U.S. Department of the Interior

U.S. Geological Survey

Assessment of tEstimated EffecExperimental OpResources BeloCanyon DamTechnical Work GrouNovember 8 and 9, 20
Overview

 Background and Option Descript Assessment Results (Melis) Economic Assessment Results (P Evaluation of Experimental Desig Scientific Recommendations (Ha Peer Review Process (Garrett)
Part I

Background and Option De
Background

 1996 Record of Decision Goal: “permit 

long-term sustainability of downstream while limiting hydropower capacity and only to the extent necessary to achieve long-term sustainability”

 SCORE evaluated resource responses  SPG established to develop effective lo

direction for future experimental reseamanagement activities

 Three experimental options identified t

process

 A fourth option was added by TWG in O
Purpose of the Assessment 

 Provide information about how ea

proposed experimental options is 

(a) affect downstream biological

and sociocultural resources; 

(b) influence hydropower resour

associated economic benefits; 

(c) contribute to the understandi

relationships between actions resource conditions. 
General Methods

 2005 knowledge assessment fina

 Peer-reviewed literature Expert opinion

 New models

 Daily stage variation Downstream temperature (mainstem)

 Hydropower economic analysis ( Independent peer review
Experimental Options
Experimental Options (cont
Part II

Assessment Result

“Resource Responses fo

Non-Flow Treatment
Flow - Water Temperature (

1. Main channel – Differences betw

options typically small (< 0.5 °C) model uncertainty

2. Nearshore – Steady flows enhan

nearshore warming. Option B rafollowed by Option C. Options A Variation are not expected to difBASE.
Flow - Diurnal Stage Variati

1. DSV is the difference in stage betwee

high flow and daily low flow

2. Option B: reduced DSV in all months, 

steady flows, ~1.5 ft during constrain

3. Option C: reduced DSV in Sep-Oct ste

ft); increased DSV (~2 ft) during wintefluctuations

4. Options A and A Variation: Similar in 

Option C, also increased DSV (~1 ft) dincreased fluctuations
Flow – Fine Sediment

Experimental options ranked in order 

fine sediment retention 

1. Option B - BHBFs increase sandbar size, s

least under stable flows 

2. Option C - BHBFs increase sandbar size, fa

limit sand export, relaxed constraints on fluoffset effects of stable flows on sand retent

3. Option A - BHBFs increase sandbar size, r

constraints on fluctuations may offset effecsandbar size

4. Option A Variation - BHBFs increase sandb

relaxed constraints on fluctuations likely ofBHBFs on sandbar size
Non-flow - Water Temperature 

 All options 

significantly warmer than BASE during spring, summer, and fall. Differences among options (other than BASE) typically small and within model uncertainty. 6

8

10121416182022

Oct Nov Dec Jan F

Average mainstem water

temperature over last 5 years ( o

C)

BaseOption AOption A varOption BOption C
Biological Resources

1. Current Glen Canyon Dam release tem

below optimum for most aquatic orgaincluding rainbow trout

2. Aquatic organisms (algae, invertebrat

to increase growth with warmer water

3. TCD operation and/or natural warmin

necessary for aquatic organisms to eresponse to warmer temperatures

4. All four options result in similar temp
Aquatic Habitat Stability

1. High DSV, especially Mar-Oct, li

productivity of algae and aquatbecause of habitat destabilizatio(desiccation, freezing)

2. Limiting DSV increases permane

habitat, increasing area for primproductivity and invertebrate pr
Aquatic Habitat Stability

1. Young humpback chub use sha

nearshore habitats in Little Colo

2. High DSV reduces available nea

habitat for fish in the Colorado R

3. High DSV reduces potential for n

warming, reducing fish habitat sthe Colorado River
Aquatic Habitat Stability

1. Option A: Greater DSV reduces habitat stabil

warming

2. Option A Variation: Greatest DSV and increas

rates, so least stable habitats among four oppotential for nearshore warming

3. Option B: Least DSV, so creates most stable 

warmest nearshore habitats in most months

4. Option C: Habitat instability Dec-Feb with inc

and Oct habitat stability and warming (may hflows in future)
Flow – Cultural Resources

Experimental options ranked in 

likelihood of fine sediment rete

1. Option B - BHBFs increase sandba

sandbar erosion under stable flows; benefit archaeological sites

2. Option C - BHBFs increase sandba

stable flows limit sand export; relaxon fluctuations may offset effects of and limit the amount of dry sand avaredistribution to higher elevations
Flow – Cultural Resources (

3. Option A - BHBFs increase sandba

relaxed constraints on fluctuations effects of BHBFs and keep more saninundated/wetted, preventing redist

4. Option A Variation - BHBFs increas

size, most relaxed constraints on flukeeps more sand inundated/wetted time, preventing redistribution
Flow – Recreation

Flows have multidimensional 

recreation. Effects to anglers deffects to whitewater boaters, preferences of both user grouconsiderable overlap. Effects tphysical and biological resourcampable area, rapids and wattemperature, etc.) are considewith social science surveys daangler/boater flow preferences
Flow – Recreation

1. Option B: – appears to offer most benefic

terms of retaining campable area, maintai

are preferred by most anglers and boaterssafety, and preserving overall recreation e

2. Options C, A and A Variation: - offer incre

optimal recreational conditions for both aboaters overall

3. Option A and A Variation: – potentially mo

terms of reducing pathogen concentrationsites
Non-flow – Recreation

1. With TCD, all options significantly wa

BASE during spring, summer, and fatemperatures improve safety and enjrecreationists but may also increase loads.

2. Trout removal has localized negative 

anglers and possible minimal impact (impacts to wilderness-like experienc

3. HBC translocation may restrict anglin

opportunities in tributaries and impaexperience of backcountry users
Non-flow – Cultural Resour

1. Trout removal has been identifie

American tribes as having a potnegative impact on traditional cplaces

2. Depending on location, transloc

impact archaeological sites and cultural places because of the aresearch and monitoring activit
Part III - Economic Assessmen

Western Area Power Administration - provided an evaluation on the ec

four experimental options. The evaluation concluded that the economissue of hydraulic head that Option A Variation is consistently above Oincreased economic value. Both Option A Variation and Option A conseconomic benefits than those provided by BASE operations in terms o

production. Option C vacillates between positive and negative econom

year evaluation period. If an August stable-flow trigger is applied to Opimpact of the option is strongly tied to hydrology and hydraulic head w

operations. Option B reduces economic benefit significantly comparemost years. However, Option B returns to modified low fluctuating flow2014–16. For example, under the most-probable hydrological conditio

economic impact of the four options compared to BASE operations, ba

average, ranges from a $7.5 million increase in the economic value und

a decrease of $28 million under Option B (2006 dollars).

BHBFs - Each of the four options under consideration includes the tes

of a BHBF varies by option, hydrological condition, and time of the yeaplace. Example - if a BHBF was conducted in the fall of a year with the 

hydrological conditions, the cost of the BHBF would range from approOptions A and B to $4.3 million for Option C when compared to BASE 
Part IV

Evaluation of Experimental 
Options A and AV

Experimental DesignApproach: Reverse Titration StrengthsTests implementation of a suite of action

resource responses, including:

 Wider flow fluctuations and steep

rates 

 Minimum flows to protect food ba Implementation of a TCD  Nonnative fish management  Translocation of humpback chub 

tributaries
Options A and AV

Experimental Design (cont.)Weaknesses Presumes that the actions needed to 

GCDAMP goals are known

 Simultaneously implementing multip

confound the assessment 

 Implementing a new flow regime and 

will confound the assessment of the experiment

 The option provides for no testing of 

to protect/restore downstream resou

 There is no basis in the literature for 

titration concept 
Option B

Experimental DesignApproach: FactorialStrengths Incrementally tests the effects of pro

longer periods of stable flows and intemperatures in combination with othon target resources

 Provides for testing under two hydro

scenarios over period of 14 years

 Test of the effects of steady flows (ha

on target resources by implementing longer periods of stable flows
Option B

Experimental Design (cont.)Weaknesses Natural factors may confound results Implementing a new flow regime at th

confound the ongoing experiment 

 Does not include testing of the effect

fluctuating flows 

 Length (2 years) and timing of steady 

increments may not be sufficient to eeffectiveness on target resources 

 Specification of how nonnative fish c

implementation of a TCD will be factoexperimental design is not provided
Option C

Experimental Design

Approach: Forward TitrationStrengthsTests implementation of a series of treatments to imp

the relationships among treatments and the resouthose actions, including:

 September/October steady flows and possible  Wider fluctuations Dec. to Feb. to benefit hydr Relaxed ramping rates in 9 months to benefit h BHBFs to conserve sand resources Implementation of a TCD  Nonnative fish management

 Includes a formal 5 year review  Limits treatments that may confound the results o
Option C

Experimental Design (cont.)

Weaknesses Natural factors may confound re Implementing a new flow regime 

will confound the ongoing exper

 Specific details on implementati

treatments using the forward titrare not provided
Part V - Scientific Recomme

 Complete the current experiment (MLFF) Specify desired future conditions Implement and scientifically test a tempera

device 

 Continue testing sand-enriched BHBFs Hydrologic variability masks the effects of 

Dam operations in wet years 

 Limit confounding variables Conduct stable flow tests after current exp

completed, as needed

 Continue model development to support m

decisions
Part VI 

Peer-Review Process