and context affect tailwater drift  Still searching for “unified theory of tailwaters”  Hydropeaking bad for insects  Not such a big deal for non-insects? Season Context Hydropeaking

Thanks to a startlingly large group of really smart, good people  USGS Flyco lab: Adam Copp, Moriah Evans, Anya Metcalfe, Tom Quigley, Eric Kortenhoeven, Ali Ingram, Dallana Garcia-Pena, David Goodenough, Megan Daubert, Dave Foster, Kim Dibble  USU Bug Lab: Scott Miller, Matt Schroer  OSU Lab: Dave Lytle, Erin Abernethy, Richard Van Driesche  …and Colden Baxter Funding from: US Bureau of Reclamation Western Area Power Administration

Related SFS 2016 presentations on hydropeaking in Colorado River Basin tailwaters  Scott Miller: C10, Sun, 14:00  Anya Metcalfe: S22, Mon, 14:00  Moriah Evans: S25, Poster 73  Erin Abernethy: C06, Poster 119  Jesse Fleri: C06, Poster 118  Ted Kennedy: S10, Wed, 13:45 Holy cow, you can still see these!