Difference between revisions of "The Bugflow Experiment"

A more diverse and productive aquatic food base could benefit a variety of priority resources, including native fish (including the endangered humpback chub), the rainbow trout fishery, and other riparian species that occur in Glen, Marble, and Grand Canyons. Mayflies (Ephemeroptera), stoneflies (Plecoptera), and caddisflies (Trichoptera), collectively referred to as EPT, are important components of a healthy aquatic food base, but they are notably absent from the Glen and Marble Canyon reaches and very low in abundance and diversity in the Grand Canyon. GCMRC has hypothesized that EPT taxa are recruitment limited, because daily flow fluctuations to meet hydropower demand cause high egg mortality, and the absence of EPT has an adverse effect on the carrying capacity and condition of the trout fishery and native fish communities. EPT are thought to be recruitment limited because Glen Canyon Dam fluctuations create a large varial (intermittently wetted) zone along shorelines. Because the Colorado River in Glen, Marble, and Grand Canyons is canyon-bound and the tributaries that join the river all have comparatively low flow, the size of the varial zone does not appreciably decrease with distance downstream. Thus, although water temperature regimes become more naturalized with distance downstream, the effect that daily flow fluctuations to meet hydropower demand have on the stability of shoreline habitat does not attenuate much with distance from the dam.

This hypothesis attributes the absence of EPT and the poor health of the invertebrate assemblage to the width of the varial zone, similar to earlier investigations (Blinn et al. 1995), but focuses on the effects unstable shorelines have on the eggs of these species. This hypothesis assumes that egg-laying by EPT occurs principally along shorelines. According to the hypothesis, EPT taxa downstream of Glen Canyon Dam are recruitment limited, because daily flow fluctuations to meet hydropower demand negatively affect habitat quality along the shorelines where egg laying is assumed to occur.

To test this hypothesis, macroinvertebrate production flows would be provided every weekend from May through August (34 days total). The flow on weekends would be held steady at the minimum flow for that month, which would ensure that the insect eggs laid during weekends would remain submerged throughout larval development. If the hypothesis is true, there would be an increase in insect production due to the reproductive success of insects that laid eggs during weekends. No change in monthly volumes, ramping rates, or the maximum daily range in flow during weekdays would be required for this experiment. To offset the smaller water releases that would occur during weekends within a given month, larger releases would need to occur during the weekdays within a given month.

Implementation of macroinvertebrate production flows would consider resource condition assessments and resource concerns using the processes described in Sections 2.2.4.3 and 2.2.4.4. These flows may not be tested when there appears to be the potential for unacceptable impacts on the resources listed in Section 2.2.4.3.

Effects of the tests would be evaluated using observation to determine the location where insect eggs are deposited and the emergence rates of species. Depending on the outcome of the tests, the experiment could be discontinued if there were unacceptable effects on other resources. There is also the possibility that implementation would result in confounding interactions with TMF experiments, and this will be discussed during the communication and consultation process as described in Section 2.2.4.4.

Hypothesis: Daily flow fluctuations dry and kill eggs laid in the evening along the shorelines resulting in population level declines in the abundance and diversity of aquatic macroinvertebrates (midges and EPT) below Glen Canyon Dam.
Questions: Do bugflows increase the abundance and diversity of aquatic macroinvertebrates (midges and EPT) below Glen Canyon Dam?

• In areas where evening egg laying is out of sync (Glen Canyon, Upper and Lower Granite Gorge), can we detect increases egg laying and egg survival because of the low weekend flow?
• If observed, does increased egg laying and survival translate into increased larval and adult abundance and diversity?
• Additionally, steady flows are know to reduce aquatic macroinvertebrate drift. Do increases in production and diversity, if observed, compensate for decreases in drift?
  

BioScience Paper

https://www.usbr.gov/uc/rm/amp/twg/mtgs/17jan26/AR19_Kennedy.pdf

• Citizen Science light trap monitoring throughout Glen and Grand Canyons
• Drift: every 2(??) miles in Glen and Grand Canyons
• Artificial egg-laying substrates??
• Weekday vs weekend drift??

• See an increase in the mean midge abundance (number caught/hr) in citizen scientist light trapping where midge abundance has historically been low (Glen Canyon, Upper Granite Gorge, Lower Granite Gorge)
• See an increase in midge egg survival and abundance of eggs laid on artificial substrates during the weekend vs eggs laid during the week in Glen Canyon
• See an increase in EPT abundance and diversity in the mainstem with larvae being caught in mainstem drift
• See an increase in EPT egg laying on artificial substrates in the mainstem

Food Base Page

Oviposition and Egg Desiccation Studies

Foodwebs and Bioenergetics Studies

Measuring Primary Production in the Lees Ferry Reach

Effects of BugFlows and HFEs on the Aquatic Foodbase

• Citizen Science Insect Monitoring

Hyporheic anoxia in the Lees Ferry Reach

Substrate condition and availability for EPT below Glen Canyon Dam

Downstream Recovery of the Foodbase Community in Several Colorado River Tailwaters

Drift and Food Availability Studies

• Invertebrate Drift below Glen Canyon Dam
• Responses of macroinvertebrate drift, benthic assemblages and trout foraging to hydropeaking below Flaming Gorge Dam

• Foodbase: abundance, diversity, availability (drift)
• Hydropower: value, capacity
• Trout and native fisheries: production, condition
• Lees Ferry fishery: access, economics
• Boater safety: Glen Canyon, downstream
• Sediment transport: beaches

• Tributary inflows make mainstem flows anything but "steady" through Grand Canyon
• Changes in nutrients, turbidity, and temperature are also thought to be strong drivers of macroinvertebrate production
• Bugflows may have a compounding affect on production that may not be seen for many bug generations (months to years)

• Kennedy et al. 2016. Flow Management for Hydropower Extirpates Aquatic Insects, Undermining River Food Webs. BioScience
• Deep in the Grand Canyon, Scientists Struggle to Bring Back the Bugs

LTEMP Biological Assessment, pages 30-41

Low steady weekend flows (“Macroinvertebrate Production Flows”) would be conducted to test whether the flows would increase insect abundance. On an experimental basis, for example, flows would be held low and steady for two days per week (weekends) from May through August to attempt to improve the productivity of the aquatic food base, and increase the diversity and abundance of mayflies (Ephemeroptera), stoneflies (Plecoptera), and caddisflies (Trichoptera), which are collectively referred to as EPT.

Modeling Assumptions:

• Macroinvertebrate Production Flows (MPFs) would occur every weekend from May - Aug (34 days, we scheduled July to have the 5th weekend because that how it works out in 2016)
• Weekend flow = minimum flow for the month = weekday minimum flow (see weekly hydrographs on the monthly tabs)
• Hybrid Public Draft monthly volume, ramp rates, or daily change parameters
• Moved weekend water to weekday releases
• Energy prices used in this modeling are for a Saturday, Sunday, and a weekday for May, June, July, and August 2016. These are the energy prices Argonne used in the LTEMP modeling for 2016.

Hybrid Public Draft 8.23 MAF volumes:

• May = 632
• June = 663
• July = 749
• August = 800

Ramp rates: 4,000 up and 2,500 down

Daily change:

• May = 9
• June = 10
• July = 10
• August = 10

Minimum release: 5,000 cfs Maximum release: 25,000 cfs