An Outline and Schedule for the Development of a Science Plan for WY 2000 

Steady Flows 

Prepared by Barbara Ralston and Mike Yard 

Introduction

An element of Fish and Wildlife’s Biological Opinion for humpback chub (Gila

cypha) includes evaluating the utility of steady flows for native fish recruitment and 

survivorship. Testing flows of this type was also included in the Environmental Impact 

Statement for Glen Canyon Dam. Tests of these flows are to occur in low water years 

(8.23 maf). In a effort to respond to elements of the Biological Opinion, the Bureau of 

Reclamation has proposed instituting steady flows in WY 2000, even though water 

delivery is projected to be more than 8.23 maf. 

A design of flows for native fish is in draft form (Valdez et al, in prep). The 

flows include steady flow elements as well as spring and fall spikes of magnitude 31,000 

cfs (Fig 1). The spikes are anticipated to last 4 days. The experimental hydrograph 

crosses over water years, running from March to March the following year. For 

comparison, the design recommends following a similar hydrograph in another year, but 

under fluctuating flows. Consecutive years are not required to run each hydrograph, but 

water allocations between 2 years require some forethought. Otherwise, the spring and 

late fall component may be compromised. The draft report (Valdez et al, in prep) should 

become final in March 2000. 

 As a means of exploring the idea of testing steady flows this summer, the Bureau 

of Reclamation and Grand Canyon Monitoring and Research Center (GCMRC), 

convened meetings of researchers and stakeholders. The meetings were held in Flagstaff, 

and Marble Canyon, Arizona on February 9 and 16. The purpose of the meetings were to 

1) review current basin hydrology; 2) introduce the experimental hydrograph (Valdez et 

al, in prep); 3) discuss the assumptions (see below) and hypotheses associated with steady 

flows and native fish; 4) elicit comment on the experimental hydrograph; and 5) to 

determine how the hydrograph might be shifted as the upper basin hydrology and inflow 

into Lake Powell change through the water year. Following the meeting on the 16th, 
researchers were asked to rank hypotheses as to their importance, and if they were likely 

to provide further understanding of the system (i.e., testability). 

Responses from researchers and stakeholders included the requested rank, reasons 

why the flows should not be done at this time and data collection should not considered, 

and questions about the potential negative effect elements of the flow might have on 

other resources. The reasons for not conducting these flows and collecting data around 

them include: 

1. Insufficient preparation time to develop a well planned experiment. 

2. Insufficient baseline data (including insufficient understanding of the natural 

history and life history of native fish species). 

3. Lack of consideration for controls (temporal or spatial). 

4. Hydrograph that contains too many treatments and would confound results. 

5. The spring portion of the hydrograph financially impacts the trout fishery. 

6. The SWCA hydrograph suggests testing a fluctuating flow hydrograph first. 

7. Fall spikes may effect the Lees Ferry trout fishery and food base. 

Reasons for conducting these flows and collecting data around them include: 

1. Information about patterns found in association with these flows (longitudinal, 

local scale) can serve to develop more refined hypotheses (the processes or 

mechanisms that underlie the patterns) to be tested in subsequent low flow 

years. 

2. The current hydrology provides an opportunity to evaluate key assumptions 

about steady flows. 

3. Similar data would need to be collected if it were steady or fluctuating under 

the ROD given the low hydrology predicted for WY2000. 

4. Do it if you can learn something from it. 

5. Data from 91-97 could be used in some cases for “baseline”. 

Developing a Science Plan 

Evaluating the effects of experimental flows for native fish encompasses variables 

associated with physical habitat, individual species life history traits, interactions between 

these species and the habitat, and interactions among species. Determining the causeeffect relationships of a treatment in a natural and regulated system is a complex task. 

The benefit of a regulated system is that flow can be planned to some extent. However, 

the task is complicated in a regulated system when flows that are planned become 

interrupted by natural climatic conditions that require changes in magnitude and duration 

of discharge. 
The choice of what data to collect is influenced by the level of certainty that the 

effort will be useful. While there are recommended discharges associated with steady 

flows (Valdez et al, in prep), reservoir levels, and basin hydrology require responsiveness 

to spill avoidance issues. Hence, the recommended experimental hydrograph may be 

shifted in areas of duration (e.g., longer high spring discharge) and discharge volumes 

(e.g., higher than 8k cfs summer dishcarge) to respond to these hydrologic variables. In 

light of the uncertainty around climatic forecasts and reservoir inflows, the science plan 

GCMRC is providing focuses on steady flow questions and not necessarily questions that 

are specific to 8,000 cfs steady flow discharges. We do not anticipate collecting data that 

can make direct cause-effect relationships (mechanisms) given the short amount of 

planning time available and the uncertainty of the hydrology. With this in mind, the 

GCMRC has focused on those efforts that will provide 1) system-wide information on 

physical and biological parameters (sediment budget, temperature, habitat availability, 

distribution and fish distribution), and 2) local scale information on individual resources 

that are either the target of these flows or that may be impacted by these flows (native 

fish distribution/relative frequency, trout, aquatic food base, riparian vegetation). 

Process for prioritizing areas of focus 

Planning for data collection and experimentation around operations of Glen 

Canyon Dam is dictated by a hydrologic forecast that provides researchers and planners 

short notice, roughly one month, of what will be released from the dam. Releases can be 

planned, but up to a month in advance, the releases are still predicted, not assured. Data 

collection planning can take place prior to a month, but the implementation and 

budgeting for any data collecting efforts will still be driven by hydrology and the month 

by month releases. Experimental hydrographs are less compromised by climatic 

uncertainty when reservoir levels are low. 

The uncertain hydrology requires a science plan that can be flexible in its 

approach. As the hydrograph changes, some projects that may be initiated, may have to 

be concluded early or abandoned, other efforts may still provide information about steady 

flow dynamics (e.g., single value measurements like channel velocities at stage x). The 

latter example helps discern patterns of response to the treatment, and is a step in learning 

about the mechanisms underlying the observed response. The mechanisms are the 
interactions between variables that ultimately provide information about the effects of 

flows on resources and subsequently influence management decisions. 

Biological resources were not the primary focus of study under research flows 

conducted in 1990. True, there were periods within this time frame that included steady 

flows, but the time period around these events were not sufficient to determine effects on 

biological resources. In contrast, a prolonged period of steady flows is an opportunity to 

learn about physical parameters in a habitat context, and to compare patterns known to 

occur under fluctuating flows to patterns that might occur under steady flows. This is not 

to say that observations made during one set of steady flows provide definitive 

information about steady flows and biologic resources. The biological program at 

GCMRC has taken into consideration the need for a flexible study plan, and has used the 

rankings of hypotheses by researchers to provide a focus for data collection efforts. We 

have also incorporated comments/questions about the hydrograph to recommend studies 

that may help resolve these questions and refine the experimental hydrograph. In a sense, 

the later elements represent a review process of the experimental hydrograph. We have 

developed system wide questions around patterns that can be viewed relative to historic 

data, and developed local scale questions around variables we can confidently measure 

and the response determined to be associated with steady flows. 

Hypotheses were built around the following eight assumptions about steady flows 

and the native fish community. Some of the assumptions address physical habitat 

variables, while others address biological resources (fish, aquatic foodbase, vegetation). 

Some of these assumptions are not immediately testable or verifiable. 

Assumptions Underlying Endangered Fish Research Flows

1. Steady flows (i.e., 8,000 cfs) will provide consistently available low-velocity near 

shoreline habitats. 

2. Water temperature will increase during summer steady flows both longitudinally and 

in and along near shoreline habitats, and 8,000 cfs flow provide greater warming than 

higher discharges. 

3. Productivity (primary and secondary) is enhanced by steady flows and food 

availability is sufficient to compensate for the increased energetic demands of 

younger faster growing fish. 
4. Steady flows stabilize habitats used and will benefit young fish survivorship. 

5. Hydrology that simulates the seasonal patterns of the natural hydrograph benefits 

native fish more than non-native fish. 

6. Predator-prey and competitive interactions between non-native and native fish will 

not offset the positive effects on native fish derived from the increased availability of 

suitable habitat for rearing. 

7. Impounding tributary mouths, primarily the LCR, retains larvae and immediate postlarvae allowing them sufficient growth to survive when they enter the mainstem in 

the summer and find increased suitable habitat. 

8. A spike flow of 33,000 cfs for 4 days in spring will create suitable habitat and 

displace non-native fish, and a spike flow of 33,000 cfs for 4 days in fall will 

disadvantage non-native fish relative to native fish. 

These assumptions were stepped down to hypotheses that we categorized into 1) Physical 

habitat, 2) Biotic habitat, 3) Aquatic foodbase 4) Fish response. These are the hypotheses 

that we recommend focussing data collection efforts around. In some cases, monitoring 

should cover these hypotheses, other cases will require data collection efforts specifically 

tied to these hypotheses. 

1. Hypotheses addressing physical habitat parameters 

Ho: Current velocities for near shoreline habitats (e.g., talus, debri fans, 

vegetated shoreline) will not differ significantly between fluctuating and 

low steady flow conditions. 

 

Low velocity habitats are assumed to be a requirement of young fish. 

Decreased velocities presumably accompany lower discharges. The lower 

velocity environments may be reflected in an elongation of a particular 

low velocity environment or an increase in the number of these 

environments. 

 

 Ho: Current velocities will increase in tributary confluence areas under higher 

mainstem flows. 

 

Valdez et al. (2000) recommends a high spring steady flow to pond 

tributaries and retain young of the year, assuming that velocities will be 

reduced in tributary confluences. This hypothesis could be tested with 

flows at 17,500 cfs or higher and if flows are reduced to 14-12 cfs for a 

sustained period of time. 
Ho: Areal extent of low velocities does not vary for a range of steady flows. 

 

Discharge may affect current patterns (eddies may get wider or longer), 

but total area of low velocity environments should remain the same. This 

helps determine if size of low velocity environment matters.

 Ho: Water temperatures in the mainstem will not increase downstream greater 

than temperatures previously observed under other flow conditions (e.g., 

fluctuating, higher discharge). 

We have an estimate for rate of warming in the mainstem. It would be 

useful to determine if steady flows affect this rates, and if discharge and 

steady flows affect this rate (this is particularly applicable for the 

temperature control device). 

 

 Ho: Near shoreline temperatures in structurally complex habitats will not differ 

significantly from those observed for the mainstem. 

The intent of steady flows is to warm shoreline low velocity environments, 

if the amount of warming is negligible then perhaps temperature along the 

shoreline is not a limiting factor for recruitment of native fish, but low 

velocities are. 

 Ho: Thermal input from tributaries will not contribute significantly to the 

increase in mainstem temperatures during the LSSF. 

Tributaries are warm relative to the mainchannel, the low discharge in the 

mainstem coupled with the instream flow from the tributaries may affect 

mainstem warming, or at least provide a gradient of warming at the 

confluence. 

 Ho: Turbidity levels will remain constant during the LSSF experiment. 

Turbidity does affect sight feeders like trout and affects photosynthetic 

activity (primary productivity). Interactions between this physical 

variable and the biotic components may affect growth of fish or predation 

rates. We are not recommending predator-prey studies at this time, but do 

advocate determining a relationship between flow and suspended sediment 

(turbidity). 

2. Hypotheses addressing biotic habitat questions 
 Ho: Backwater number and total area will not differ significantly from values 

measured during previous fluctuating flows at equivalent stages. 

Historic data regarding backwaters is associated with fluctuating flows 

and documented by overflights at 8,000 cfs. Antecedent conditions may 

not effect backwater number and areas at 8,000 cfs. 

 

Ho: Backwater number and total area will not differ significantly throughout 

the period of steady flows. 

 

 Addresses sedimentation rates in eddy return current channels and the 

change in backwaters over time. Do they become less available over 

time? 

 Ho: The proportion of macro-habitat characteristics (near shoreline, hydrologic 

and substrate units) will not differ significantly from those observed at 

higher flows. 

The question is if all shoreline types and hydrologic units are 

proportionately represented under all flows. Addresses the question of 

does discharge matter, if all the same macro-habitats are proportionately 

still available? 

 Ho: Germination and densities of Tamarix ramosissima will not significantly 

differ from preceding years during fluctuating flows. 

Tamarisk and other exotic species may be advantaged by the high spring 

discharge and low steady flow regime resulting in increased shoreline of 

tamarisk seedlings and eventually tamarisk encroahment along shorelines 

of camping beaches. 

3. Hypotheses addressing productivity (primary and secondary) questions 

 Ho: There will be no significant difference observed in the benthic or 

macrophytic community for biomass or composition due to spike flow 

treatments. 

The 31,000 cfs spike has been suggested to be of sufficient magnitude to 

negatively affect aquatic food base biomass and composition, particularly 

in the fall. The effect needs to be determined. 

 Ho: There will be no significant difference in biomass, densities or 

composition observed for the benthic and macrophytic communities due to 

a LSFF treatment. 
Low steady flows may increase water clarity and allow for increase 

productivity, but the area available for productivity may be decreased by 

discharge, and result in no significant increase or change in the benthic 

and macrophytic community. 

 Ho: The quantity and composition of drift will not significantly vary during the 

duration of the LSFF treatment. 

Fluctuating flows are suggested to help maintain drift downstream by 

causing desiccation and subsequent renewed growth. If this is true, one 

would see a decline in quantity of drift over time under steady flows. Also 

the composition of the drift may change over time associated with different 

rates of senescence of benthos and macrophytes and tributary inputs. 

 Ho: The quantity and composition of drift during a LSFF treatment will not 

significantly vary in comparison with years of other steady or fluctuating 

flows. 

 

Does magnitude of discharge matter or pattern of discharge affect drift 

quantity or composition? This hypothesis collects the same data as the 

above hypothesis, but compares it to other flows. 

 

 Ho: There is no lag time in the rate of colonization for C. glomerata and 

epiphytes. 

 Does time since exposure affect colonization rates of cladophora. If 

colonization rates are the same for similar substrate subjected to different 

levels of exposure, then other factors may be affecting colonization. 

4. Hypotheses addressing fish response questions. 

 Ho: Relative frequencies (CPUE) of young-of-year native and non-native fish 

species in rearing habitats will not differ significantly during the LSSF, 

BHBF nor in comparison with prior fluctuating flow periods. 

Steady flows are assumed to be beneficial to young-of-year fish. If stable 

environments foster survivorship of young fish relative frequency should 

increase, provided sampling effort is sufficient to capture this information.

Ho: Relative frequencies (CPUE) of young-of-year native and non-native fish 

species will be the same in all rearing habitats during steady flows. 

Does the pattern of occurrence of young-of-year fish change among 

shoreline habitats or are all shoreline habitats used equally by young-of-
year. This may help determine if one habitat type is used 

disproportionately more than another. 

 Ho: Condition factor of native and nonnative fish species will not change 

significantly during the experimental flow period. 

Condition factor is a measure of food availability over time and is most 

likely to be reflected in older fish. 

 Ho: Spike flows preceding and following steady flow conditions will not 

actively displace non-native fish species in near shoreline nor backwater 

habitats for prolonged periods of time. 

Spike flows of a magnitude of 31,000 cfs are recommended to remove 

small bodied exotics and reduce the competitive advantage these species 

may have incurred over the course of steady flows. 

 Ho: Relative frequency of YOY trout will not vary significantly during the 

entire experimental flow period inclusive of spike and LSSF. 

Reduced available habitat and food resources in the Lees Ferry reach may 

exclude young-of-year and may result in reduced number (i.e, relative 

frequency) of young-of-year compared to baseline data. 

Suggested hydrograph 

 Because of the uncertainty associated with basin hydrology, reservoir filling and 

potentials for spills, and questions about pooling levels and spikes, we suggest the 

following: 

1. March discharges that will ensure low, steady flow in June – September. 

2. An April/May hydrograph that reaches at least 17,500 and does include a 

spike, but that also includes a shoulder of 15 and 12,500 on the descending 

limb of one day each. This will allow area, velocity and temperature at 

tributary mouths at different discharges to be evaluated and compared. The 

limb of 15 and 12,500 should be of sufficient duration to allow surveying of 

these parameters (4 days). (Serves as a review component of the hydrograph) 

3. If the hydrology by May indicates that low steady flows (8,000 cfs) are not 

possible, then steady flows at any discharge would be informative, but may 

have greater implications for sediment budgets as volumes increase and may 

compromise some data collection efforts. 

4. Include the fall spike to determine if small bodied exotics are displaced and to 

determine the effect on the food base in Lees Ferry. The effect of exotic 

displacement will be evaluated on the winter fish monitoring trip, so motor 
use in non-motor season will not be an issue. (Serves as a review component 

of the hydrograph). 

Under this hydrograph, data collection, beyond already planned monitoring trips, will 

potentially not start until approximately a week prior to the spring spike, to document 

pooling at a high steady discharge level. Monitoring of fish in the LCR will be taking 

place in mid-April, and we can redirect efforts around this ponding event, to some extent. 

Development of Research Plan with associated hypothese

 GCMRC recommends using the expertise of researchers to help develop plans of 

study around the hypotheses listed above. We will collaborate with these researchers to 

develop a plan that will adequately address the hypotheses. In some cases, portions of 

the plan will be covered by an existing monitoring trip, but may need to be augmented by 

additional trips. In other cases additional trips may be required to address the hypotheses. 

We would modify existing cooperative agreements and use unsolicited proposals to 

develop cooperative agreements for new contractors. 

Schedule for Planning. 

February 25 Send out science plan draft document to contracted researchers. 

Researchers develop preliminary study plan for hypotheses pertinent to 

their expertise. 

February 28- 

March 2 Contact researchers to determine methods, logistics, and budgets. 

March 6 Provide BOR and WAPA with estimated costs for steady flow work. 

March 5-10 BOR determines if steady flows will occur and provides the hydrograph. 

March 15-20 Submit modifications to contracts for funding. Submit modified logistics 

schedule to Park Service. 
3-1-00 B. Ralston 

Presented at TWG Meeting 3/2 - 3/3/00 

O:/smankiller/wp70/Meetings Main/TWG Main/TWG Ad Hoc Groups-Teams/Science Plan WY2000 LSSF/LSSF Plan 

Rev 3-1-00 BRalston.doc