Problems Of Water Balance Research Articles

Hazards identification and characterisation of the tailings storage facility dam failure and engineering applications

ABSTRACT To characterise the relationships among the hazards associated with tailings storage facility (TSF) dam failure, interpretive structural modelling (ISM) is used to hierarchise, structuralise and visualise them. Based on evidence, 15 hazards in four categories are identified, and are classified into seven levels and four clusters. The results show that seven hazards can be regarded as the fundamental hazards. The majority of hazards associated with technology factor can be seen as transactional hazards and are closely related to the water balance problem. The proposed ISM method offers theoretical reference and improves risk management for the TSF and the mining industry.

Application research of flue gas depth reduction modification technology in 600MW thermal power unit

According to the policy requirement of No. 156 in 2018, the wet flue gas desulfurization system of a 600 MW unit in a power plant needs to be reformed for deep emission reduction. Based on the technical route of flue gas cooling and condensing, the influencing factors such as exhaust gas temperature and exhaust fan allowance are analyzed, and the design boundary parameters are reasonably selected. The technical characteristics of flue gas condenser and slurry cooler are compared. It is pointed out that slurry cooler has the advantages of no increase in flue gas system resistance, non-stop construction and low energy consumption, and is more suitable for field renovation. Aiming at the water balance problem of desulfurization system after using slurry cooler, this paper combs and analyzes the water balance items, and takes a series of measures: demolishing the first-stage absorber demister, collecting filtrate water and filter cloth washing water for pulping, recovering the slurry circulating pump sealing washing water, etc., which can basically meet the transformation needs. Special-shaped tray is installed in the absorption tower to improve the desulfurization and dust removal performance.

Seventy-year long record of monthly water balance estimates for Earth\u2019s largest lake system

We develop new estimates of monthly water balance components from 1950 to 2019 for the Laurentian Great Lakes, the largest surface freshwater system on Earth. For each of the Great Lakes, lake storage changes and water balance components were estimated using the Large Lakes Statistical Water Balance Model (L2SWBM). Multiple independent data sources, contributed by a binational community of research scientists and practitioners, were assimilated into the L2SWBM to infer feasible values of water balance components through a Bayesian framework. A conventional water balance model was used to constrain the new estimates, ensuring that the water balance can be reconciled over multiple time periods. The new estimates are useful for investigating changes in water availability, or benchmarking new hydrological models and data products developed for the Laurentian Great Lakes Region. The source code and inputs of the L2SWBM model are also made available, and can be adapted to include new data sources for the Great Lakes, or to address water balance problems on other large lake systems.

Empirical correlations for the performance of a PEFC considering relative humidity of fuel and oxidant gases

The growing energy demand and the impact of polluting gases lead to the necessity of alternative energy sources and conversion energy devices. Fuel cells (FCs) appears as a suitable solution for facing the mentioned issues. Predicting the behavior of a polymer electrolyte fuel cell (PEFC) under different conditions represents a proper initial step to solve the several issues, e.g., aging water balance problems, which occur inside the cell during the energy conversion process. Understanding microstructural impacts of the diffusion media, water management issues of FCs or the impacts of the inlet reactant gases to the cell represent some of the processes that have to be analyzed to improve the efficiency and behavior of FCs.The current study aims, based on experimentally collected data, to propose empirical correlations that describe and predict the performance of a PEFC. The single cell considered in this study corresponds to a single PEFC with a Nafion® 112 membrane as electrolyte and with an effective area of 25 cm2. Relative humidity as a function of the reactive inlet gas temperature, as well as the power and the current density as a function of the cell/reactant gas temperature gradient are analyzed. In addition, correlations for power and current density as a function of the relative humidity (RH) have been proposed. Our correlations are obtained for an operating voltage of 0.6 V. It was shown a strong correlation between the power and current densities with the RH since the membrane conductivity depends mainly on the water content. The PEFC behavior was evaluated at different RHs. The results show big losses of operating power and current densities, as well as an increment of the resistance of the membrane when it operates at low RH.

Analysis of Problems in Soil Source Heat Pump

The soil source heat pump system is characterized by high efficiency, energy saving, environmental protection, and full use of renewable energy. And today, when excessive energy consumption puts tremendous pressure on the environment, it has increasingly become the focus of attention. Most of the research aimed at it so far has focused on heat exchange, but there is almost no water balance problem. And many studies only draw some conclusions based on some theoretical calculations or numerical simulations. As a result, there have been many studies on the problem of heat transfer, and the research has deviated from the actual focus on theory and hydraulic balance. For the entire system, there is almost no comprehensive consideration of thermal balance, hydraulic balance, and economics. Therefore, this paper discusses the problems existing in the above three aspects of the soil source heat pump system, and then has some reference value for the actual project

Effect of cold storage on stomatal functionality, water relations and flower performance in cut roses

Symptoms of water stress are the most frequent cause for the “end of vase life” in prior stored roses. It was hypothesized that dark storage may alter the stomatal functionality and may cause water balance problems during the subsequent vase life period. The effect of short- and long-term storage on functionality of stomatal and subsequent flower performance was investigated in two rose cultivars (cvs) (‘Akito’ and ‘Grand Prix’) with presumed different sensitivity for development of water stress symptoms during the vase life.Compared to no storage, both short term storage (2.3d at 6°C) and long term storage (28d at 0.5°C) negatively affected the stomatal functionality in cultivar (cv) Akito. Stomatal functionality parameters such as the rapidity of the closing response upon dehydration and the relative water content at which stomata are fully closed showed good correlations with flower performance parameters (flower weight changes and vase life). This indicates that in cv Akito, the decreased stomatal functionality is one of the factors involved in the poor vase life of prior stored flowers. In cv Grand Prix, however, storage did not greatly affect the stomatal functionality but storage negatively affected flower performance in a comparable way as in cv Akito.A pre-treatment with abscisic acid prior to storage slightly improved stomatal functionality in both cvs, but no clear effect on flower performance was observed. Addition of the bactericide 8-HQC to the vase water improved flower performance in both cvs but could not alleviate the negative effect of cold storage on flower performance.Results show that in roses cold storage may, depending on the cultivar, negatively affect stomatal functionality and this may contribute to water stress and ultimately flower failure. In addition, cold storage may negatively affect xylem water conducting properties through processes not related to bacterial contamination.

Approaching 2 W∙cm-2 AEMFCs through Electrode Engineering and Controlling the Cell Water Content and Balance

In recent years, advances in alkaline exchange membrane fuel cells (AEMFCs) with anion exchange membrane (AEM) solid polymer electrolytes have gained traction due to their distinct – and potentially game-changing – advantages over proton exchange membrane fuel cells. However, AEMs and AEMFCs are at a significantly less mature stage in their developmental than proton exchange membrane fuel cells (PEMFCs), and have experienced limitations specifically in the area of stability, carbonation, and achievable current and power densities, exhibiting a sizable performance gap vs PEMFCs.1 This talk will focus on several fundamental and engineering advances that have enabled the creation of AEMFCs that are able to achieve up to 1.9 W∙cm-2 peak power (> 2 W∙cm-2 iR-corrected) and 100’s of hours of stable operation, bringing AEMFCs much closer to the incumbent PEMFC technology, and opening the way to overcome the cost barrier that has slowed the growth and large scale market implementation of fuel cells in the transportation sector.2 One of the largest contributors to the challenges faced in AEMFCs is the cell water content and balance, where the role of water has an impact on the anode (generation through the hydrogen oxidation reaction), cathode (consumption through the oxygen reduction reaction), and movement from the cathode to anode through electro-osmotic drag. This results in a significantly larger current-driven movement of water than PEMFCs, where less water required for the transport of the protons and there is no electrochemical consumption, and a need to provide adequate water to maintaining proper ionomer and membrane hydration while avoiding catalyst layer flooding or dry-out. Back diffusion of water from anode to cathode in the AEMFC, which is coupled to the membrane conductivity, is a promising way to decrease the extreme water gradient, and simplify the water balance problem in AEMFCs.3 In this study, we will discuss the influence of the membrane, ionomer and gas diffusion layer as well as the flow rate and dew points of the anode and cathode gases on AEMFC performance. Using a hydrophilic gas diffusion layer without a microporous layer increases membrane hydration, but also increases the possibility for flooding. Catalyst layer engineering – through adjusting the carbon/ionomer/catalyst loadings, adjusting hydrophilicity/hydrophobicity, manipulating electrode thickness and porosity, etc. – is investigated. We will also discuss controlling the total amount of water fed to the AEMFC through the gas feeds, as well as the water balance between the anode and cathode. Manipulating the dew points led to the counter-intuitive discovery that the cell performs better with the humidity higher at the anode than the cathode, despite water generation and electro-osmotic drag towards that electrode. In fact, removing too much water from the anode caused instability in the cell, while increasing the water at the anode decreased the membrane resistivity. Water back diffusion from the anode to the cathode likely plays an important role in membrane hydration and hydroxide transport through the membrane. Finally, we will also discuss the behavior of the AEM and powder anionomer in the presence of air both with and without CO2.

Wavy Surface Cathode Gas Flow Channel Effects on Transport Processes in a Proton Exchange Membrane Fuel Cell

The flow field design of current collectors is a significant issue, which greatly affects the mass transport processes of reactants/products inside fuel cells. Especially for proton exchange membrane (PEM) fuel cells, an appropriate flow field design is very important due to the water balance problem. In this paper, a wavy surface is employed at the cathode flow channel to improve the oxygen mass transport process. The effects of wavy surface on transport processes are numerically investigated by using a three-dimensional anisotropic model including a water phase change model and a spherical agglomerate model. It is found that the wavy configurations enhance the oxygen transport and decrease the water saturation level. It is concluded that the predicted results and findings provide the guideline for the design and manufacture of fuel cells.

Evaluation of Climate Input Biases and Water Balance Issues Using a Coupled Surface–Subsurface Model

A physically based, coupled and distributed hydrologic model has been set up for the Ringkøbing Fjord catchment, Denmark. This transient model, built with the MIKE SHE/MIKE 11 code, comprises all major components of the terrestrial water cycle, including a three‐dimensional finite‐difference groundwater model. The dynamic coupling of the hydrologic processes secures physically sound feedback and makes the model an ideal tool for evaluating the overall water balance and quantifying potential water balance issues. Historically, failure to obtain water balance closure has been a persistent and much debated problem in Denmark, presumably arising mainly from uncertainties in precipitation, actual evapotranspiration, and groundwater flow to the sea. In this study, the water balance issues were addressed within the modeling framework through analysis of different rain gauge catch corrections and potential evapotranspiration input. The analysis focused on the effect of different rain gauge catch corrections on the model performance, the optimized parameter sets, and state variables not included in the model calibration. The results suggest that water balance problems can be reduced by using a dynamic rain gauge catch correction based on daily wind speed and temperature fields. The model optimization and performance evaluation revealed, however, that several parameter sets gave similar performance compared with the observed groundwater head and river discharge data but still resulted in significant differences with respect to internal water fluxes such as evapotranspiration, groundwater recharge, and stream flow components. New observational data are needed to constrain the model further and thus reduce the water balance uncertainties convincingly.

Regionalization of precipitation and air temperature over high-altitude catchments – learning from outliers

Closing the water balance of mountainous catchments may sometimes become tricky, even before applying a hydrological model. In this paper, we focus on mountainous, snow-affected catchments and try to understand the reasons for the “unrealistic” hydrological behaviours that they sometimes show: when annual runoff is greater than the annual areal precipitation estimate, something is obviously wrong, but finding the appropriate means to adjust the water balance is far from a trivial matter. This paper aims to improve our knowledge of the water balance of mountainous and snow-affected catchments in two different countries: Sweden and France. We use a simple non-dimensional framework to detect outliers and then propose an regionalization of precipitation and air temperature in order to better estimate inputs over high-altitude catchments. Since we are interested in catchment water balance, we evaluate our regionalized input estimates by comparing them to streamflow measurements. The results are mixed: in Sweden, our approach is successful because it can make most outlier catchments become regular ones; but in France it is disappointing because it does not solve most of the water balance problems identified. However, for both countries, the regionalization approach significantly improves the performance of a rainfall–runoff model at a daily time step. Citation Valéry, A., Andréassian, V. & Perrin, C. (2010) Regionalization of precipitation and air temperature over high-altitude catchments – learning from outliers. Hydrol. Sci. J. 55(6), 928–940.

Thermoregulatory Behavior in Migratory European Bee-eaters (Merops apiaster)

Abstract Birds in hyper-arid environments have acute problems of energy and water balance, and thermoregulate both physiologically and behaviorally. I report on European Bee-eaters (Merops apiaster) engaged in a previously unreported thermoregulatory behavior of diving into the sea and in salt ponds with high levels of salinity. This behavior may also explain the previously reported, but unexplained, finding of bee-eaters inside a tiger shark (Galeocerdo cuvier) in the Red Sea. These observations should instigate future experiments on the subject of selective use of salt water for evaporative cooling and thermoregulatory behavior by desert birds.

Variations in body melanization impact desiccation resistance inDrosophila immigransfrom Western Himalayas

AbstractEctothermic species face problems of water balance under colder and drier climatic conditions in montane localities. We investigated five ecophysiological traits (body melanization, desiccation resistance, rate of water loss or gain and body size) in eight populations ofDrosophila immigransfrom an altitudinal gradient (600–2226 m) in the Western Himalayas. The traits showed bell‐shaped variability patterns characteristic of quantitative traits. For body melanization, we observed high heritability (0.65) on the basis of parent–offspring regression. A comparison of highland versus foothill populations showed significant divergence for all the traits except body size. Darker flies from the highlands exhibited higher desiccation resistance but reduced rate of water loss or gain as compared with lighter flies from the foothills, which showed lower desiccation resistance and higher rates of water loss as well as gain. Lack of differences in the amount of epicuticular lipids cannot account for differential reduction in cuticular water loss in altitudinal populations. However, within‐ as well as between‐population differences in body melanization can account for changes in desiccation resistance and reduction in cuticular water loss. Analyses of highland versus lowland populations as well as in assorted darker and lighter flies from a highland population have shown differences in haemolymph and dehydration tolerance. For the mechanistic basis of desiccation resistance, our results on wild populations ofDrosophila immigransare not in agreement with those reported for laboratory‐selected desiccation‐resistant strains inDrosophila melanogaster. Thus, ecophysiological mechanisms could be different under laboratory versus field selection.

Priority environmental issues for monitoring - mismatch between farmers and catchment management perspectives

Monitoring is an essential part of an environmental management system (EMS) if landholders are to demonstrate improved environmental performance. This paper reports results of two surveys to determine environmental issues and priorities for monitoring. The first survey was conducted on 12 EMS pilot projects, and the second on 18 catchment management organisations in Australia. With the exception of pastoral zones, EMS facilitators identified moderate to major issues in land condition, water balance, riparian zone, native vegetation condition and pests. Water quality issues were rated as minor to moderate problems. Issues raised by the greatest number of respondents were water balance problems and weed and pest issues. Catchment managers reported widespread degradation issues in land condition, water balance problems, altered water flow, water quantity and availability and water quality. Degradation of the riparian zone and native vegetation were also reported. Both EMS facilitators and catchment management organisations understood the need for environmental monitoring; however, few EMS pilot projects have addressed it. This was due, in part, to a lack of readily available tools and concentration on the EMS process itself. Tools of most interest to facilitators were soil erosion risk, soil test interpretation, soil structure assessment, soil health, water leakage and perenniality, water quality, riparian zone management, herbicide resistance, greenhouse emissions and energy use. Facilitators also suggested that tools should be delivered in several formats, but workshops delivered by experts were of most interest. Catchment managers had realistic and pragmatic views about the role of landholder monitoring in assessing catchment outcomes and there is a mismatch between landholder monitoring and catchment reporting requirements. Landholders are likely to monitor only what is in their direct interests and this will be mainly on land condition. We conclude that on-farm environmental monitoring conducted by landholders will be of limited use for catchment management organisation reporting. However, it will be very important in helping farmers to make more informed decisions about their environmental management, together with education and support. The issue of catchment condition monitoring and reporting requires serious attention as current monitoring and reporting is likely to be inadequate.

Ecophysiology of juvenile California halibut Paralichthys californicus in relation to body size, water temperature and salinity

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 243:235-249 (2002) - doi:10.3354/meps243235 Ecophysiology of juvenile California halibut Paralichthys californicus in relation to body size, water temperature and salinity Sharook P. Madon* Pacific Estuarine Research Laboratory, San Diego State University, San Diego, California 92182-1870, USA *E-mail: smadon@perl.sdsu.edu ABSTRACT: Food consumption, metabolism, growth, conversion efficiencies (food assimilation, gross and net growth) and whole-body water content of small (118 to 172 mm TL) and large (237 to 310 mm TL) juvenile California halibut Paralichthys californicus exposed to various combinations of water temperatures (14, 20, 25 and 28°C) and salinities (8, 17 and 34 ppt) were quantified in laboratory experiments. Small juvenile halibut were able to grow and maintain water balance over almost the entire ranges of water temperatures and salinities tested, except at 14°C and 8 ppt, where they lost weight but gained about 2% body water. Large juvenile halibut were far less tolerant of variations in water temperature and salinity. Regardless of salinity, large juvenile halibut exposed to 14 and 25°C lost weight due to greatly reduced energy intake, and experienced >90% mortality at 28°C; in diluted seawater at 14 and 25°C they also experienced water balance problems. Only at 20°C did surplus energy and lack of water balance problems allow large juvenile halibut to grow across all salinities. Differences in energetic and water balance responses of small and large juvenile halibut correspond to the habitat preferences of each size group. Small juvenile halibut are estuarine, and their ability to tolerate wide variations in water temperatures and salinities allows them to exploit estuaries and coastal lagoons with abundant small prey (gobies), warm temperatures, and few predators. However, in winter, with the increased probability of estuarine or lagoon mouth closures, water temperatures and salinity can rapidly drop to levels unfavorable for growth of small juvenile halibut. Large juvenile halibut, with their reduced tolerance for varying temperatures and salinities, must migrate from lagoons and estuaries into open-coast environments, where they also benefit from abundant large prey. Closure of river mouths likely pose the greatest risk to large juvenile halibut, should they become trapped in cold, hyposaline coastal wetlands. KEY WORDS: Mouth closures · Flatfish · Bays · Energetics · Physiological ecology Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 243. Online publication date: November 13, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

SUBSURFACE FLOW IN A STREAM WITH ALTERNATE SANDBARS

The flow exchange between open channel and alternate sandbar is important for instream ecosystems, water balance and water quality problems investigations. Both experimental and numerical investigations are done to get relationships between surface and subsurface flowin longitudinal and transverse direction. Under steady low flow condition, strong effects of surfaceflow conditions on subsurface flow structures in the alternate sandbars are recognized through experiments as:(1) Longitudinal flow is dominant, but the longitudinal distribution of subsurface water elevations depend on surface flow conditions.(2) Transverse gradient of subsurface flow varies by surface water discharge and bed shape. Three types of subsurface flow patterns are recognized to define flowexchange between stream and sandbar. Numerical simulations using 2-D theory shows good fit with the experimental results and field data.

Temperature and water relations in desert bees

1. 1. Desert bees do not show significant differences in most thermal parameters; mean endothermic warm-up rates are similar to those of temperate species, with no special cooling mechanisms, and normal upper critical temperatures (unlike desert ants and beetles). Thermoregulatory abilities may however be improved. 2. 2. They show the whole range of possible water balance problems; small species are acutely water-stressed when foraging, but large bees suffer from excessive generation of metabolic water in flight. 3. 3. Activity patterns are therefore either matinal, crepuscular or bimodal; essentially desert bees avoid heat and adapt to cold desert dawns and dusks. Desert plants must be coevolved to offer appropriate rewards and match the physiological constraints on their pollinators. 4. 4. Endothermy in bees may have evolved primarily in arid zones, and served as a pre-adaptation for subsequent invasion of cool temperate biomes.

A Tribute to Charles Richard Taylor

A Tribute to Charles Richard Taylor

Metabolic constraints on long-distance migration in birds

The flight range of migrating birds depends crucially on the amount of fuel stored by the bird prior to migration or taken up en route at stop-over sites. However, an increase in body mass is associated with an increase in energetic costs, counteracting the benefit of fuel stores. Water imbalance, occurring when water loss exceeds metabolic water production, may constitute another less well recognised problem limiting flight range. The main route of water loss during flight is via the lungs; the rate of loss depends on ambient temperature, relative humidity and ventilatory flow and increases with altitude. Metabolite production results in an increased plasma osmolality, also endangering the proper functioning of the organism during flight. Energetic constraints and water-balance problems may interact in determining several aspects of flight behaviour, such as altitude of flight, mode of flight, lap distance and stop-over duration. To circumvent energetic and water-balance problems, a bird could migrate in short hops instead of long leaps if crossing of large ecological barriers can be avoided. However, although necessitating larger fuel stores and being more expensive, migration by long leaps may sometimes be faster than by short hops. Time constraints are also an important factor in explaining why soaring, which conserves energy and water, occurs exclusively in very large species: small birds can soar at low speeds only. Good navigational skills involving accurate orientation and assessment of altitude and air and ground speed assist in avoiding physiological stress during migration.

Water Content of Prey of Nestling Blue Tits in a Corsican Habitat

Caterpillars are important prey for tits (Parus spp.), including Corsican blue tits. It is hypothesized that the low abundance of water-rich caterpillars in combination with high temperatures, especially at the end of the breeding season, cause problems of water balance for the nestlings in the Corsican population. Tits were expected to prefer feeding their young with water-rich prey. The three most important groups of prey (caterpillars [82.8% water], grasshoppers [78.9%] and spiders [69.1%]) differ significantly in water content. The water content of grasshoppers was much higher than expected from the literature. From previous studies it was known that, apart from caterpillars (20-60% of the prey items), tits prefer feeding their nestlings with spiders (26-40%) rather than with grasshoppers (5-17%). This unexpected result is discussed within the framework of a cost-benefit analysis of prey choice, mainly with respect to prey availability.

The aquaporin family of water channels in kidney

The longstanding puzzle of membrane water permeability was advanced by the discovery of channel-forming integral protein (CHIP). This protein was shown to function as a water channel when expressed in Xenopus oocytes or when reconstituted into synthetic membranes. Site-directed mutagenesis and electron crystallography reveal tetrameric organization of CHIP, and the two halves of CHIP are tandem repeats folded into an obversely symmetric structure which resembles an hourglass. Each tetramer is comprised of functionally independent subunits. CHIP is the archetypal member of a newly-recognized family of membrane water transporters known as the "Aquaporins" (AQPs). AQP1 (CHIP) is abundant in the apical and basolateral membranes of renal proximal tubules and descending thin limbs, and is also present in a number of extra renal tissues. In the collecting duct, AQP2 is the predominant vasopressin-sensitive water channel. AQP2 is localized in the apical membrane and in intracellular vesicles which are targeted to the apical plasma membranes when stimulated by antidiuretic hormone. Humans are identified with mutations in AQP1 and AQP2 and exhibit contrasting clinical phenotypes. AQP3 resides in the basolateral membranes of collecting duct principal cells providing an exit pathway for water, and AQP4 is abundant in brain, where it apparently functions as the hypothalamic osmoreceptor responsible for secretion of antidiuretic hormone. Continued analysis of the aquaporins is providing detailed molecular insight into the fundamental physiological problems of water balance and water balance disorders.