Towards full predictions of temperature dynamics in McNary Dam forebay using OpenFOAM

Hydroelectric facilities impact water temperature; low velocities in a reservoir increase residence time and enhance heat exchange in surface layers. In this study, an unsteady three-dimensional model was developed to predict the temperatm＇e dynamics in the McNary Dam forebay. The model is based on the open-source code OpenFOAM. RANS equations with the Boussinesq approximation were used to solve the flow field. A： realizable k-ε model that accounts for the production of wind turbulence was developed. Solar radiation and convective heat transfer at the free surface were included. The result of the model was compared with the field data collected on August 18, 2004. Changes in diurnal stratification were adequately predicted by the model. Observed vertical and lateral temperature distributions were accurately captured. Results indicate that the model can be used as a numerical tool to assess structural and operational alternatives to reduce the forebay temperature.

Developing a Family of Curves for the HEC-18 Scour Equation

Accurate pier scour predictions are essential to the safe and efficient design of bridge crossings. Current practice uses empirical formulas largely derived from laboratory experiments to predict local scour depth around single-bridge piers. The resulting formulas are hindered by insufficient consideration of scaling effects and hydrodynamic forces. When applied to full-scale designs, these formula deficiencies lead to excessive over prediction of scour depths and increased construction costs. In an effort to improve the predictive capabilities of the HEC-18 scour model, this work uses field-scale data and nonlinear regression to develop a family of equations optimized for various non-cohesive soil conditions. Improving the predictive capabilities of well-accepted equations saves scarce project dollars without sacrificing safety. To help improve acceptance of modified equations, this work strives to maintain the familiar form of the HEC-18 equation. When compared to the HEC-18 local pier scour equation, this process reduced the mean square error of a validation data set while maintaining over prediction.

Pre- and Post-Construction Assessment of Nutrient Concentrations at Shallow Water Habitat Restoration Sites on the Lower Missouri River

Loss of shallow water habitat (SWH) is hypothesized as a factor contributing to the decline of native Missouri River fishes, including the endangered pallid sturgeon. As a result, the restoration of SWH is a high priority in this large river system. Restoration activities often include constructing side channel chutes;however, limited information exists on the potential negative, unintended effects of chute construction activities on water quality. This study was designed to better understand the possible effects of chute construction, both initially and as chute development continues, on Missouri River nutrient concentrations. Our first objective was to determine if the addition of sediment from proposed chute locations to river water samples (i.e., elutriate samples) increased nutrient concentrations relative to water-only river samples collected just upstream of the proposed chute locations or river water samples collected from eight long-term water quality monitoring stations. Our second objective was to determine if nutrient concentrations of river samples monitored during 2009 and 2010 increased after water passed through previously-constructed chutes. Nutrient concentrations of elutriate samples were not significantly higher than river water samples collected just upstream of the proposed chute locations;the same was true for Missouri River water samples collected from seven of eight long-term water quality monitoring stations. Furthermore, monitoring of nutrient concentrations collected from water samples at the outlet of previously-constructed chutes were not significantly higher than water samples collected at the upstream inlet of these chutes. Our results suggest that individual SWH chute construction projects designed to restore some of the natural form and function of the Missouri River are unlikely to significantly increase Missouri Rivernutrient concentrations initially or as these chutes continue to develop.

The Effects of Rearing Temperature on American Glass Eels

American eels are declining throughout their range requiring a better understanding of physiological requirements of all life stages and optimal conditions for laboratory rearing and aquaculture. American glass eels (Anguilla rostrata) were housed for 3 weeks at 14&degC, 18&degC, 22&degC, or 26&degC to determine optimal juvenile rearing temperature in the laboratory. All treatments exhibited weight gain over the course of the study except the 14&degC treatment;however, there were only marginal differences in final weight between the 18&degC and 14&degC treatments and no differences in length. Variation in length and weight generally increased as temperature increased with significant differences in the standard error of weight between 14&degC and the 22&degC and 26&degC treatments and between 18&degC and 26&degC. Mortality was significantly greater than expected by chance at 26&degC?(7 deaths) and no mortality was observed at 14&degC. Body condition (based on the residuals from the weight-length relationships), conversely, was lowest in the 14&degC treatment. Considering all response variables, optimal laboratory rearing conditions were observed between 18&degC - 22&degC. Within a week of experimentation, evidence of gas bubble disease was observed and by completion noted in all treatments except at 14&degC, likely as a function of decreased gas solubility at warmer temperatures. Levels of total gas pressure (103% - 108%) and Δp (28 - 54 mm Hg) values may account for the gas bubbles observed.

Analysis and O-D Demand Estimation of a Public Bike-Sharing Program in Las Vegas

Bike-share systems are an effective way of mitigating congestion on the road. In addition, bike-share systems have been built in universities to serve for trips to work/commuting as well as the trips on campus. In Las Vegas, a bike-share system was proposed at the University of Nevada, Las Vegas. This study analyzed factors that influence the usage of bike-share program and estimated the origin-destination demand. To achieve these objectives, first, a literature review was conducted on university bike-sharing systems in the U.S. and abroad. Then, a survey with a questionnaire was distributed to UNLV to obtain the users’ preferences to the locations of the proposed bike-share stations and their likelihood and frequency to use the bike-share program. In total, 241 faculty, staff, and students responded to the survey. About 50% of those participating in the survey expressed willingness to use the bike-share system for commuting and 60% said they are willing to use bike share for on-campus travel. Commuting and on-campus travel are two different types of travel, and the factors to determine whether an individual would use the bike-share system are quite different for each. It was estimated that there would be 3450 members for a bike-share program at UNLV, each making bicycle trips with varying frequencies, producing 1966 trips per day.

Determination of the Size of a Proposed Bike-Sharing Program in Las Vegas, Nevada

Bike-share systems have been installed in cities worldwide as a way to attract travelers to use transit rather than the automobile. This has been proved to be an effective way of mitigating congestion on the road. The objective of this study is to develop a method to determine the size of the bike-share program in terms of the number of bicycles, the number and location of the stations, the number of docks at each station. To achieve the objectives of this study, a literature review was conducted on university bike-sharing systems in the U.S. and abroad. Various cases of bike-share programs were analyzed, in which each case consisted of a different number and location of bike-share stations. The demand corresponding to these stations was used as the input to a simulation model developed in this study to determine the number of docks in stations and bicycles in the system on and around campus at UNLV. These sizing parameters of the bike-share system then were used in a cost and benefit analysis to determine which cases could achieve maximum benefit, given a limitation of the initial costs. It was found that provision of one peripheral station and three internal stations at strategic locations provide relatively higher benefit cost ratio at lower initial cost.

Decay of Pressure Fluctuation in the Hyporheic Zone around a Cylinder

Erosion around a submerged cylinder is a well-studied problem, and is of particular interest in bridge pier scour applications. Particles erode when lift and drag forces overcome a critical threshold. These forces are typically studied from above the water-riverbed interface and are related to geometry and surficial processes. The present study maps hyporheic pressure fluctuations as they are related to surface water velocity fluctuations. Relatively, high-pressure events in the subsurface promote a destabilizing force from within the riverbed and increase the potential for the mobilization of sediment. Differential pressure transducers were fitted within a vertical cylinder in a movable bed flume. The pressure ports were flush with the cylinder surface and below the water-sand interface. The three-orthogonal components of velocity were recorded synchronously with differential pressure measured over a 15 mm depth. As expected, results show decay in pressure fluctuations as a function of depth.

Nanofibers enabled advanced gas sensors:A review

The advancement of gas sensor technology over the past decades has led to remarkable progress and achievements in pollution control and environmental protection.Compared with other sensing materials,electrospun nanofibers have attracted significant attention,which is mainly due to their unique characteristics,including but not limited to high surface area,easy structure design,facile facility setup,multifunctional properties,etc.,making them outstanding candidates for potential applications in this field.This review provides an overview of the applications of electrospun nanofibers in gas sensors,concentrating on carbon monoxide,hydrogen,carbon dioxide,hydrogen sulfide,ammonia,nitrogen oxides,oxygen,and volatile organic compounds.It begins with a brief introduction to sensing materials and the advantages of electrospun nanofibers along with their ongoing research.The principles and progress of electrospinning are then discussed.Afterward,the corresponding properties of electrospun nanofibers in diverse gas sensors are thoroughly reviewed.Finally,a future vision regarding challenges and perspectives in this area is proposed.This review provides an extensive and comprehensive reference to utilize advanced electrospun nanofibers to generate novel sensors,facilitating their performance in high-demand areas.

G-WADI—the first decade

The G-WADI network by UNESCO promotes the global capacity for management of water resources in arid and semi-arid areas. The primary aim has been to build a comprehensive global network to promote regional and international cooperation so as to in- crease knowledge and improve management practices through the sharing of information. The G-WADI objectives and achieve- ments of the past 10 years are reviewed. A number of key initiatives have been implemented^the formation of five regional net- works, the creation of a central G-WADI web site, promotion of near-real-time rainfall distribution software enhanced by the in- clusion of satellite based precipitation estimations, as well as workshop and web-based activities on chemical and isotopic tracers and on rain water harvesting. Two workshops on surface and on groundwater modeling, supported by publications have been held in India and China. The Asian G-WADI network remains very active, but activities in the other three regions are developing （Af- rica, Arab Region, Latin America and the Caribbean）.

DETERMINING CONSTRUCTION DEBRIS RECYCLING DUMPSTER DENSITIES

Solid waste generated by construction and demolition(C&D)projects account for a significant portion of solid waste generated and landfilled in the United States.The United States Green Building Council’s(USGBC)Leadership in Energy and Environmental Design(LEED®)credit system encourages recycling of C&D debris.Data from a new construction project adhering to LEED®guidelines is used to investigate dumpster densities for construction debris.These are conversion factors from waste collection volumes to waste masses useful for verification of recycling credit goals,estimating waste management needs and optimizing waste management costs.The proper estimation of waste material dumpster density is important in order to combine sustainability with cost effectiveness.The field data was generated from a 9700 m2(104,000 ft2)building under construction in Columbia,South Carolina with a precast concrete and brick veneer.The categories of waste investigated were general trash,masonry,wood,steel,and sheetrock.It was found that there are significant differences in many of the conversion factors for this project as compared to factors from other waste material recycling databases.

Graph-theoretic algorithms for cyber-physical vulnerability analysis of power grid with incomplete information

A key focus recently has been on assessing therisk of a coordinated cyber-physical attack and minimizing the impact of a successful attack. Most of the cyberattackers will have limited system information and conventional power grid N-1 security analysis cannot be extended to assess the risk. Centrality measures are widely used in the network science and an attacker with incomplete information can use it to identify power system vulnerabilities by defining the system as a complex network but without real-time system measurements. This paper presents a graph theory based centrality indices for vulnerability assessment of the power system due to various bus and branch contingencies using limited system information and provides a preliminary defense mechanism to prevent such an attack. Proposed work answers the fundamental question of possible attack scenarios by balancing risk(limited information with low risk to get caught orhigh risk attack to access more system information) and impact(identifying contingencies with maximal impact on system operation). Statistical comparisons are made between the graph theory measures compared to the corresponding DC power flow based N-X linear sensitivity measures. A unified N-X centrality based performance index is proposed and validated against the AC power flow based performance index by doing the real-time simulations of an N-3 attack scenario. Defensive mechanisms using topology-based performance indices are also presented.

Anthropogenic impacts to the sediment budget of São Francisco River navigation channel using SWAT

The São Francisco River Basin,located in eastern Brazil,has undergone a significant amount of anthropogenic changes in the last several decades,such as agricultural expansion,irrigation activities,mining,and the construction of large dams.Together,these changes have altered the historic sediment budget and have led to an aggradation of sediments in the navigation channel,impacting the ability to efficiently ship agricultural commodities to regional ports.In an effort to aid decision makers in future waterway navigation planning,an international partnership between the Brazilian government agency CODEVASF and the US Army Corps of Engineers(USACE)was created.Through this partnership a SWAT model of the 630000 km2 São Francisco River basin was developed to better understand both the historic and current sediment budget within the navigation channel.The SWAT model of the São Francisco River Basin was calibrated for hydrology and sediment loads.Monthly discharges were calibrated at 17 Agência Nacional deÁguas(ANA)gages,with Nash-Sutcliffe efficiency(NSE)values ranging from 0.42 to 0.75 for an eleven year simulation.Sediment loads were calibrated to an ANA sediment gage located in the Middle São Francisco River Navigation Channel,with a PBIAS(Percent Bias)of 11.6.Based on model results,the aggradation rate of sediment in the São Francisco River and major tributaries has increased by approximately 20 Mt since Pre-European settlement of the basin(from approximately 7 Mt/a to 27 Mt/a).This increase has contributed to an impaired navigation channel due to shoaling of sandy sediments in the navigation channel.

Evaluation of stereology for snow microstructure measurement and microwave emission modeling:a case study

Reliablemicrostructuremeasurement of snow is a requirement for microwave radiative transfer model validation.Snow specific surface area(SSA)can be measured using stereological methods,in which snow samples are cast in the field and photographed in the laboratory.Processing stereology photographs manually by counting intersections of test cycloids with air-ice boundaries reduces the problems in binary segmentation.This paper is a case study to evaluate the repeatability of the manually stereology interpretation by two independent research groups.We further assessed how uncertainty in snow SSA influences simulated brightness temperature(TB)driven by the Microwave Emission Model of Layered Snowpacks(MEMLS),and how stereology compares to Near Infrared(NIR)camera and hand lens.Data was obtained from two alpine snow profiles from Steamboat Springs,Colorado.Results showed that stereological SSA values measured by two groups are highly consistent,and the ground radiometer measured T_(B)at 19 and 37 GHz was successfully predicted(RMSE<3.8 K);simulations using NIR SSA and hand-lens geometric grain size(Dg)measurements have larger errors.This conclusion was not sensitive to uncertainty in the free parameters of TB modeling.

Shorebird patches as fingerprints of fractal coastline fluctuations due to climate change

Introduction:The Florida coast is one of the most species-rich ecosystems in the world.This paper focuses on the sensitivity of the habitat of threatened and endangered shorebirds to sea level rise induced by climate change,and on the relationship of the habitat with the coastline evolution.We consider the resident Snowy Plover(Charadrius alexandrinus nivosus),and the migrant Piping Plover(Charadriusmelodus)and Red Knot(Calidris canutus)along the Gulf Coast of Mexico in Florida.Methods:We analyze and model the coupled dynamics of habitat patches of these imperiled shorebirds and of the shoreline geomorphology dictated by land cover change with consideration of the coastal wetlands.The land cover is modeled from 2006 to 2100 as a function of the A1B sea level rise scenario rescaled to 2 m.Using a maximum-entropy habitat suitability model and a set of macroecological criteria we delineate breeding and wintering patches for each year simulated.Results:Evidence of coupled ecogeomorphological dynamics was found by considering the fractal dimension of shorebird occurrence patterns and of the coastline.A scaling relationship between the fractal dimensions of the species patches and of the coastline was detected.The predicted power law of the patch size emerged from scale-free habitat patterns and was validated against 9 years of observations.We predict an overall 16%loss of the coastal landforms from inundation.Despite the changes in the coastline that cause habitat loss,fragmentation,and variations of patch connectivity,shorebirds self-organize by preserving a power-law distribution of the patch size in time.Yet,the probability of finding large patches is predicted to be smaller in 2100 than in 2006.The Piping Plover showed the highest fluctuation in the patch fractal dimension;thus,it is the species at greatest risk of decline.Conclusions:We propose a parsimonious modeling framework to capture macroscale ecogeomorphological patterns of coastal ecosystems.Our results suggest the potential use of the fractal dimension of a coastline as a fingerprint of climatic change effects on shoreline-dependent species.Thus,the fractal dimension is a potential metric to aid decision-makers in conservation interventions of species subjected to sea level rise or other anthropic stressors that affect their coastline habitat.

A comparative study of the mechanical properties, fracture behavior, creep, and shrinkage of chemically based self-consolidating concrete

This study presents the results of an experimental investigation that compares the mechanical properties, fracture behavior, creep, and shrinkage of a chemically-based self-consolidating concrete （SCC） mix with that of a corresponding conventional concrete （CC） mix. The CC and SCC mix designs followed conventional proportioning in terms of aggregate type and content, cement content, air content, water-cementitiuos materials （w/cm） ratio, and workability. Then, using only chemical admixtures, the authors converted the CC mix to an SCC mix with all of the necessary passing, filling, flowability, and stability requirements typically found in SCC. The high fluidity was achieved with a polycarboxylate-based high-range water-reducing admixture, while the enhanced stability was accomplished with an organic, polymer-based viscosity-modifying admixture. The comparison indicated that the SCC and CC mixes had virtually identical tensile splitting strengths, flexural strengths, creep, and shrinkage. However, the SCC mix showed higher compressive strengths and fracture energies than the corresponding CC mix.

Multiple mechanisms in woodland plant species invasion

Aims A plethora of theories explain species invasion,yet when tested in isolation,support or falsification becomes contingent on study species,system and approach.Our objective was to examine com-munity-level species invasion as a function of multiple competing hypotheses.Methods We used data from>3500 woodland plant species in 2750 plots in 49 national parks in eastern US deciduous forests to test multiple competing theories of species invasion:competition,empty niche,propagule pressure and latitude matching.We also tested interac-tions with residence time to account for non-native species naturali-zation and spread since arrival.Important Findings The non-native herbs generally thrived at latitudes similar to those from which they originated,but not necessarily where they were originally introduced to the eastern US.Overall,we found that each hypothesis explained at least some aspect of woodland plant species invasion,but examining them simultaneously allowed assessment of their relative strengths and interactions.Our results suggested that residence time is a strong predictor of non-native woodland plant success,particularly as it interacts with other mechanisms of inva-sion,such as competition(abundance of native woodland plants),climate matching(similar invaded latitude as home range),prop-agule pressure(distance to putative seed sources)and empty niche(relatedness to native plants).We found that initial barriers,such as distance from propagule source or suboptimal habitat,were over-come,as was resistance from native relatives.However,the biggest challenge for the non-native woodland plants appeared to be time,as they declined after~1 to 2 centuries.

Providing refuges for adult Pacific lamprey Entosphenus tridentatus inside fishways

Fishways at hydroelectric dams are unnatural environments that typically present fish with channels of uniform depth,variable water velocity,and lack of cover.Fish retention and overall passage success may be improved by providing rest and sheltering areas inside fishways.We examined adult Pacific lamprey Entosphenus tridentatus use of two specially designed fishway refuges at Bonneville Dam on the Columbia River(northwestern USA).These relatively small boxes(1.1 m×0.4 m×0.2 m)provided low-velocity,dark refuge from predation for Pacific lamprey,a largely nocturnal species.Refuge boxes were equipped with antennas to detect entry of lamprey tagged with passive integrated transponder(PIT)tags.We PIT tagged and released 3,247 lamprey,including 599 that were double-tagged with a PIT and a radio transmitter,over three study years(2012-2014).In each year,PIT-tagged lamprey detected at nearby fishway exits had used a refuge:12%in 2012,28%in 2013,and 36%in 2014.Median residence time of PIT-tagged lamprey in the refuges for each year was 20.3 h,16.6 h,and 13.1 h.Lamprey entrance into refuges peaked at 0300-0500 PDT,and they typically exited at around 2000 PDT,suggesting that refuges primarily functioned as shelter from daylight.Probability of refuge use increased with a morphological indicator of sexual maturity(distance between dorsal fins).In the radio-tagged group,refuge users were equally likely to pass Bonneville Dam as non-users.However,refuge users were less likely than non-users to be detected at sites upstream from the dam,perhaps owing to their maturation status or longer mean passage time through our study area(2.0 vs.0.6 d for non-users).Refuges show promise for improving fish retention in fishways,particularly for nocturnal and/or small-bodied species that seek shelter from light or predation.

Reimagining large river management using the Resist-Accept-Direct(RAD)framework in the Upper Mississippi River

Background Large-river decision-makers are charged with maintaining diverse ecosystem services through unprec-edented social-ecological transformations as climate change and other global stressors intensify.The interconnected,dendritic habitats of rivers,which often demarcate jurisdictional boundaries,generate complex management chal-lenges.Here,we explore how the Resist–Accept–Direct(RAD)framework may enhance large-river management by promoting coordinated and deliberate responses to social-ecological trajectories of change.The RAD frame-work identifies the full decision space of potential management approaches,wherein managers may resist change to maintain historical conditions,accept change toward different conditions,or direct change to a specified future with novel conditions.In the Upper Mississippi River System,managers are facing social-ecological transformations from more frequent and extreme high-water events.We illustrate how RAD-informed basin-,reach-,and site-scale decisions could:(1)provide cross-spatial scale framing;(2)open the entire decision space of potential management approaches;and(3)enhance coordinated inter-jurisdictional management in response to the trajectory of the Upper Mississippi River hydrograph.Results The RAD framework helps identify plausible long-term trajectories in different reaches(or subbasins)of the river and how the associated social-ecological transformations could be managed by altering site-scale conditions.Strategic reach-scale objectives may reprioritize how,where,and when site conditions could be altered to contribute to the basin goal,given the basin’s plausible trajectories of change(e.g.,by coordinating action across sites to alter habitat connectivity,diversity,and redundancy in the river mosaic).Conclusions When faced with long-term systemic transformations(e.g.,>50 years),the RAD framework helps explicitly consider whether or when the basin vision or goals may no longer be achievable,and direct options may open yet unconsidered potential for the basin.Embedding the RAD framework in hierarchical decision-making clarifies that the selection of actions in space and time should be derived from basin-wide goals and reach-scale objectives to ensure that site-scale actions contribute effectively to the larger river habitat mosaic.Embedding the RAD framework in large-river decisions can provide the necessary conduit to link flexibility and innovation at the site scale with stability at larger scales for adaptive governance of changing social-ecological systems.