Project A: Streamflow, Water Quality, and Sediment Transport and Budgeting in the Colorado River Ecosystem
Project Summary and Purpose
The primary linkage between Glen Canyon Dam operations and the characteristics of the physical, biological, and cultural resources of the Colorado River ecosystem (CRe) downstream from Glen Canyon Dam is through the stage, discharge, water quality, and sediment transport of the Colorado River. This project makes and interprets the basic measurements of these parameters at locations throughout the CRe. Project A thus collects the physical data that directly link dam operations to all resources in the downstream CRe. The data collected by this project are used to implement the High-Flow Experiment (HFE) Protocol (i.e., trigger and design HFE hydrographs), to evaluate the segment-scale sand mass-balance response to the HFE Protocol (U.S. Department of the Interior, 2011; Grams and others, 2015), and to evaluate the downstream effects of releases conducted under the Long-Term Experimental and Management Plan (LTEMP) Environmental Impact Statement (EIS) (U.S. Department of the Interior, 2016a, b). Two of the metrics proposed to evaluate LTEMP management for sediment are measured by this project.
Hypotheses and Science Questions
There are two key hypotheses that guide the long-term monitoring and research conducted under all elements of Project A. These hypotheses directly address the LTEMP sediment goal and the nine other LTEMP goals listed in the previous section.
- Glen Canyon Dam can be operated such that the sand resources in the CRe are sustainable.
- Glen Canyon Dam can be operated such that the other CRe resources affected by dam operations can be sustainably managed.
In this usage, “dam operations” refers to the amount and quality of the water released from the dam, where “amount” refers to stage and streamflow, and “quality” refers to temperature, salinity, turbidity, and dissolved oxygen.
These hypotheses are paraphrased from the LTEMP EIS and from earlier goals, information needs, and strategic science questions formulated by the GCDAMP. The first of these two guiding hypotheses is tested using the continuous mass-balance sand budgets (Project Element A.3) constructed using 15-minute streamflow data (Project Element A.1) and suspended-sand data (Project Element A.3). Annual updates on the status of the segment-by-segment testing of the first hypothesis are provided at each Annual Reporting Meeting. Although the second hypothesis guides data collection in Project A, this hypothesis is tested by the other GCDAMP-funded projects, with annual updates provided by these other projects.
Project Element A.1. Stream Gaging and Hydrologic Analyses (Ongoing Study)
This element partially funds the collection, serving, and interpretation of continuous 15-minute measurements of stage and discharge on the main-stem Colorado River at USGS streamflow gaging stations located at river miles (RM) 0, 30, 61, 87, 166, and 225, and at gaging stations on the major tributaries and in a representative subset of the smaller tributaries (Topping and others, 2021). Eighty percent of the budget for Project Element A.1 funds salary for the field and office time required to operate gaging stations and funds the office time for serving data and working on peer-reviewed interpretive publications.
Project Element A.2. Continuous Water-Quality Parameters (Ongoing Study)
This element funds the collection, serving, and interpretation of continuous 15-minute measurements of water temperature, specific conductance (a measure of salinity), turbidity, and dissolved oxygen at the outlet of Glen Canyon Dam and at the above-mentioned six main-stem Colorado River gaging stations. This element also funds episodic measurements of specific conductance associated with suspended-sediment samples collected in tributaries (these measurements are intrinsic to the laboratory methods for processing the suspended-sediment samples and therefore cost nothing). Seventy-three percent of the budget for Project Element A.2 funds salary for the field and office time required for making the water-quality measurements and funds the office time for serving the data.
Project Element A.3. Sediment Transport and Budgeting (Ongoing Study)
This element funds the collection, serving, and interpretation of continuous 15-minute measurements and episodic measurements of suspended sediment and bed sediment at the above-mentioned gaging stations on the Colorado River and its tributaries. In addition, this project element funds interpretive work in regard to the sand supply from the Paria and Little Colorado rivers, and interpretive work in regard to the effect of dam operations on the sediment resources in the Colorado River between Glen Canyon Dam and Lake Mead.
Project B: Sandbar and Sediment Storage Monitoring and Research
Project Summary and Purpose
The purposes of this project are to a) track the effects of individual High-Flow Experiments (HFEs) on sandbars and campsites, b) monitor the cumulative effect of successive HFEs and intervening operations on sandbars and sand conservation, and c) investigate the interactions between dam operations, sand transport, and eddy sandbar dynamics. These objectives are accomplished by annual measurements at long-term sandbar monitoring sites (B.1), measurements of changes in riverbed sand storage and studies of riverbed dynamics (B.2), maintenance of a geodetic control network (B.3), and development of streamflow, sediment transport, and sandbar response models (B.4). Field activities that would occur for monitoring condition-dependent experimental actions such as HFEs are also described (B.5). Results from the monitoring elements of this project are used to evaluate progress towards meeting the Long-Term Experimental and Management Plan (LTEMP) goal, to “Increase and retain fine sediment volume, area, and distribution in the Glen, Marble, and Grand Canyon reaches above the elevation of the average base flow for ecological, cultural, and recreational purposes.” (U.S. Department of the Interior, 2016). The models developed and maintained in this project are used to plan and design HFEs and to forecast the response of sediment and sandbars to potential flow scenarios for long-term planning.
Hypotheses and Science Questions
- Can sandbar building during HFEs exceed sandbar erosion during periods between HFEs, such that sandbar size can be increased and maintained over several years?
- What is the long-term effect of dam operations, including controlled floods, on the size of eddy sandbars at 45 long-term monitoring sites above the 8,000 ft3/s stage?
- How do these changes affect the following recreational and ecosystem resources: camping beaches, substrate for riparian vegetation, and areas of bare sand that are redistributed by wind to upslope locations?
Project Element B.1. Sandbar and Campsite Monitoring with Topographic Surveys and Remote Cameras (Ongoing Study; Partially Funded)
We will conduct topographic measurements at 45 long-term monitoring sites (Hazel and others, 2022) that will be used to compute sandbar area and volume at each of these sites (Figure 1) and usable campsite area (Hadley and others, 2018) at a subset of 37 sites. The monitoring sites were selected between 1990 and 2002 to represent the range of sandbar types with sites distributed throughout Marble and Grand Canyons such that measurements can be made at all sites on a single annual river trip. Although these study sites comprise less than 10 percent of the subaerially exposed sandbars of similar type in all of Grand Canyon (Hazel and others, 2022), they have been shown to be representative of a larger sample of sandbars of similar type in Lower Marble Canyon and Eastern Grand Canyon (Hazel and others, 2022).
Project Element B.2. Bathymetric and Topographic Mapping for Monitoring Sediment Storage and Riverbed Dynamics (Ongoing Study; Partially Funded)
The primary purpose of this project element is to track trends in sandbar conditions and sand storage throughout Grand Canyon over the time scale of LTEMP to provide an evaluation of whether the supply of sand (the sum of recent tributary inputs and background storage) necessary for building sandbars is increasing, decreasing, or stable and a robust measure of high-elevation sandbar change. The important distinction between B.1 and B.2 is that the measurements made in Project Element B.2 include a much larger sample of sandbars than included in the B.1 annual sandbar monitoring and that the measurements in B.2 include both exposed sandbars and sand that is submerged in the river channel.
Project C: Riparian Vegetation Monitoring and Research
Project Summary and Purpose
This project focuses on riparian plant communities, particularly how dam operations can be used to control plant composition and cover and how plant communities impact other valuable, managed resources. The proposed elements in this project address Goal 11 of Glen Canyon Dam Long-Term Experimental and Management Plan (LTEMP) (U.S. Department of Interior, 2016), LTEMP, which is related to maintaining diverse native riparian plant communities and quality wildlife habitat.
Project Element C.1. Ground-based Riparian Vegetation Monitoring (Modified Study, Partially Funded)
The monitoring protocol is described in detail in Palmquist and others (2018b) and monitoring results through 2019 are described in Palmquist and others (2023). The random sampling effort collects data annually at 80-100 sites between Glen Canyon Dam and river mile 240, where the influence of Lake Mead becomes apparent on the shorelines. As part of the experimental design, new sites are selected each year. This data set provides a full representation of the plant communities affected by Glen Canyon Dam. The long-term monitoring sandbar sites are 45 large sandbars that are sampled each year. These sites are not representative of the riparian communities across the entire CRe (Palmquist and others, 2023), but are important recreational sites and the sites used for evaluating the state of sand resources (Hazel and others, 2022).
Project Element C.2. Mechanistic Experiments with Plant Species of Interest (Modified Study)
We intend to expand on the pilot greenhouse experiment in several ways. First, we will increase replication to improve statistical power to identify treatment effects. Second, we will increase the size of our experimental containers to simulate more realistic stage fluctuations. Third, we will assess multiple stages of plant demography, including germination, establishment, and growth. For the latter, we will utilize larger plants that allow us to make destructive measurements of leaf or stem water potentials without harming the plants, which was not feasible with the pilot experiment. In short, we propose to develop larger, more robust infrastructure for conducting daily fluctuation experiments that will be relevant to real-world conditions. We acknowledge that these proposed experiments do not capture effects of variations in velocity, shear stress, sediment transport, or directionality that would occur in a river during flow fluctuations. We hope to combine the results of the proposed, controlled experiments with other research (Butterfield and others, 2020; Project C.4 in this proposal) to gain a more comprehensive picture of the impacts of daily fluctuating flows on riparian ecosystems in the CRe.
Project Element C.3. Predictive Modeling of Vegetation Responses to Dam Operations (Modified Study, Partially Funded)
This project element will conduct forward-looking modeling efforts to identify the flow conditions that would optimize the vegetation objectives listed in Goal 11. Lags in vegetation responses to hydrological events and the lack of interannual flow variability in the CRe create the need to use data derived from regional collaborations and manipulative experiments that expand the range of biophysical parameters used to construct vegetation models. This project element will integrate ground-based vegetation monitoring (Project Element C.1), manipulative experiments (Project Element C.2), and existing regional data on riparian vegetation composition and hydrographs using advanced statistical modeling.
Project Element C.4. Biogeomorphic Linkages between Streamflow, Sediment Transport, and Vegetation Composition (New Study, Partially Funded)
We propose to conduct a multi-phased, interdisciplinary study aimed at quantifying large-scale changes to channel morphology relative to vegetation change. The work in Project C.4 will leverage datasets produced by Project Elements L.1, Project B.4 (unfunded), and Project D.2 to evaluate changes in the biogeomorphic condition of the river corridor (see Figure 6 for project linkages). Project C.4.1 will build upon Butterfield and others (2020) and Durning and others (2021) by investigating whether large-scale changes in vegetated area and species have had a corresponding impact on river channel form, predominantly channel width. This will be done using a large suite of remote sensing data collected by Project L between 2002 and 2021. These findings will be linked to historical photograph comparisons made in Project Element D.2 that depict changes in the shape of the channel banks, which may indicate whether channel changes visible in the aerial photographs have also corresponded to changes in floodplain elevation, and bank steepness. Project Element C.4.2 will implement field measurements of plant traits within a 2-dimensional hydraulic model to specifically analyze how effective individual vegetation species are at causing channel change by altering channel-margin/floodplain hydraulics and sediment transport. C.4.2 will build upon Butterfield and others (2020) and leverage hydraulic model development conducted in Project B.4 (unfunded). Both phases of work will provide needed information regarding vegetation management actions throughout the river corridor.
Project D: Effects of Dam Operations and Experimental Vegetation Management for Archaeological Sites
Project Summary and Purpose
Archaeological site monitoring results illustrate some of the negative impacts of human river management and associated gully erosion on site condition and the physical integrity of prehistoric and historic archaeological sites. However, monitoring and research also demonstrate that windblown river sand can help to offset erosion impacts on archaeological site condition (Sankey and others, 2023). Targeted riparian vegetation removal on sandbars may provide an environmental management opportunity to increase windblown sand supply from sandbars to archaeological sites, and thus increase in-situ preservation potential on a site-specific basis, while also helping to maintain the historic geomorphic context of these cultural resources and improve conditions for native, psammophilous (i.e., sand-loving) species. Effectiveness of vegetation management might theoretically be increased when coupled with HFEs to rebuild sandbars, or with periodic low river flows to expose sandbars, which in both cases are the sources of windblown sediment supply. In 2023, for the first time, experimental vegetation management and an HFE were implemented in combination in the same year in Grand Canyon. Without environmental management actions to increase in-situ preservation potential, sites along the Colorado River will likely continue to erode (Figure 1), leaving excavations or other mitigation of individual affected sites (e.g., Thorne, 1991), as the only options for preserving archaeological site information before it is lost, although this approach falls short of stated environmental-management goals and also conflicts with some tribal values.
Project Element D.1. Monitoring the Effects of Dam Operations on Archaeological Sites (Modified Study)
During FY 2025-27, GCMRC will continue long-term monitoring of archaeological sites using lidar to report on proposed LTEMP Cultural Resources Performance Metric 1.2 Lidar Topographic Change Detection. The purpose of this monitoring is to quantify the effects of dam operations and other factors on the geomorphic condition of a sample of archaeological sites in the Colorado River corridor in Grand Canyon National Park and Glen Canyon National Recreation Area that are within the area of potential effect of Glen Canyon Dam operations. Geomorphic changes are determined from ground-based lidar topographic surveys (also termed terrestrial laser scanning, TLS).
Project Element D.2. Monitoring Landscape-Scale Ecosystem Change with Repeat Photography (Ongoing Study)
During FY 2025-27, GCMRC will continue compiling a photographic record and associated database of ecological and geomorphic changes affecting the landscape and archaeological sites within the river corridor using well-established repeat photography methods.
Project Element D.3. Evaluating Effects of LTEMP Non-Flow Actions and other Experimental Vegetation Management on Archaeological Sites (Modified Study)
GCMRC will collaborate with NPS, the Hopi Tribe, and any other parties that express interest, to study effects of experimental vegetation management, with a specific focus on LTEMP non-flow actions that may affect archaeological site preservation.
Project E: Controls on Ecosystem Productivity: Nutrients, Flow, and Temperature
Project Summary and Purpose
In this workplan, we propose to revise three elements from the prior FY 2021-23 workplan (Project Elements E.1, E.2, and E.4). A new element (currently unfunded) focuses on ecosystem metabolism in the Western Grand Canyon (E.3). Several sub-elements propose to analyze data collected during the last work plan (mass balance P budgeting in E.1; vegetation mapping in Glen Canyon and GPP modeling exercises in E.2 (unfunded); bioenergetics modeling in E.4). One new sub-element proposes to survey benthic diatom populations in Grand Canyon and establish a modern molecular baseline for their abundance and distribution (E.2)
Project Element E.1. Phosphorus Budgeting in the Colorado River (Ongoing Study; Partially Funded)
This project will consider major sources and potential sinks for P in the CRe using a P mass balance approach.
The capability to model river P concentrations based on suspended sediment concentrations will inform GPP modeling efforts described in E.2, allowing us to link P to rates of primary production (especially in further downstream sections where tributary inputs potentially override the influence of variation in the P in dam releases). The element will also support our broader ability to hindcast (and possibly even forecast) P dynamics, which will improve our understanding of linkages between climate, P and the food web.
Project Element E.2. Rates and Composition of Primary Producers in the Colorado River (Modified Study; Partially Funded)
We will continue developing estimates of GPP at the daily timestep to add to the continuous record that has been developed at the USGS gaging stations.
This project element provides the underlying modeling to support the natural processes GPP metric and aims to disentangle the drivers of both rates and types of riverine primary production and their link back to fish production. This project will also help clarify how resilient the diatom base of the food web is to recent environmental change. It will establish a modern (molecular) baseline for the abundance and distribution of this important producer group throughout the canyons, including for salient, ecologically relevant taxa such as nitrogen-fixing (e.g., Epithemia spp.) and nuisance bloom-producing diatoms (Figure 2).
The unfunded vegetation mapping project would provide a machine learning model that could be used to classify images and produce maps of submerged aquatic vegetation in Lees Ferry. Such maps could serve as a baseline to answer questions related to the effects of dam operations and reservoir conditions on dominant primary producers that fuel the “green” food web consumed by aquatic invertebrates and fishes.
Project Element E.4. Linking Ecosystem Metabolism to Higher Trophic Levels (Ongoing Study)
This project element will integrate data on primary production, insect drift, fish growth, and population size to understand trophic linkages and better predict how the ecosystem will respond to changes in nutrients, temperature, and flow. The improved understanding of species-specific respiratory physiology will help predict how changes in dam operations will influence growth and production of native and nonnative fish species.
- Humpback chub and flannelmouth sucker have lower basal metabolic demands than related taxa.
- If humpback chub and flannelmouth sucker have lower basal metabolic demands than related taxa, the ecosystem can sustain large populations of these species despite relatively low primary production and these species can survive through relatively extended periods of low food availability.
- Native fish species in the Western Grand Canyon may be approaching abundances at which food limitation becomes more important in regulating population dynamics.
Project F: Aquatic Invertebrate Ecology
Project F is tracking ecosystem response to the Bug Flows experiment and other ongoing or potential management actions using community science monitoring of aquatic insects (F.1), monitoring of invertebrate drift (F.1 and F.2), monitoring of invertebrate communities in tributaries and the mainstem Colorado River using environmental-DNA (eDNA; F.3), and quantifying feeding habits, parasite loads, and overall health of native and nonnative fishes using DNA analysis of feces and stable isotope analysis of fin clips (F.4). To reduce costs and facilitate processing of existing samples and analysis and synthesis of existing data, we are proposing to reduce all monitoring and sample collections, and some sample collections will be discontinued entirely (e.g., all bat monitoring will be discontinued, sticky trap and light trap sampling in Glen Canyon will be discontinued, and annual collections of invertebrate drift samples throughout Grand Canyon will be discontinued).
Project Element F.1. Aquatic Invertebrate Monitoring in Marble and Grand Canyons (Modified Study; Partially Funded)
The main thrust of F.1 is the community science monitoring of emergent aquatic insects, where river guides, education groups, private boaters, and other members of the public deploy a simple light trap each night in camp in a standardized fashion to collect samples of adult aquatic insects that have emerged from the Colorado River. We propose to continue collecting invertebrate drift samples at the Juvenile Chub Monitoring site during those trips to provide data on invertebrate prey availability to inform humpback chub models.
Project Element F.2. Aquatic Invertebrate Monitoring in Glen Canyon (Modified Study; Partially Funded)
This element is a continuation of a Glen Canyon monitoring program that has been ongoing since 2007. The proposed study design (4 sampling bouts per year, 5 locations per bout) represents a reduction in monitoring effort to reduce costs compared to the ~monthly monitoring that has been conducted since 2007.
Project Element F.3. Aquatic Invertebrate Monitoring in the Colorado River and Grand Canyon Tributaries (Ongoing Study; Funded)
eDNA monitoring of tributary streams is relevant to management, because these streams are important spawning and rearing habitat for native fishes, and some are also sites of humpback chub translocations. For this reason, understanding the diversity of aquatic food base resources available to these fishes can influence decisions about whether to translocate more fishes into these streams, and in identifying candidate streams for future translocations. Further, tributaries represent sources of aquatic insects that could recolonize the mainstem Colorado River.
We hypothesize that:
- H4: Tributaries support more diverse invertebrate and parasite communities compared to the mainstem Colorado River.
We will also evaluate what factors explain variation in invertebrate and parasite diversity across tributaries with a focus on the potential role of water quality conditions (e.g., pH, alkalinity, heavy metals, nutrients). Better understanding the factors that control the diverse invertebrate assemblages that are present across different tributaries will provide insight into the role that water quality may play in promoting or limiting colonization of the mainstem Colorado River by tributary invertebrates.
Project Element F.4. Fish Diet and Health Studies (Ongoing Study; Funded)
Owing to numerous changes in the food base and fish communities since the last detailed food web studies ~15 years ago, we will assess feeding habits of flannelmouth sucker, humpback chub, rainbow trout, and smallmouth bass. We will focus on non-lethal methods in line with tribal concerns regarding the taking of life. Specifically, we will collect fin clips from fishes to analyze for stable isotopes, and we will collect fecal samples for DNA analysis. Carbon and nitrogen stable isotope analysis of fin clips provide a non-lethal indication of long-term feeding habits (i.e., recent months) including the trophic position of fishes and the relative importance of algae vs. terrestrial detritus to fish production overall (Layman and others 2012). This long-term information on general feeding habits obtained from stable isotopes complements the more detailed, species-level, snapshot of feeding habits that we will obtain from DNA analysis of fish feces (i.e., what the fish ate that day). This detailed information concerning species presence/absence in diets, when combined with direct eDNA measurements of invertebrate distributions across the Colorado River ecosystem (F.3, above), can be used to estimate source and contribution (tributary vs. mainstem, with tributary identity and mainstem river mile location as cofactors) of the invertebrate food base to fish feeding habits. Because our eDNA methods also detect DNA from terrestrial insects when present, we will be able to quantify the proportion of terrestrial vs. aquatic-origin insect species in fish diets.
Project G: Humpback Chub Population Dynamics Throughout the Colorado River Ecosystem
Project G includes project elements to estimate abundances required by the 2016 Biological Opinion (G.1, G.2, G.3, G.4) by monitoring humpback chub in the LCR-spawning population by sampling the LCR and JCM-east reach in the Colorado River (Project Elements G.2, G.3). Additionally, this project includes sampling in western Grand Canyon via continuation of mark-recapture in the JCM-west reach (210.5-214 river miles downstream of Lee Ferry) and extensive spatial sampling via the aggregation trips (Project elements G.5, G.6). Mark-recapture data from these trips will be supplemented with data from autonomous PIT tag antennas (Project Elements G.4, G.9), such as the LCR multiplexer array and submersible antennas, as these technologies have proven effective at detecting larger adults. Data collected from the above-mentioned field efforts will be analyzed to help learn more about humpback chub life history and to guide management efforts (Project Element G.1).
Project Element G.1. Humpback Chub Population Monitoring (Ongoing Study; Partially Funded)
We will develop and refine models using data from existing (and ongoing) field sampling to help inform management efforts and conservation actions for humpback chub. Proposed foci for modeling efforts may include 1) estimating abundance of various size classes in the LCR-spawning population as defined in the 2016 Biological Opinion (e.g., Figure 6; U.S. Fish and Wildlife Service, 2016), 2) including antenna detections from a wide geographic area in Grand Canyon to obtain a better estimate of adult survival in JCM-west (i.e., to differentiate emigration from mortality), 3) estimate abundance of humpback chub adults in western Grand Canyon based on data collected by humpback chub aggregations sampling trips, and 4) estimate the effects of environmental covariates on demographic parameters (e.g., survival, growth, movement), which may help predict humpback chub responses to management actions and future scenarios, and 5)
developing an occupancy model that accounts for detection probability to look at long-term, large-scale changes to humpback chub distribution with the Colorado River ecosystem.
Project Element G.2. Annual Spring/Fall Abundance Estimates of Humpback Chub in the Lower 13.6 km of the LCR (Ongoing Study)
The USFWS has been conducting four sampling trips into the LCR each year since 2001, and this data set is used to estimate humpback chub abundance at different life stages. These abundance estimates document substantial temporal changes to adult population size since 2000, most notable of which is the increase in adult abundance that has occurred since 2007. While all four trips sample all life stages, spring trips generally inform adult (Figure 7), large subadult, and age-1 abundance estimates in the LCR, as well as provide information about the migratory component of LCR-spawners, whereas the fall trips provide estimates of age-0 abundances in the LCR and abundances of LCR residents (Van Haverbeke and others, 2013).
Project Element G.3. Juvenile Chub Monitoring (JCM) near the LCR Confluence (Ongoing Study)
This project element is a continuation of previous monitoring work that commenced in 2012 and includes three annual sampling trips to the JCM-east reach (located 62.7-66.0 river miles downstream of Lees Ferry) as well as one annual sampling trip to the lower LCR (July) to estimate abundance and outmigration of age-0 humpback chub born the previous spring. Because these trips visit fixed sites and use mark-recapture methods, this project element provides information about demographic processes, such as survival and growth (Dzul and others, 2016, Dzul and others, 2023) as well as abundances (Dzul and others, 2021b).
Project Element G.4. Remote PIT Tag Array Monitoring in the LCR (Modified Study; Partially Funded)
PIT-tag arrays read and record codes from tagged fish that swim over antennas anchored to the river bottom or riverbank. Accordingly, these arrays provide a method for boosting recapture events without requiring additional fish handling (Figure 9). Importantly, these systems are particularly useful for detecting large (>250mm TL) humpback chub which are difficult to capture using hoop nets (Dzul and others, 2021a, 2024). In the LCR, models without antenna data underestimated the proportion and number of migratory adult humpback chub that moved into the LCR in spring months and also underestimated adult survival compared to models with these data (Dzul and others, 2021a). Taken together, these results illustrate that the benefit of including PIT-tag arrays is not solely based on their ability to increase detection probabilities for all humpback chub (Figure 9), but rather their ability to increase detection of a subset of the humpback chub population that is relatively invulnerable to capture.
Project Element G.5. Monitoring Humpback Chub Aggregation Relative Abundance and Distribution (Ongoing Study; Partially Funded)
This project will conduct one mainstem sampling trip per year focused on aggregations sites. The annual aggregations trip will focus on hoop net monitoring of the known aggregations (e.g., RM 30-36, LCR, Bright Angel, Shinumo, Stephens Aisle/Middle Granite Gorge, Havasu, Pumpkin Spring) as well as other sites that are targeted for biological interest. Project Element G.5 funds an additional boat that can be used to seine backwaters to monitor juvenile humpback chub and warm-water nonnatives (funded in FY 2025 and FY 2026, not funded in FY 2027).
Project Element G.9. Movement in Western Grand Canyon from System-Wide Antenna Monitoring (New Study; Partially Funded)
Submersible antennas that could be deployed on numerous scientific trips (e.g., Arizona Game and Fish system-wide fish monitoring trips that randomly sample reaches) and also deployed by river boatmen as part of a citizen science project to help collect data about movement of fishes. Due to cost increases and funding limitations, this project element is currently proposed to be funded only in FY 2025.
Project H: Salmonid (Trout) Research and Monitoring Project
This research project proposes to evaluate 1) the effect of ongoing ecological changes (i.e., temperature, DO, warm-water species expansion) on trout somatic growth, reproduction, recruitment, and survival, 2) effects of spring and fall high flow events (HFEs) on trout recruitment, dispersal, and growth, 3) factors controlling trout recruitment and dispersal into Marble Canyon and Little Colorado River (LCR) reaches, 4) factors controlling the quality of the trout fishery (growth, condition, sexual maturity, and angler catch rates), and 5) factors regulating brown trout and other nonnative fish population dynamics, as well as efficacy of an incentivized brown trout harvest program.
Project Element H.1. Rainbow Trout Fishery Monitoring in Glen Canyon (Modified Study)
Data collected under this element will be used to calculate metrics on the angling experience for both boat and walk-in anglers, including relative angler use, angler catch per unit effort values, and a rating of the fishery. AGFD angler surveys also provide information for Project J. The Lees Ferry Creel Survey and Arizona Game and Fish Department (AGFD) Citizen Science Project (FY 2021-23 and previous TWPs), which directly evaluates the quality and changes in the recreational experience of angling in the rainbow trout fishery in the Lees Ferry, Glen Canyon National Recreation Area is proposed to continue.
Project Element H.2. Trout Reproductive and Growth Dynamics (Modified Study)
This is the field data collection component of the research project referred to as the Trout Reproductive and Growth Dynamics (TRGD) project, involving mark-recapture monitoring, as described below, is designed to determine the effects of LTEMP ROD flows on the recruitment of young-of-year (YOY) rainbow and brown trout in Glen Canyon, growth rates of juvenile and adult trout, and dispersal of YOY trout from Glen Canyon to Marble Canyon.
Project Element H.3. Salmonid Modeling (Ongoing Study)
Project Element H.3 will address science questions identified below, through analysis of data collected in H.1 and H.2. Most of the science questions, as originally proposed in the FY 2021-23 TWP (U.S. Department of the Interior, 2020) and extended in FY 2024, remain relevant now; however, we have revised the list, placing more emphasis on changing environmental conditions and brown trout, because of the relatively unclear risk posed by this species, new expansion of warm-water nonnative species, and recent declines in both trout populations in Glen Canyon.
- What are the effects of changing conditions downstream of Glen Canyon Dam (i.e., DO, water temperature) on trout recruitment, growth, and survival?
- What are the effects of flow experiments and other management actions (removals or flow management to suppress warm-water nonnative species) on trout population dynamics?
- What controls rainbow and brown trout dispersal from Glen Canyon downstream into Marble and Grand canyons?
- What factors control the quality of the rainbow trout fishery, and how does electrofishing capture efficiency influence interpretation of rainbow trout fishery metrics?
- How do expansions of warm-water nonnative fish species influence trout population dynamics?
- What factors regulate brown trout population dynamics in Glen Canyon, and what is the management efficacy of control actions?
- How is climate change likely to impact the rainbow trout fishery below Glen Canyon Dam in short- and longer-term periods?
- Are certain operations of Glen Canyon Dam more conducive than others to allow long-term coexistence of a high-quality rainbow trout fishery with downstream native fish species?
Project I: Nonnative Aquatic Species Monitoring and Research
We will focus our research and monitoring efforts on detecting new or notable increases and/or distributional shifts in nonnative species using genomic tools to determine nest origin and potentially the abundance of nonnative fishes being removed from the river, conduct enhanced biosurveillance through additional trips and environmental DNA (eDNA) monitoring, assess entrainment potential for nonnative fishes in Lake Powell, and analyze data from federal and state partners to assess the efficacy of management actions to control nonnative populations of smallmouth bass.
Project Element I.1. System-wide Native Fishes and Nonnative Aquatic Species Monitoring (Ongoing Study)
The objective of this project element is to provide long-term data on the longitudinal distribution and status of the fish assemblage in the mainstem Colorado River from Lees Ferry (RM 0) to Pierce Ferry Rapid (RM 281). We will use a combination of standardized electrofishing, hoop netting, and angling to sample the native and nonnative fish community. In the FY 2025-27 TWP, AGFD will conduct one spring sampling trip annually from Lees Ferry to Pearce Ferry and add a new system-wide sampling trip in fall that is timed when nonnative detections are likely to be highest during the warmest reservoir release months of the year.
Project Element I.2. Estimating Kinship and Spawner Abundance of Warm-Water Nonnatives (New Study; Partially Funded)
The objective of this project element is to use kinship genetic analysis to better understand the ongoing expansion of smallmouth bass into Grand Canyon, determine the extent to which juveniles are locally produced or entrained from the reservoir, and potentially estimate spawner abundance and survival.
Project Element I.3. Identifying Emerging Threats to the Colorado River Ecosystem Using Environmental DNA (Modified Study; Partially Funded)
The objective of this project element is to conduct biosurveillance of nonnative species by collecting water samples and using molecular tools to identify high risk species of fish, crayfish, gastropods, and mollusks that are in the early stages of expansion or those that evade capture by traditional sampling techniques.
- I.3.2. How Comparable are eDNA Methods to Traditional Sampling Gear for Detecting Sources and Dispersal of Nonnative Fishes in the Colorado River? (Partially Funded)
Seining backwaters in the mainstem Colorado River (funded in FY 2025 only): Project Element G.5 adds an additional boat and boatman to the Fall USFWS Humpback Chub Aggregations Monitoring trip in September 2025 to search for nonnative species by seining backwaters during the warmest month of the year. Backwaters are often ephemeral and dependent on flows, but previous trips have targeted approximately 200 backwaters throughout Grand Canyon. We will collaborate with the USFWS by collecting up to three eDNA samples from selected backwaters where at least three seining passes are conducted.
Electrofishing in the Lees Ferry Reach (funded in FY 2026 only): The purpose of this sampling is to compare species detection and relative abundance in sites 1A & 1C by deploying a separate eDNA boat to passively collect water samples in each 250-m reach while electrofishing is occurring.
Electrofishing, hoop netting, and antennas in the mainstem Colorado River (funded in FY 2027 only): The purpose of this eDNA sampling is to compare fish detection and relative abundance (copy number) data to catch data collected during electrofishing, hoop netting, and passive PIT tag antenna sampling.
- I.3.4: What is the Incidence of Parasite Infestation in Humpback Chub in the Little Colorado River and Mainstem Colorado River? Can a Molecular Assay be Developed to Reduce Handling Time and Expand the Scope of Monitoring? (Partially Funded)
Continue traditional sampling methodology to monitor Asian fish tapeworm and anchor worm (Lernaea) in humpback chub as specified in the Environmental Commitments Section in the LTEMP ROD (and 2016 Biological Opinion).
Project Element I.4. Modeling Population Dynamics and Improving Forecasting Tools for Smallmouth Bass and Other Nonnative Fishes (New Study)
- I.4.1: How does turbidity and temperature affect feeding efficiency and survival of early life stages of smallmouth bass? How does adding turbidity as a parameter in the smallmouth bass population growth model affect performance?
- I.4.2: How effective are management actions (LTEMP Flow Experiments, removals) at reducing smallmouth bass population growth, survival, dispersal, and reproduction?
- I.4.3: What are the long-term drivers of distributional changes in native and nonnative fishes in the CRe?
Project J: Socioeconomic Research
- Recreational Experience: To support research and monitoring needs related to “recreational experience,” this project element will develop a model of whitewater recreation to predict access, participant behavior, and economic value of whitewater rafting under future low flow scenarios, in collaboration with the National Park Service (NPS), and
- Tribal Resources: To support research and monitoring needs related to “Tribal resources,” this project element focuses on improving integration of Tribal benefits knowledge, knowledge of benefits and well-being, arising from ecosystems and human engagement with ecosystems, in the GCDAMP (Hoelting and others, 2024a). The effort supports increased recognition and comprehension of the diverse forms of Tribal benefits knowledge that are available to inform GCDAMP decision-making through multiple learning pathways. This effort will be carried out in collaboration and co-production with Tribal led monitoring activities to ground the conversation in Tribal research frameworks.
Project Element J.1. Integrated Models for Adaptive Management
Continued development of integrated models will provide opportunities to assess the value of information gained from monitoring and research within the GCDAMP. The integrated modeling element will focus on integrated modeling of native and nonnative fishes in Glen and Grand Canyon, leveraging ongoing bioeconomic modeling of the system. The project element will emphasize the development of guidance for data collection efforts within the complex bioeconomic system with a continued focus on environmental flow research and hydropower operations at GCD, nonnative species monitoring efforts, management for viable endangered species populations, and other socio-economic stakeholder objectives. While we intend to utilize existing predictive models of biological and hydropower resources to evaluate the usefulness of monitoring and research, this project element will also undertake a structured value of information (VoI) analysis with a sub-set of downstream resources.
Project Element J.2. Recreation Monitoring and Research
Develop a simulation model of annual recreational rafting in Grand Canyon using a sub-daily model. The sub-daily model will be based on forecast hydrology, operational constraints at GCD, energy generation and recreational use as determined by NPS policy and forecast visitor use.
Project K: Geospatial Science, Data Management and Technology Project
The primary purpose of this project is to provide high-level support to GCDAMP-funded science efforts in the disciplines of geospatial science, data management, database administration, and emerging information technologies.
Project Element K.1. Enterprise GIS, Geospatial Analysis and Processing (Ongoing Study)
Continue to support research and monitoring projects by providing geospatial expertise to most projects on field mapping methods, development of customized maps, sample site unit definition and selection, GIS layer development and metadata review, Python programming, and GIS tool development and support.
Project Element K.2. Data Management and Database Administration (Ongoing Study; Partially Funded)
During the last three years this project has worked towards addressing the need to expand concepts developed in GIS to other data resources across GCMRC. This includes the further development of an integrated spatial and tabular relational database environment for GCMRC. To this end, Project K will continue to incorporate much of the relational database work in support of other science projects defined in this work plan. By building the expertise and capacity in data management, data acquisition, and relational database administration within one group, this project is better aligned to provide more comprehensive support to resource-specific science efforts and to the larger GCDAMP community.
Project Element K.3. Data Telemetry and Field Engineering (Ongoing Study)
Provides electrical engineering, programming and cloud data ingest services to enable systems ranging from basic power supply to sole data loggers to complex sensor-to-cloud real time data networks and ensure all systems are operating consistently and safely.
Project L: Overflight Remote Sensing in Support of GCDAMP and LTEMP
This project uses remote sensing to monitor the entirety of the terrestrial, riparian, and fluvial ecosystems along the Colorado River from the forebay of Glen Canyon Dam to Lake Mead at Pearce Ferry that are affected by the operation of Glen Canyon Dam. We analyze, interpret, and acquire overflight remote sensing data at a frequency commensurate with significant ecosystem changes along the river, including major tributaries.
Project Element L.1. Analysis and Interpretation of Overflight Remote Sensing Data (Partially Funded; Modified Study)
Produce and publish CRe landcover classification maps derived from analysis of the recently published the orthomosaic of high-resolution multispectral imagery acquired during the 2021 overflight.
Project M: Leadership, Management, and Support
Includes salaries, travel, and operating expenses for the management and operation of Grand Canyon Monitoring and Research Center (GCMRC). For U.S. Geological Survey (USGS) information product release and program administration, M.1 includes partial salaries for the following support staff: Budget Analyst (75%), Public Affairs Specialist (50%), Information Product Data System/Archive Technician (50%), and a Science Data Coordinator (50%). Leadership and management personnel salaries include those for the GCMRC Chief and Deputy Chief. Partial salary for one investigator is included for Tribal coordination and special projects. Project Element M.1 also covers GCMRC travel and training costs ($16,000 annually), including travel to support activities related to the Glen Canyon Dam Adaptive Management Program. GCMRC operating expenses include General Services Administration (GSA) vehicle costs (e.g., monthly lease fees, mileage costs, and costs for accidents and damage; $69,000 annually) and DOI vehicle costs (e.g., fuel, maintenance, supplies, and replacement costs; $45,000 annually). An annual contribution ($25,000) to the GCMRC equipment and vehicles working capital fund is currently unfunded.
Project N: Native Fish Population Dynamics (New Project)
Complete analysis of (primarily) existing data to understand basic demographic rates, assist managers in decision-making related to “Other Native Fishes” (ONF) conservation, and understand movements and sources of mortality of endangered razorback sucker (Xyrauchen texanus) released into the CRe to inform future augmentation strategies.
Project Element N.1. Sucker and Dace Distribution and Demographic Modeling (New Study; Partially Funded)
This project element involves 1) using existing data to estimate the probability of occurrence (occupancy) of all ONF to support the evaluation of trends in LTEMP metrics in development, 2) a synthesis of environmental and mark-recapture data to estimate demographic rates of bluehead and flannelmouth suckers throughout the CRe, and 3) assist NPS and USFWS in estimating growth and survival of razorback sucker released in Grand Canyon as part of a pilot-level augmentation study (2023-2025). Finally, 4) we plan to collaboratively investigate drivers of early life stage dynamics of ONF using larval and small-bodied fish data (2014-present, ASIR, Inc., and BIO-WEST, Inc.) collected in cooperation with the Bureau of Reclamation.
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Project Element B.3. Control Network and Survey Support (Ongoing Study; Unfunded)
The purposes of this project element are to establish and maintain the framework for high-accuracy change detection. This project element ensures that geospatial data collected across all projects of the program are accurately referenced, precisely defined, and can be reliably compared with past and future datasets. This project has been included as an element in Project B for the past several work plan cycles because much of the work in expanding the control network was done in cooperation with other Project B elements. Because this expansion of the control network is largely complete and future work will focus on maintenance of the network, documentation, and database management, we are considering migrating this project element to the Geospatial Science Project (Project K) in future work plans.
Project Element B.4. Streamflow, Sediment, and Sandbar Modeling (Ongoing Study; Unfunded)
The purposes of this project element are to 1) maintain and continue development of the existing sand routing model and sandbar response models, 2) begin development of a new streamflow model for the Colorado River between RM 30 and RM 61, and 3) continue development of a new fine-sediment (silt and clay) routing model. These models will be valuable in identifying and analyzing optimal management actions for sediment resources as part of the LTEMP ten-year review.
Research Question C.1.2. Can Bird Habitat Quality be Reliably Assessed by Combining Plant Traits with Estimates of Plant Species Composition and Cover? Can the Data Collected by the Riparian Plant Monitoring Program be used to Assess Patterns in Riparian-dependent Bird Communities? (unfunded)
Maintaining wildlife habitat is explicitly stated in Goal 11, but evaluating wildlife habitat quality requires different vegetation assessments than are needed for determining the diversity and productivity of native plant species. A method for evaluating vegetation as wildlife habitat is needed if this part of the goal is to be assessed. Birds and bird habitat are of interest to Navajo stakeholders (Martin, 2009), is a primary consideration in other southwestern riparian areas (Grand and others, 2024), and has been assessed previously in the CRe (Holmes and others, 2005b).
Research Question C.3.2. What are the Flow Scenarios Necessary to Achieve Specific Vegetation Objectives? (Unfunded)
This research question will conduct forward-looking modeling efforts to identify the flow conditions that would optimize the vegetation objectives listed in Goal 11. The metrics identified for Goal 11 will be used to frame the outcomes of this modeling (native dominance, richness, cover), similar to those used in Yackulic and others (2024). To date, our modeling efforts in the CRe have focused on the responses of riparian vegetation to flow patterns designed for other resources (Butterfield and others, 2023; Yackulic and others, 2024). While important, this approach does not provide a systematic assessment of how vegetation metrics respond to the full range of flow scenarios that could be implemented. Modeling a wider range of flow scenarios will provide a more comprehensive picture of the tradeoffs and compatibilities among different vegetation metrics and may also identify dam operations that can satisfy multiple objectives.
Research Question C.4.2. How Effective are Individual Plant Species at Altering Hydraulics and Sediment Transport? (Partially Funded)
The goal of Project Element C.4.2 is to incorporate physical plant traits into a 2-dimensional hydraulic model developed as part of Project Element B.4 to evaluate the effectiveness of different plant species in causing changes to the channel and floodplain. Plants are effective at causing channel/floodplain change because they affect flow velocities, shear stress, and sediment transport. However, Project Element B.4 is currently unfunded, and the hydraulic model will not be developed as part of the FY 2025–27 TWP. Therefore, as part of C.4.2, we will focus on collecting the relevant plant-trait data needed to determine the effects of plants on hydraulics and sediment transport at the plant and patch scale. These data will later be incorporated into the hydraulic model once it is developed to understand the effects of plants over large spatial scales. Collection of the necessary plant trait data will also benefit other aspects of Project C, particularly C.1.2, and be added to the GCMRC plant trait matrix (Palmquist and others, 2017) for future trait-based analyses of plant communities.
Project Element D.4. Pilot Study to Evaluate Potential to Extract Cultural and Ecological Information from Colorado River Deposits using eDNA, Phytoliths, and Pollen (New Study; Unfunded)
In FY 2025-26, we propose to collaborate with the NPS and interested Tribes to undertake a pilot study to examine the types of environmental information that potentially can be extracted from pre-dam sedimentary deposits, with a focus on extracting ancient eDNA for the purpose of characterizing the prehistoric vegetation community and cultural landscape at various points in the past. In addition, we intend to use this pilot study to determine whether eDNA can be used to document the presence of ancient horticulture fields and identify specific cultigens that were grown in the river corridor in the past.
Project Element D.5. Monitoring Petroglyphs and Pictographs with Photogrammetry and Lidar (New Study; Unfunded)
Like Project Element D.1, this work uses ground-based lidar but collects measurements at a finer resolution allowing for mm-scale characterization of the panel (Figure 7). Additionally, we use a Digital Single Lens Reflex (DSLR) camera to develop a true photogrammetric surface model (Figure 7) using Agisoft’s Metashape software. There are numerous sites and structural remains for which these monitoring procedures could be applied throughout the Colorado River corridor.
Project Element E.1. Phosphorus Budgeting in the Colorado River (Ongoing Study; Partially Funded)
An unfunded component of this project examines the hypothesis that benthic algae downstream of Lees Ferry sustain elevated GPP during the monsoon season in part through a nutrient acquisition strategy known as “overplus P uptake” (Harold, 1966; e.g., Lapointe and others, 2024), in which algal cells adapted to low-P environments opportunistically uptake extra P during storm events and store it for later use when baseline low-P conditions resume. This information could inform how we represent time lag effects after storms in canyon-wide GPP models.
Project Element E.2. Rates and Composition of Primary Producers in the Colorado River (Modified Study; Partially Funded)
The unfunded vegetation mapping project would provide a machine learning model that could be used to classify images and produce maps of submerged aquatic vegetation in Lees Ferry. Such maps could serve as a baseline to answer questions related to the effects of dam operations and reservoir conditions on dominant primary producers that fuel the “green” food web consumed by aquatic invertebrates and fishes.
Project Element E.3. Understanding the Energetic Basis of the Food Web in Western Grand Canyon (New Study; Unfunded)
This project element aims to understand controls on the base of the food web in Western Grand Canyon. We propose to quantify rates and drivers of decomposition, substrate-scale respiration, and whole-ecosystem primary production and ecosystem respiration in the Western Grand Canyon by deploying a miniDOT (PME) logger for metabolism estimates and, to the extent that outside funding continues, leveraging a new gaging station near Columbine. While turbulent whitewater conditions preclude estimation of respiration rates in most of Grand Canyon, we expect the lower gradient reach approaching Pearce Ferry to support paired estimates of GPP and ecosystem respiration. We also propose targeted decomposition experiments on natural litter and cotton strip assays to understand controls on detritivore vs. microbe-driven decomposition and how changes in temperature, nutrient availability, and litter quality may influence food availability for higher trophic levels. By pairing integrative estimates of ecosystem metabolism with finer-scale decomposition and respiration measurements, our approach will offer a uniquely holistic perspective on the energetic pathways underpinning food webs in Western Grand Canyon.
Project Element F.1. Aquatic Invertebrate Monitoring in Marble and Grand Canyons (Modified Study; Partially Funded)
To reduce costs, we propose to discontinue bat monitoring via both community science and at fixed stations throughout Glen and Grand Canyon (Kennedy and others 2024). Community science bat monitoring started in 2017 and is done in conjunction with community science light trapping of aquatic insects. Additionally, we propose to discontinue monitoring of invertebrate drift on annual spring river trips.
Project Element F.2. Aquatic Invertebrate Monitoring in Glen Canyon (Modified Study; Partially Funded)
We propose to discontinue monthly sticky trap (Smith and others 2014) and light trap sampling of adult aquatic insects in Glen Canyon.
Project Element G.5. Monitoring Humpback Chub Aggregation Relative Abundance and Distribution (Ongoing Study; Partially Funded)
Project Element G.5 funds an additional boat that can be used to seine backwaters to monitor juvenile humpback chub and warm-water nonnatives (funded in FY 2025 and FY 2026, not funded in FY 2027). One partial trip (launching at Diamond Creek and taking out at Pearce Ferry) was requested in FY 2026 but remains unfunded.
Project Element G.6. Juvenile Humpback Chub Monitoring – West (Ongoing Study; Unfunded)
Humpback chub in western Grand Canyon have increased dramatically in the last 5-10 years (Van Haverbeke and others, 2017) and JCM-west monitoring was established to determine how survival, growth, abundance, and recruitment differs for this relatively ‘new’ group compared to the more established group of LCR-spawning humpback chub. Understanding the drivers of this population was a goal identified in the Conservation Measures of the Biological Opinion. Furthermore, the 2016 fisheries PEP specifically recommended additional study in the lower part of the CRe. To address these goals, monitoring of the JCM-west reach (i.e., in Fall Canyon, located 210.5-214.0 river miles downstream of Lees Ferry) commenced in fall 2017 and continued through 2024.
Project Element G.7. Chute Falls Translocations (Ongoing Study; Unfunded)
Translocation and monitoring of humpback chub upstream of Chute Falls has been in place as a conservation action in Biological Opinions since 2002 (U.S. Fish and Wildlife Service, 2016, 2002). To date, over 4500 juvenile humpback chub have been translocated upstream of Chute Falls. Models suggest that humpback chub translocated above Chute Falls experience fast growth and high survival and that Chute Falls translocations are a beneficial (but limited) management tool for increasing abundance of humpback chub that can be used instead of nonnative removals in certain situations (Yackulic and others, 2021; Figure 12). In recent years (i.e., 2019, 2022) biologists have documented numerous unmarked subadult humpback chub, indicating that humpback chub may be spawning and recruiting above Chute Falls, potentially increasing the benefit of this management action.
Project Element G.8. Sampling of Springs in the Upper LCR (New Study; Unfunded)
Conduct two 5-day trips to the upper LCR in FY 2025 (1 in spring, 1 in fall) to evaluate the spatial distribution of humpback chub and other fishes in the intermittent flow habitats of the upper LCR. Collect eDNA samples to supplement physical capture data.
Project Element H.1. Rainbow Trout Fishery Monitoring in Glen Canyon (Modified Study)
Data collected under this element will be used to calculate metrics on the angling experience for both boat and walk-in anglers, including relative angler use, angler catch per unit effort values, and a rating of the fishery. AGFD angler surveys also provide information for Project J. For the FY 2025-27 work plan we propose to combine staffing resources and electrofishing-based monitoring trips between H.1 and H.2 to enable more precise and sensitive mark-recapture monitoring. In total (including H.1 and H.2), trout monitoring trips will be reduced from 8 to 4, compared to the previous work plan. Despite these changes, CPUE will continue to be calculated from data collected during the remaining 4 mark-recapture-focused trips.
Project Element I.1. System-wide Native Fishes and Nonnative Aquatic Species Monitoring (Ongoing Study)
The objective of this project element is to provide long-term data on the longitudinal distribution and status of the fish assemblage in the mainstem Colorado River from Lees Ferry (RM 0) to Pierce Ferry Rapid (RM 281). Nonnative fish surveillance that was conducted in the Lees Ferry reach during previous AGFD trout monitoring trips will be discontinued during this work plan due to adequate coverage from other agencies sampling the slough at RM -12 and other hot spots, by the dam, and other fixed and random sites throughout the Lees Ferry reach.
I.3.1. What High-Risk Species in Lake Powell are Moving into the Colorado River Undetected by Traditional Sampling Techniques? (Unfunded)
In the FY 2025-27 TWP, we propose to use automatic sampling technology to collect water samples to screen for emerging threats to the CRe. This will include use of an eDNA Autosampler (Smith Root; https://www.smith-root.com/services/training/environmental-dna-field-sampling-techniques) to automate sample collection in the field, which will allow us to ‘catch’ aquatic nonnative species year-round every few days even when trips are not on the water. The autosampler will be deployed in an area known to be a hot spot for nonnative species (e.g., downstream from dam, in slough) and/or within the draft tubes of the penstocks, and samples will be retrieved every two to four weeks.
I.3.2. How Comparable are eDNA Methods to Traditional Sampling Gear for Detecting Sources and Dispersal of Nonnative Fishes in the Colorado River? (Partially Funded)
Seining pools in the upper Little Colorado River drainage (Unfunded): Project Element G.8 monitors spring-fed pools in Piute Canyon in the upper LCR drainage to understand the extent to which humpback chub utilize these pools (and under what hydrologic conditions), as well as identify sources of nonnative species that could be flushed downstream into the LCR during monsoon season. Detection of very high or high-risk nonnative fishes could lead to Tribal management efforts. We plan on collecting three replicate eDNA samples from each paired LCR pool site in FY 2025 in collaboration with seining in Project Element G.8.
I.3.3. How do the Biophysical Characteristics of Lake Powell Affect the Likelihood of Nonnative Fish Entrainment through Glen Canyon Dam? (Unfunded)
In the FY 2025-27 TWP, we propose to build off this previously funded work by collecting eDNA samples in parcels of water at depth in the Forebay with a Van Dorn sampler, which is used for Lake Powell water quality monitoring and is designed to take samples in lakes and stratified water bodies. We hypothesize that forage fishes and their predators (e.g., smallmouth bass) may descend into deeper depths early in the morning as they follow their food source deeper into the reservoir, potentially leading to higher levels of entrainment at different times of the day.
I.3.4: What is the Incidence of Parasite Infestation in Humpback Chub in the Little Colorado River and Mainstem Colorado River? Can a Molecular Assay be Developed to Reduce Handling Time and Expand the Scope of Monitoring? (Unfunded)
We propose to collaborate with Oregon State University (Dave Lytle and Justin Sanders labs) to develop molecular assays for Asian tapeworm and Lernaea, which could eventually replace current detection methods.
Project Element J.3. Tribal Resources Research (Unfunded)
Focuses on developing more explicit pathways for recognition and meaningful consideration in the GCDAMP of the values and importance of Tribal resources, and the effects of management on these values. Building understanding within the GCDAMP of diverse forms of knowledge that convey plural values linked to ecosystems and resources, and piloting an ecosystem services-based approach to identify and integrate available Tribal benefits knowledge. We consider how the Cultural Benefits Learning Framework (CBLF) developed by Hoelting and others (2023) can intersect with Tribal research frameworks to increase recognition and integration of diverse knowledge forms that effectively convey the importance of Tribal resources.
Project Element L.2. Acquisition of Overflight Remote Sensing Imagery (New Study; Unfunded)
During FY 2026, GCMRC will implement a remote sensing overflight to collect high-resolution digital, multispectral imagery and topography of the CRe between Glen Canyon Dam and Lake Mead.
Project Element L.3. Acquisition of Airborne Lidar in Conjunction with Overflight Remote Sensing Imagery (New Study; Unfunded)
During the overflight proposed in Project Element L.2, GCMRC proposes to also acquire Quality Level 1 (QLI) or higher resolution airborne lidar data of the CRe.
Project M: Leadership, Management, and Support
An annual contribution ($25,000) to the GCMRC equipment and vehicles working capital fund is currently unfunded.
Project Element N.2. Predictive Modeling and Decision Support for Native Fishes (New Study; Unfunded)
We will use the results of demographic modeling in Project Element N.1 to develop predictive models to inform management and decision-making for ONF (e.g., matrix-based models, metapopulation viability model; Runge and others, 2018; Healy and others, 2023). Management decisions may include where and how to focus ONF restoration, augmentation (razorback sucker), or translocation efforts, how to protect native fish populations (e.g., in tributary refuges above barriers), prioritization of uncertain threats including nonnative species, or those related to LTEMP flow actions, among others.
Project Element N.3. Evaluating Dispersal and Sources of Mortality of Razorback Sucker using New Technology (New Study; Unfunded)
We propose to use acoustic telemetry to quantify dispersal from release sites and predation as a source of mortality of age-1 razorback sucker released in the CRe.
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