Glen Canyon Research Articles

Temporal Patterns of Fish Occurrence in the Colorado River, Grand Canyon in Response to Temperature, Largescale Drought, and Newly Exposed Habitat

ABSTRACTTwo large dams on the Colorado River, Glen Canyon and Hoover Dam, have profoundly altered the river within Grand Canyon. Owing to widespread drought and increased water usage throughout the Southwest, water levels in Lake Mead declined by over 40 m since 2000, exposing over 80 km of newly emerged riverine habitat in the western Grand Canyon that experiences higher water temperatures and increased turbidity relative to upstream portions of the Colorado River within the Grand Canyon. Our objective was to investigate how the probability of fish occurrence has changed within the Colorado River in Grand Canyon as abiotic conditions have shifted in relation to these altered environmental conditions. We used 22 years of long‐term fish monitoring data, from 2000 to 2022, on the mainstem of the Colorado River in the Grand Canyon to map the probability of occurrence based upon modeled water temperature for native and common nonnative salmonid species through space (river kilometer) and time in relation to declining water levels in Lake Mead. Our results suggest that native fish occurrence is strongly correlated with longitudinally increasing water temperature, while nonnative trout species were negatively correlated with increased water temperature downstream from the dam. Further, we found that nonnative trout species have experienced decreases in their probability of occurrence through time, while natives have experienced an increase in probability of occurrence. Information on distribution of fish prior to reservoir declines, and how the fish assemblage has shifted coincident with environmental changes, can help inform future management of native and nonnative fish in highly regulated river systems.

The Foundations of Glen Canyon Dam: Infrastructures of Dispossession on the Colorado Plateau

The Foundations of Glen Canyon Dam: Infrastructures of Dispossession on the Colorado Plateau

Review: The Foundations of Glen Canyon Dam: Infrastructures of Dispossession on the Colorado Plateau, by Erika Marie Bsumek

Review: <i>The Foundations of Glen Canyon Dam: Infrastructures of Dispossession on the Colorado Plateau</i>, by Erika Marie Bsumek

The John Wesley Powell Fossil Track Block—theropod tracks with ornithopod-like morphology from the Early Jurassic Navajo Sandstone, Glen Canyon National Recreation Area, Utah-Arizona

A large fallen block of Early Jurassic Navajo Sandstone located at Lake Powell, within Glen Canyon National Recreation Area, south-central Utah, displays natural casts of vertebrate tracks. The footprints occur on at least three track-bearing horizons preserved on and between stromatolitic sandstone beds. Two large, parallel trackways, plus a third, divergent trackway, on the main track layer (MTL) superficially resemble ornithopod footprints; however, they were produced by large-sized theropod dinosaurs, ratherthan ornithischians, and we identify these as Eubrontes. Small coelophysoid theropod tracks (Grallator) are the most common vertebrate ichnofossils on all track-bearing horizons, with approximately 50 footprints preserved on the MTL, six on the highest surface, and three on thinner float slabs stratigraphically lower in section. An additional 12 tracks in three trackways of Anchisauripus size occur on the MTL, but they superficially resemble Kayentapus in having wider divarication angles than typical Anchisauripus. The MTL also preserves at least five closely associated tetradactyl footprints that we identify as cf. Brasilichnium. A nearby, smaller fallen block preserves distinct Batrachopus tracks, which are rare in eolian environments. The microbial (possibly endoevaporitic) mats and stromatolitic horizons on which the animals had walked produced a distinct ichnomorphologic variation because of substrate consistency and the elastic properties of the mats, resulting in differential compaction of the bedding surfaces. Lithic compaction of the finer-grained sediments between denser, more resistant sandstone beds pre- and/or post-lithification resulted in additional deformation of the tracks, followed by natural erosion. We interpret these natural cast footprints on the MTL as possible transmitted tracks. The track-bearing, microbial-mat surfaces represent interdunal pooling of water, probably during periods of increased precipitation and/or rising water tables during wet seasons.

A Watershed Moment for Western U.S. Dams

AbstractThe summer of 2023 is a notable time for water‐resource management in the western United States: Glen Canyon Dam, on the Colorado River, turns 60 years old while the largest dam‐removal project in history is beginning on the Klamath River. This commentary discusses these events in the context of a changing paradigm for dam and reservoir management in this region. Since the era of large dam building began to wane six decades ago, new challenges have arisen for dam and reservoir management owing to climate change, population increase, reservoir sedimentation, declining safety of aging dams, and more environmentally focused management objectives. Today we also better understand dams' benefits, costs, and environmental impacts, including some that were unforeseen and took decades to become apparent. Where dams have become unsafe, obsolete (e.g., due to excessive reservoir sedimentation), and uneconomical beyond saving, dam removal has become common. The science and practice of dam removal are accelerating rapidly, and some long‐term physical and biological response studies are now available. Removal of four hydroelectric dams on the Klamath River will be a larger and more complex project than any previous dam removal. The imminency of this project reflects a very different situation for dam and reservoir management than 60 years ago. Looking forward, dam and reservoir management in the western United States and worldwide will require continued collaboration and innovative thinking to meet a wide range of objectives and to manage water resources sustainably for future generations.

The Colorado River water crisis: Its origin and the future

AbstractDuring much of the 21st century, natural runoff in the Colorado River basin has declined, while consumption has remained relatively constant, leading to historically low reservoir storage. Between January 2000 and April 2023, the amount of water stored in Lake Mead and Lake Powell, the two largest reservoirs in the United States, declined by 33.5 million acre feet (41.3 billion cubic meters). As of April 2023, total basin‐wide storage was sufficient to support the 21st century average rate of basin‐wide consumption for only 15 months. Runoff in spring 2023 is predicted to be large, providing a short‐term reprieve. However, it will take four to five additional unusually wet years in succession to refill Lake Powell and Lake Mead if basin‐wide water use remains unchanged. Increasing evapotranspiration and dry soils associated with global climate change makes such a scenario unlikely. To stabilize reservoir storage, basin‐wide use needs to equal modern runoff. To recover reservoir storage, basin‐wide use needs to decline even more. Based on 21st century average runoff, a 13%–20% decline in basin‐wide use would allow for stabilization and some reservoir storage recovery. Future policy debate about reservoir operations will inevitably concern whether most, or all, reservoir storage should be in Lake Mead or in Lake Powell. The choice of one or the other will result in significantly different environmental and recreational outcomes for Glen Canyon and the Grand Canyon.This article is categorized under: Water and Life &gt; Stresses and Pressures on Ecosystems Human Water &gt; Water Governance Science of Water &gt; Water and Environmental Change

Archaeological sites in Grand Canyon National Park along the Colorado River are eroding owing to six decades of Glen Canyon Dam operations

The archaeological record documenting human history in deserts is commonly concentrated along rivers in terraces or other landforms built by river sediment deposits. Today that record is at risk in many river valleys owing to human resource and infrastructure development activities, including the construction and operation of dams. We assessed the effects of the operations of Glen Canyon Dam – which, since its closure in 1963, has imposed drastic changes to flow, sediment supply and distribution, and riparian vegetation – on a population of 362 archaeological sites in the Colorado River corridor through Grand Canyon National Park, Arizona, USA. We leverage 50 years of evidence from aerial photographs and more than 30 years of field observations and measurements of archaeological-site topography and wind patterns to evaluate changes in the physical integrity of archaeological sites using two geomorphology-based site classification systems. We find that most archaeological sites are eroding; moreover, most are at increased risk of continuing to erode, due to six decades of operations of Glen Canyon Dam. Results show that the wind-driven (aeolian) supply of river-sourced sand, essential for covering archaeological sites and protecting them from erosion, has decreased for most sites since 1973 owing to effects of long-term dam operations on river sediment supply and riparian vegetation expansion on sandbars. Results show that the proportion of sites affected by erosion from gullies controlled by the local base-level of the Colorado River has increased since 2000. These changes to landscape processes affecting archaeological site integrity limit the ability of the National Park Service and Grand Canyon-affiliated Native American Tribes to achieve environmental management goals to maintain or improve site integrity in situ. We identify three environmental management opportunities that could be used to a greater extent to decrease the risk of erosion and increase the potential for in-situ preservation of archaeological sites. Environmental management opportunities are: 1) sediment-rich controlled river floods to increase the aeolian supply of river-sourced sand, 2) extended periods of low river flow to increase the aeolian supply of river-sourced sand, 3) the removal of riparian vegetation barriers to the aeolian transport of river-sourced sand.

A Glimpse Through Time: Preliminary Report of the Andre’s Alcove Tracksite, Lower Jurassic Navajo Sandstone, Glen Canyon National Recreation Area, Utah

In November 2018, a team of researchers from the National Park Service and the St. George Dinosaur Discovery Site documented fossil vertebrate tracks at the Andre’s Alcove Tracksite (AAT) in the Lower Jurassic (?190–185 Ma) Navajo Sandstone in Glen Canyon National Recreation Area, Utah. The tracks at the AAT were photo-documented for photogrammetric processing using Agisoft Photoscan Professional to enable the track surface to be studied remotely. Ichnotaxa already identified at the AAT include those of small ornithischian dinosaurs (Anomoepus), theropod dinosaurs (Grallator, Eubrontes), and protosuchian crocodylomorphs (Batrachopus). Vertebrate body fossils are rarer in the Navajo Sandstone than in underlying, earlier Jurassic strata; the AAT site therefore provides important insights into late Early Jurassic vertebrate diversity and behaviors at the onset of the Navajo Erg in the American Southwest.

Wear the Blue Star: Frontier Values vs. Environmentalism in News Coverage of Colorado River Dams, 1954-1956

ABSTRACT This study examines news coverage of a federal project that resulted in the building of Glen Canyon Dam on the Colorado River and sparked an environmental controversy. The project pitted boosters against conservationists, and this research illustrates how western newspapers promoted growth through dams and irrigation. Acknowledging the region in which several newspapers operated, this study uses New Western History to better understand journalism history by highlighting the harsh landscape and the persistence of pioneer values in the 1950s. This research also introduces a new element of environmental journalism history by adding to understanding of such reporting in the 1950s and by approaching the dam controversy from the perspective of journalism rather than environmentalism. Whether newspapers focused on growth and prosperity or preserving natural beauty, their coverage reflected the complexity of the region and its ecosystem.

Declines in prey production during the collapse of a tailwater Rainbow Trout population are associated with changing reservoir conditions

AbstractObjectiveUnderstanding how energy moves through food webs and limits productivity at various trophic levels is a central question in aquatic ecology and can provide insight into drivers of fish population dynamics since many fish populations are food limited. In this study, we seek to better understand what factors drove a decline of &gt;85% in the number of Rainbow TroutOncorhynchus mykiss found in the tailwater portion of the Colorado River below Glen Canyon Dam during 2012–2016.MethodsWe estimate the production of dominant prey using data from previously published studies of Rainbow Trout abundance and growth alongside drift and diet samples. We test how prey production correlates to both proximate (e.g., nutrients) and distal (e.g., limnological conditions in the upriver reservoir) drivers.ResultResults suggest that gross consumption of invertebrate prey by the Rainbow Trout population declined from an annual mean of 423 to 69 kg/d. Daily production rates of dominant prey in aggregate declined from a high of 0.173 to 0.018 g·m−2·d−1. Chironomids accounted for 70% of the decline in prey production. Foraging efficiency by Rainbow Trout (range, 0.99–0.67) was high across the range of prey production rates. After the Rainbow Trout population had declined by ~90%, prey consumption saturated at higher rates of prey production and the gross quantity of daily drift exported from the reach increased from 8.9 to 12.7 kg/d.ConclusionRainbow Trout population dynamics are largely influenced by changes in prey production, which is itself driven by soluble reactive phosphorus (SRP) concentrations in the reservoir. The SRP model predicted that prey production would increase by 32 kg/d (SE, 9) for each 1 μg/L increase in SRP. These concentrations were indirectly influenced by reservoir hydrology and biogeochemistry, linkages that may extend far beyond the confines of this tailwater fishery and into the downstream reaches of the Grand Canyon's Colorado River ecosystem.

Behind the Bears Ears: Exploring the Cultural and Natural Histories of a Sacred Landscape

Behind the Bears Ears: Exploring the Cultural and Natural Histories of a Sacred Landscape

Drought-related changes in water quality surpass effects of experimental flows on trout growth downstream of Lake Powell reservoir

Flows released from reservoirs are often modified to mitigate the negative ecosystem effects of dams. We estimated the effects of two experimental flows, fall-timed floods and elimination of sub-daily variation in flows on weekends, on growth rates of rainbow trout ( Oncorhynchus mykiss) in the Colorado River downstream from Glen Canyon Dam. Experimental flow effects were compared to effects of water temperature, phosphorous concentration, solar insolation, and competition, by fitting mixed effect von Bertalanffy models to ∼ 10 000 observations of growth from mark-recapture between 2012 and 2021. There was strong support for models predicting faster growth during intervals with higher solar insolation, and lower water temperature and competition for prey. Effects of phosphorus and experimental flows were small and uncertain. Drought-related increases in dam release temperatures during summer and fall were predicted to result in severe weight loss for larger trout and could eventually threaten the viability of the population and the fishery it supports. The effects of water temperature and competition on fish growth substantially exceeded the effects of controlled floods and steadier flows.

Featured Collection Introduction: Severe Sustained Drought Revisited: Managing the Colorado River System in Times of Water Shortage 25 Years Later — Part I

Featured Collection Introduction: Severe Sustained Drought Revisited: Managing the Colorado River System in Times of Water Shortage 25 Years Later — Part I

Experimental reductions in subdaily flow fluctuations increased gross primary productivity for 425 river kilometers downstream.

Aquatic primary production is the foundation of many river food webs. Dams change the physical template of rivers, often driving food webs toward greater reliance on aquatic primary production. Nonetheless, the effects of regulated flow regimes on primary production are poorly understood. Load following is a common dam flow management strategy that involves subdaily changes in water releases proportional to fluctuations in electrical power demand. This flow regime causes an artificial tide, wetting and drying channel margins and altering river depth and water clarity, all processes that are likely to affect primary production. In collaboration with dam operators, we designed an experimental flow regime whose goal was to mitigate negative effects of load following on ecosystem processes. The experimental flow contrasted steady-low flows on weekends with load following flows on weekdays. Here, we quantify the effect of this experimental flow on springtime gross primary production (GPP) 90-to-425km downstream of Glen Canyon Dam on the Colorado River, AZ, USA. GPP during steady-low flows was 41% higher than during load following flows, mostly owing to nonlinear reductions in sediment-driven turbidity. The experimental flow increased weekly GPP even after controlling for variation in weekly mean discharge, demonstrating a negative effect of load following on GPP. We estimate that this environmental flow increased springtime carbon fixation by 0.27g C m-2 d-1, which is ecologically meaningful considering median C fixation in 356US rivers of 0.44g C m-2 d-1 and the fact that native fish populations in this river are food-limited.

Integrative Biodiversity Inventories: Characterizing Lichen-Forming Fungal Diversity in Glen Canyon National Recreation Area Using DNA Barcoding and Vouchered Specimens

El río Colorado y sus afluentes en la meseta de Colorado albergan ecosistemas fluviales desérticos únicos y condiciones ambientales cambiantes. Dentro de esta región, el Área Recreativa Nacional de Glen Canyon (GCNRA, por sus siglas en inglés) se compone de un terreno desértico irregular y elevado, el cual es administrado por el Servicio de Parques Nacionales de los Estados Unidos como área recreativa y de conservación. A pesar de la importancia ecológica y económica de GCNRA, varios componentes importantes de las comunidades ecológicas que allí se encuentran permanecen mal caracterizados, incluidos los líquenes. El caracterizar la diversidad precisa de los hongos formadores de líquenes representa un desafío debido a que se trata de grupos taxonómicos poco conocidos, regiones/hábitats escasamente explorados y diversas interpretaciones de las diferencias morfológicas, incluido el reconocimiento de formas modificadas por el medio ambiente. Para comprender mejor la diversidad de líquenes en GCNRA, utilizamos un enfoque taxonómico integrador, incorporando tanto la identificación tradicional basada en la morfología como la información del marcador de código de barras de ADN de hongos estándar (marcador ITS), para compilar un inventario completo de hongos formadores de líquenes en Fifty-Mile Canyon. En 2019 se recolectaron especímenes de liquen, y de estos se secuenció el marcador ITS. Los linajes candidatos a nivel de especie se delimitaron a partir de alineaciones de secuencias múltiples a nivel de familia, utilizando el servidor web Assemble Species by Automatic Partitioning. Posteriormente, se evaluó los especímenes que comprenden especies candidatas basadas en el ADN, utilizando cuando fue posible, caracteres tradicionales de diagnóstico taxonómico para vincularlos con las especies descritas actualmente. En Fifty-Mile Canyon, documentamos 100 especies putativas de 15 familias, cada una representada por especímenes certificados, datos de secuencia de ITS y documentación fotográfica. A modo de comparación, un muestreo de registros históricos de GCNRA reveló un total de 124 especies de hongos formadores de líquenes, documentadas en toda la NRA y las tierras adyacentes. Aproximadamente el 50% de las especies documentadas en Fifty-Mile Canyon no se habían encontrado previamente en GCNRA, y proporciones similares de diversidad de especies se han encontrado en GCNRA, pero no se observaron en nuestro estudio. Registramos tres especies nuevas en Norteamérica: Calogaya ferrugineoides (H. Magn.) Arup, Frödén & Søchting, Endocarpon deserticola T. Zhang, X.L. Wei & J.C. Wei y Xanthocarpia ferrarii (Bagl.) Frödén, Arup & Søchting, verificadas usando datos de secuencia de ITS. Además, describimos formalmente a Circinaria squamulosa sp. nov., actualmente sólo conocido en losas de arenisca en Fifty-Mile Canyon. Sin embargo, la identidad taxonómica de muchas de las especies candidatas de Fifty-Mile Canyon permaneció ambigua a nivel de especie, y algunas colecciones probablemente representan linajes a nivel de especie no descritos. Nuestros resultados revelaron una gran e inesperada diversidad a nivel de especie de hongos formadores de líquenes a escala local y la diversidad general de líquenes en todo el GCNRA probablemente esté muy subestimada. Estos datos, incluidos los códigos de barras de ADN de la gran mayoría de los hongos formadores de líquenes que se encuentran en este cañón, proporcionan un recurso importante que puede integrarse en investigaciones posteriores acerca de la biodiversidad de líquenes en el suroeste de los Estados Unidos y otros climas semiáridos.

Population Reproductive Structure of Rainbow Trout Determined by Histology and Advancing Methods to Assign Sex and Assess Spawning Capability

AbstractRainbow TroutOncorhynchus mykisshave been intensively studied and gametogenesis has been described, but the use of reproductive indices in field studies has not been widely applied when assessing variability in growth or recruitment dynamics. We integrated descriptions for gametogenesis within the framework of standardized terminology for reproductive development in teleosts to develop sex‐specific criteria for assignment of reproductive phases. We used these descriptions and histological analysis of gonad tissue collected from Rainbow Trout in the Colorado River downstream from Glen Canyon Dam to quantify season‐, size‐, and sex‐specific variation in population reproductive structure. The accuracy of nonlethal methods (manual expression and ultrasonography) was evaluated for assigning sex by comparing estimates with those determined by histology. Rainbow Trout were sampled through an annual spawning cycle from October 2018 to April 2019. Spawning capable males were available across the entire period, with a higher proportion earlier in the season compared to later. Females were spawning capable in October, with a peak in February; by April, they were in the early developing phase, indicating that spawning had ended. Elevated levels of atresia (19% for fall spawners) and evidence for delayed maturation were identified, suggesting energetic limitations on the reproductive potential of the population. For both sexes, the probability of being spawning capable increased with fork length, with minimum sizes of ≥283 mm for females and ≥187 mm for males. Sex assignment using ultrasonography was more accurate (46%) than manual expression of gametes (9%), as only a small proportion of males and females expressed gametes. Probabilities of correct sex assignment using ultrasonography were strongly influenced by reproductive phase, with spawning capable fish (females: 100%; males: 77%) having significantly higher probabilities of correct sex assignment compared to immature fish. Furthermore, probabilities of correct sex assignment increased with fish size and were higher for females than for males. Results provide a framework for quantifying spawning capability and population reproductive structure in ongoing research to better understand the drivers of recruitment variability in aquatic ecosystems.

Sedimentary record of annual-decadal timescale reservoir dynamics: Anthropogenic stratigraphy of Lake Powell, Utah, U.S.A.

The tributaries of Lake Powell were impounded following construction of Glen Canyon Dam, resulting in deposition of reservoir sediment over a ∼650 km2 area since 1963. These units have been exposed through erosion as water storage in Lake Powell has decreased since 2000. This anthropogenic sedimentary record reflects the complex interplay among wet and dry periods of Colorado River runoff and the reservoir operating rules of Lake Powell. The relevant sedimentary exposures are mapped at reconnaissance level over 300 river-km above Glen Canyon Dam in canyons of the Colorado, San Juan, Escalante, and Dirty Devil Rivers. A detailed reference section measured in Calf Canyon, a tributary to the Colorado River, preserves more than 12 m of lacustrine, mainstem Colorado River, and local tributary sediment in an up-river location and elevation that is determined to have been inundated only during the highest reservoir level periods. At Calf Canyon, exposed reservoir sediment is comprised of cyclic sand-mud interbeds that record periods of deposition when reservoir level was at or above full pool. Six depositional cycles are identified in Calf Canyon, and each of these is interpreted to represent rapid sand deposition during Colorado River flood events (likely related to spring snowmelt runoff) followed by deposition of lacustrine mud while reservoir levels were high. The lacustrine mud units display significant pedogenic modification, indicating exposure and colonization dominated by tamarisk plants, prior to deposition of the next sand unit. High-precision elevation surveys of the 6 main lacustrine marker beds in Calf Canyon are correlated to multiple lake level highstands between 1975 and 2000. Preliminary observations suggest that age-equivalent strata are widespread within the reservoir-affected zones of all major tributaries including the Colorado and San Juan River arms as well as the Escalante and Dirty Devil Rivers. We predict that future mapping in other Lake Powell side canyons will demonstrate strong local control on sediment provenance, dictated by side canyon lithology, as well as time-transgressive deposition (and erosion) moving up and down the main canyons.

Geologic Carbon Storage of Anthropogenic CO2 under the Colorado Plateau in Emery County, Utah

Geologic Carbon Storage (GCS) is a promising technology for storing large volumes of anthropogenic CO2 effectively and permanently. Numerical simulations are an integral part of site selection and characterization for any potential GCS site. As part of the DOE-funded CarbonSAFE Rocky Mountains Phase I project, a regional GCS analysis was undertaken to understand the efficacy of storing CO2 emissions from the power generation and heavy industry in central Utah’s favorable geology. In this study, the injection of CO2 for geologic storage was simulated in the Navajo Sandstone Formation in Emery County, Utah. Carbon dioxide was sourced from regional power generation stations and heavy industries throughout Utah, with an emphasis on emissions reduction at the Hunter Power Plant near Castle Dale, Utah. A simulation grid was extracted from the project’s geological model encompassing an area around Price, Huntington, and Castle Dale in central Utah. The Navajo Sandstone Member of the Glen Canyon Group was the target of CO2 injection with the overlying Carmel formation providing the primary seal. A suite of simulations was performed assessing the viability of this area for permanent CO2 storage. Results indicate that the area can not only store 46 million metric tons of anthropogenic CO2, meeting the project goals, but this area has the capacity to securely store at least 1.3 billion tons of CO2, suggesting the injection site and surrounding geology are suitable locations for commercial-scale GCS.

Maximum benefits for water resources and hydropower based on linear programming

With the increasingly serious development of greenhouse effect, hydropower, as a clean and environmentally friendly energy technology, is attracting more and more attention. On the Colorado River, the Glen Canyon Dam and the Hoover Dam simultaneously supplies water and electricity to Arizona (AZ), California (CA), Wyoming (WY), New Mexico (NM) and Colorado State (CO). However, nowadays, the two dams cannot coordinate with each other well to exert their effectiveness, and the water resources cannot be fully utilized, which makes us upset. At the same time, we also succeeded to find the solution, when there is not enough water to meet all hydropower needs [1.2]. We calculate the gap between water supply and electricity supply. Based on the Supply and demand models for water and hydropower, when there is not enough water, we deduced how much additional water needs to be injected into the dams could fill these gaps [3.4.5]. Besides, we analyzed how our model would respond, when many other supply and demand conditions changed.

Dynamic Flow Alteration Index for Complex River Networks With Cascading Reservoir Systems

AbstractLarge dams degrade the river’s health by heavily regulating the natural flows. Despite a long history of research on flow regulation due to dams, most studies focused only on the impact of a single dam and ignored the combined impact of flow regulation on a river network. We propose a new Dynamic Flow Alteration Index (DFAI) to quantify the local and cumulative degree of regulation by comparing the observed controlled flows with the naturalized flows based on a moving time horizon for the highly regulated Colorado River Basin. The proposed DFAI matches closely to dam’s localized regulation for headwater gages and starts to diverge as we move downstream due to increase in cumulative impact of the dams. DFAI considers the impact of dam operations on flow characteristics such as shifting of peak flow occurrence and dampening of peak flows. DFAI estimates the degree of regulation to be small for upstream dams and finds the maximum network regulation to be 2.52 years at Glen Canyon reservoir. DFAI also successfully captures the reduction in cumulative regulation when dam operations (e.g., Hoover Dam) bring the altered flow in synchronization with natural regime due to downstream flow requirements. The impact of San Juan River Basin Recovery Implementation Program is also captured by DFAI as the reduction in network regulation drops by 1.5 years for Navajo Dam. Our findings using DFAI suggest the need to develop naturalized flows for major river basins to quantify the flow alteration under continually changing climate and human influences.