Literatura académica sobre el tema "Low-energy rivers"
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Artículos de revistas sobre el tema "Low-energy rivers":
1
Menting, Foeke y Erik W. Meijles. "Local Factors Determining Spatially Heterogeneous Channel Migration in a Low-Energy Stream". Water 11, n.º 10 (16 de octubre de 2019): 2149. http://dx.doi.org/10.3390/w11102149.
Resumen
Since the 1990s, nature and water management policies have attempted to re-create natural rivers systems by mimicking curvy meandering planforms, based on the assumption that meandering is the natural channel-forming process. However, in low-energy river systems, the extent to which meandering plays a natural role is often minimal. This study aims to quantify contemporary lateral migration in the low-energy irregular sinuous lowland river system of the Drentsche Aa, The Netherlands, and to determine the factors influencing lateral channel migration in a heterogeneous valley fill. Although the river is classified as laterally immobile based on an empirical stability diagram, field observations prove that erosion and deposition are currently occurring. By analyzing historical and present-day maps, it was shown that lateral migration was highly spatially variable for the period 1924–2005. Sinuosity and valley gradient are not correlated to lateral migration rates, suggesting they are not a measure of lateral migration in the case study area, which is in line with the literature. Based on geomorphological and soil map analyses, it was shown that lateral migration rates are significantly higher in valley fills of aeolian sands than in clastic alluvial deposits, which on their turn are significantly higher than in peaty environments. Therefore, local conditions appear to be dominant over other factors such as stream power and bed grain size. These findings are important for river rehabilitation of low-energy rivers, because it shows that local valley fill conditions can greatly influence active lateral migration in the river.
2
Lakeh, Reza Baghaei, Christopher Salerno, Ega P. Herlim, Joseph Kiriakos y Saied Delagah. "Repurposing Reverse Osmosis Concentrate as a Low-Cost Thermal Energy Storage Medium". Journal of Clean Energy Technologies 8, n.º 4 (octubre de 2020): 31–40. http://dx.doi.org/10.18178/jocet.2020.8.4.522.
Resumen
The reject of the reverse osmosis water treatment process (aka brine, concentrate, ROC) is a mixture of salts that are dissolved in high salinity water. The ROC is classified as an industrial waste by the U.S. Environmental Protection Agency and can face regulatory limitations on disposal. State-of-the-art of ROC disposal includes deep-well injection, surface discharge to rivers, discharge to the ocean, and evaporation ponds. In this study, the feasibility of using Reverse Osmosis Concentrate as a low-cost Thermal Energy Storage (TES) medium is explored by a techno-economic analysis. The normalized cost of TES (cost per unit volume of stored thermal energy) is estimated through a series of cost analyses and is compared to the cost targets of the U.S. Department of Energy for low-cost thermal energy storage. It was shown that the normalized cost of TES using ROC salt content is in the range of $6.11 to $8.73 depending on ROC processing methods.
3
Candel, Jasper H. J., Bart Makaske, Niels Kijm, Maarten G. Kleinhans, Joep E. A. Storms y Jakob Wallinga. "Self‐constraining of low‐energy rivers explains low channel mobility and tortuous planforms". Depositional Record 6, n.º 3 (19 de mayo de 2020): 648–69. http://dx.doi.org/10.1002/dep2.112.
4
Yuskar, Yuniarti y Tiggi Choanji. "Uniqueness Deposit of Sediment on Floodplain Resulting From Lateral Accretion on Tropical Area". Journal of Geoscience, Engineering, Environment, and Technology 2, n.º 1 (1 de marzo de 2017): 14. http://dx.doi.org/10.24273/jgeet.2017.2.1.12.
Resumen
Kampar rivers has a length of 413 km with average depth of 7.7 m and width of 143 m. Sixty percent of this rivers are meandering fluvial system which transport and deposit a mixture of suspended and bed-load (mixed load) along low energy. River channel that moving sideways by erosion is undergoing lateral migration and the top of the point bar becomes the edge of the floodplain and the fining-upward succession of the point bar will be capped by overbank deposits of Kampar River. Along the Kampar Rivers, there are more than 60% of floodplain sediments and almost all of the floodplain formed by bend migration on the suspended-load channels of Kampar watershed. This formation consist of succession of fine to medium sand and silt/mud, with root traces, that form as drapes on the prograding bank. These beds dip mostly channel wards and quickly wedge out as they grade up and onto the floodplain. The depositional model is presented showing how lateral accretion can make a significant contribution to the preservation of fine-grained within channel deposits in contemporary floodplains. The examples presented here demonstrate that analogues to ancient point-bar deposits containing alternating sandstone and shale sequences are common in the low-energy fluvial environments of Riau rivers especially Kampar rivers.
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Restrepo, Juan Camilo, Aldemar Higgins, Jaime Escobar, Silvio Ospino y Natalia Hoyos. "Contribution of low-frequency climatic–oceanic oscillations to streamflow variability in small, coastal rivers of the Sierra Nevada de Santa Marta (Colombia)". Hydrology and Earth System Sciences 23, n.º 5 (16 de mayo de 2019): 2379–400. http://dx.doi.org/10.5194/hess-23-2379-2019.
Resumen
Abstract. This study evaluated the influence of low-frequency oscillations, that are linked to large-scale oceanographic–atmospheric processes, on streamflow variability in small tropical coastal mountain rivers of the Sierra Nevada de Santa Marta, Colombia. We used data from six rivers that had > 32 years of complete, continuous monthly streamflow records. This investigation employed spectral analyses to (1) explore temporal characteristics of streamflow variability, (2) estimate the net contribution to the energy spectrum of low-frequency oscillations to streamflow anomalies, and (3) analyze the linkages between streamflow anomalies and large-scale, low-frequency oceanographic–atmospheric processes. Wavelet analyses indicate that the 8–12-year component exhibited a quasi-stationary state, with a peak of maximum power between 1985 and 2005. These oscillations were nearly in phase in all rivers. Maximum power peaks occurred for the Palomino and Rancheria rivers in 1985 and 1995, respectively. The wavelet spectrum highlights a change in river variability patterns between 1995 and 2015, characterized by a shift towards the low-frequency oscillations' domain (8–12 years). The net contribution of these oscillations to the energy spectrum was as high as 51 %, a value much larger than previously thought for rivers in northwestern South America. The simultaneous occurrence of hydrologic oscillations, as well as the increase in the amplitude of the 8–12-year band, defined periods of extremely anomalous wet seasons during 1989–1990, 1998–2002 and 2010–2011, reflecting the role of low-frequency oscillations in modulating streamflow variability in these rivers. Cross-wavelet transform and wavelet coherence revealed high common powers and significant coherences in low-frequency bands (>96 months) between streamflow anomalies and Atlantic Meridional Oscillation (AMO), Pacific Decadal Oscillation (PDO) and the Tropical North Atlantic Index (TNA). These results show the role of large-scale, low-frequency oceanographic–climate processes in modulating the long-term hydrological variability of these rivers.
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Naidu, L. D., S. Saravanan, M. Chidambaram, Mukesh Goel, Ashutosh Das y J. Sarat Chandra Babu. "Nanofiltration in Transforming Surface Water into Healthy Water: Comparison with Reverse Osmosis". Journal of Chemistry 2015 (2015): 1–6. http://dx.doi.org/10.1155/2015/326869.
Resumen
The natural surface water, especially available through rivers, is the main source of healthy water for the living beings throughout the world from ancient days as it consists of all essential minerals. With the advent of industrialization, gradually even the most prominent rivers have been polluted in all parts of the world. Although there are lots of technologies, nanofiltration (NF) has been chosen to transform river water into healthy water due to its unique advantages of retaining optimum TDS (with essential minerals required for human body), consuming of lower energy, and no usage of any chemicals. The prominent parameters of surface water and macro/microminerals of treated water have been analyzed. It is shown that NF is better in producing healthy water with high flux by consuming low energy.
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Sheikh, Shakil Rehman, Syed Hassan Raza Shah, Umar Rauf, Fawad Rauf, Zareena Kausar, Umair Aziz, Muhammad Faizan Shah, Haseeb Yaqoob y Muhammad Bilal Khan Niazi. "A Low-Cost Sustainable Energy Solution for Pristine Mountain Areas of Developing Countries". Energies 14, n.º 11 (28 de mayo de 2021): 3160. http://dx.doi.org/10.3390/en14113160.
Resumen
The rise in energy requirements and its shortfall in developing countries have affected socioeconomic life. Communities in remote mountainous regions in Asia are among the most affected by energy deprivation. This study presents the feasibility of an alternate strategy of supplying clean energy to the areas consisting of pristine mountains and forest terrain. Southeast Asia has a much-diversified landscape and varied natural resources, including abundant water resources. The current study is motivated by this abundant supply of streams which provides an excellent environment for run-of-river micro vertical axis water turbines. However, to limit the scope of the study, the rivers and streams flowing in northern areas of Pakistan are taken as the reference. The study proposes a comprehensive answer for supplying low-cost sustainable energy solutions for such remote communities. The suggested solution consists of a preliminary hydrodynamic design using Qblade, further analysis using numerical simulations, and finally, experimental testing in a real-world environment. The results of this study show that the use of microturbines is a very feasible option considering that the power generation density of the microturbine comes out to be approximately 2100 kWh/year/m2, with minimal adverse effects on the environment.
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Lohani, Sunil Prasad y Andrew Blakers. "100% renewable energy with pumped-hydro-energy storage in Nepal". Clean Energy 5, n.º 2 (13 de mayo de 2021): 243–53. http://dx.doi.org/10.1093/ce/zkab011.
Resumen
Abstract A radical transformation of the global energy system is underway. Solar photovoltaics and wind now comprise three-quarters of the global net new electricity-generation-capacity additions because they are cheap. The deep renewable electrification of energy services including transport, heating and industry will allow solar and wind to largely eliminate fossil fuels over the next few decades. This paper demonstrates that Nepal will be able to achieve energy self-sufficiency during the twenty-first century. Nepal has good solar and moderate hydroelectric potential but has negligible wind- and fossil-energy resources. The solar potential is about 100 times larger than that required to support a 100% solar-energy system in which all Nepalese citizens enjoy a similar per-person energy consumption to developed countries, without the use of fossil fuels and without the environmental degradation resulting from damming Nepal’s Himalayan rivers. Nepal has vast low-cost off-river pumped hydro-energy-storage potential, thus eliminating the need for on-river hydro storage and moderating the need for large-scale batteries. Solar, with support from hydro and battery storage, is likely to be the primary route for renewable electrification and rapid growth of the Nepalese energy system.
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Candel, Jasper H. J., Maarten G. Kleinhans, Bart Makaske, Wim Z. Hoek, Cindy Quik y Jakob Wallinga. "Late Holocene channel pattern change from laterally stable to meandering – a palaeohydrological reconstruction". Earth Surface Dynamics 6, n.º 3 (31 de agosto de 2018): 723–41. http://dx.doi.org/10.5194/esurf-6-723-2018.
Resumen
Abstract. River channel patterns may alter due to changes in hydrological regime related to changes in climate and/or land cover. Such changes are well documented for transitions between meandering and braiding rivers, whereas channel pattern changes between laterally stable and meandering rivers are poorly documented and understood. We hypothesize that many low-energy meandering rivers had relatively low peak discharges and were laterally stable during most of the Holocene, when climate was relatively stable and human impact was limited. Our objectives in this work are to identify a Late Holocene channel pattern change for the low-energy Overijsselse Vecht river, to develop and apply a novel methodology to reconstruct discharge as a function of time following a stochastic approach, and to relate this channel pattern change to reconstructed hydrological changes. We established that the Overijsselse Vecht was laterally virtually stable throughout the Holocene until the Late Middle Ages, after which large meanders formed at lateral migration rates of about 2 m yr−1. The lateral stability before the Late Middle Ages was constrained using a combination of coring information, ground-penetrating radar (GPR), radiocarbon (14C) dating, and optically stimulated luminescence (OSL) dating. We quantified bankfull palaeodischarge as a function of time based on channel dimensions that were reconstructed from the scroll bar sequence and channel cut-offs using coring information and GPR data, combined with chronological constraints from historical maps and OSL dating. We found that the bankfull discharge was significantly greater during the meandering phase compared to the laterally stable phase. Empirical channel and bar pattern models showed that this increase can explain the channel pattern change. The bankfull discharge increase likely reflects climate changes related to the Little Ice Age and/or land use changes in the catchment, in particular as a result of peat reclamation and exploitation.
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Penczak, T., A. A. Agostinho, N. S. Hahn, R. Fugi y L. C. Gomes. "Energy budgets of fish populations in two tributaries of the Paraná River, Paraná, Brazil". Journal of Tropical Ecology 15, n.º 2 (marzo de 1999): 159–77. http://dx.doi.org/10.1017/s0266467499000735.
Resumen
The energy budget of all fish populations was estimated in two small tributaries of the Paraná River (Paraná, Brazil). Total energy consumed by fish in the Caracu and the Agua do Rancho Rivers was 4.1 and 1.8 MJ m−2 y−1, and food items consumed were 2284 and 994.5 g wet weight m−2 y−1, respectively. The gross (K1) and net (K2) ecological efficiency coefficients were very low, but 43.2 and 59.6% of the total fish diet in these two streams, respectively, consisted of plant detritus. In both fish communities, omnivorous (opportunist) species dominated and specialists were rare. Although the Caracu River was more affected by human activity than was the Agua do Rancho, ecological efficiency coefficients calculated for the dominant fish populations were not significantly different.
Tesis sobre el tema "Low-energy rivers":
1
Duquesne, Amélie. "Trajectoire d’évolution d’un cours d’eau à faible énergie au cours du second Holocène : La Charente entre Angoulême et Saintes". Thesis, La Rochelle, 2021. http://www.theses.fr/2021LAROS028.
Resumen
Ce travail propose d’étudier le fleuve Charente, un cours d’eau à faible énergie, entre Angoulême et Saintes afin d’améliorer les connaissances sur le fonctionnement des cours d’eau à faible énergie et notamment de l’anastomose. Les objectifs principaux sont de retracer la trajectoire d’évolution du fleuve Charente à l’échelle multiséculaire et de déterminer le rôle des forçages anthropiques, des héritages géomorphologiques et de la variabilité hydro-climatique dans sa trajectoire ; et d’expliquer l’origine et le maintien de l’anastomose sur la section amont (Angoulême-Cognac). La méthode repose sur une approche géohistorique, géomorphométrique et géomorphologique. Les résultats démontrent 1) une métamorphose fluviale d’un style en tresses pré-holocène vers un style anastomosé sur la section amont ; 2) une simplification de l’anastomose susceptible de commencer dès le Néolithique final et l’Âge du Bronze ; 3) une influence fluvio-marine sur la section aval pendant l’Atlantique ancien et le milieu du Subboréal et 4) un hiatus documentaire sur les périodes de changement climatique rapide. Les résultats géohistoriques révèlent une stabilité globale des formes fluviales sur la période récente et probablement sur le long terme. Cette conclusion peut être nuancée. Les résultats montrent 1) une simplification de la structure fluviale sur la période récente (principalement fin XVIIIe-fin XIXe siècles) dépendante de la trajectoire d’anthropisation du cours d’eau et de la variabilité hydro-climatique et 2) une complexification de la mosaïque fluviale à l’échelle locale au XXe siècle attribuée à l’abandon des pratiques d’entretien du cours d’eau et aux variations du régime de cruesThis work proposes to study the Charente river, a low-energy river, between Angoulême and Saintes for enhance knowledge on the functioning of low-energy rivers and in particular the anastomosis. The main aims are to analyze the evolutionary trajectory of the Charente river on a multisecular timescale and identify the anthropogenic controls, geomorphological heritages and hydro-climatic variability in its trajectory ; and explain the genesis and the conservation of the anastomosis on the upstream section (Angoulême-Cognac). The method is based on a geohistorical, geomorphometrical and geomorphological approach. Results show a fluvial metamorphosis from a braiding pattern pre-Holocene to anastomosing pattern on the upstream section; a simplification of anastomosing pattern potentially begin to the Final Neolithic and the Bronze Age; a fluvio-marine influence on the downstream section during the Atlantic and the mid-Subboreal; and 4) a documentary hiatus on the rapid climate change periods. Geohistoric results expose a global stability of fluvial forms over the recent period and probably on the long-term. This conclusion needs to be nuanced. Results highlight 1) a simplification of the pattern fluvial between the recent period (mainly late 18th / late 20th centuries) dependent on the anthropisation trajectory of river and the hydro-climatic variability and 2) a complexification of the fluvial mosaic at local level during the 20th century attributed to cessation of river maintenance practices and variations of flood regime
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Michler, Luc. "Impacts hydromorphologiques et sédimentaires du décloisonnement de l'Yerres : identification, quantification, spatialisation". Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC074/document.
Resumen
Le bassin-versant de l’Yerres (1030 km²) est localisé au sud-est de l’agglomération parisienne et s’étend sur le plateau de Brie au relief très modéré. Ses caractéristiques physiographiques et sa situation géographique confèrent au lit de l’Yerres une très faible pente (0,009 %), entravée par une forte segmentation longitudinale (0,5 ouvrage/km). Cette dernière est ancienne (moulins hydrauliques) ou plus récente (barrages mobiles) et s’est généralement accompagnée d’une chenalisation du lit. Les perturbations engendrées par ces ouvrages et les modifications morphologiques du lit ont provoqué une altération considérable de la dynamique fluviale et de la diversité morphologique du cours d’eau. Dans ce contexte d’un cours d’eau de faible énergie (< 10 W/m²) fortement artificialisé, notre recherche s’est attachée à évaluer l’efficience de l’effacement de trois barrages à clapets mobiles (h < 3 m) sur la restauration hydromorphologique du lit. À cet effet, des suivis topographique et sédimentologique à haute résolution spatio-temporelle ont été mis en œuvre entre 2015 et 2017 afin d’appréhender les réajustements du système fluvial à partir de l’évolution des caractéristiques morphologiques et granulométriques de son lit. Ils ont dévoilé un remblaiement alluvial se produisant principalement sous la forme de banquettes latérales de vases, à l’exception du site d’Ozouer (le plus en amont). Sur ce dernier le remblaiement alluvial sableux est plus généralisé. À la suite des abaissements hivernaux, celui-ci a fait l’objet des changements morphologiques les plus prononcés, caractérisés par une érosion marquée du fond du lit de la retenue et un faible alluvionnement en aval. Les réajustements morphologiques restent toutefois modérés compte tenu des débits exceptionnellement forts sur la période de suivi et semblent par ailleurs être subordonnés à la présence de substrats sableux. Ainsi, si les abaissements améliorent indubitablement les conditions hydro-éco-morphologiques (i.e. la diversité des faciès d’écoulement), la restauration physique du lit fortement dégradé de l’Yerres se limite au rétablissement du transport du matériel de fond sableuxThe Yerres catchment (1030 km²) is located at the southeast border of the Paris conurbation and spreads on the low relief Brie Plateau. Topographical characteristics and geographical location provide the Yerres River with a very low gradient (0,009 %) and a high longitudinal partitioning (0,5 dam/km). Cross-structures are either ancient (medieval watermills) or more recent (mobile dams) and often associated with river channelling. Dam perturbation on sediment fluxes and bed morphological modifications have led to a significant degradation of the river fluvial dynamic and morphological diversity. In this context of a much artificialized low-energy river (< 10 W/m²), we aimed at assessing the efficiency of three mobile dam (h < 3 m) lowering on bed hydromorphological restoration. For that purpose, high spatial and temporal resolution monitoring of bed topography and sediment-size were carried out between 2015 and 2017, in order to document fluvial system adjustment to dam lowering through morphological and grain-size change. Before dam lowering, fine sediment had mainly deposited in channel margins forming mud banks, except for Ozouer impoundment (the more upstream study site). For the latter, sand sedimentation had been extended to the whole channel width. After dam lowering, it also experienced the more pronounced morphological change, characterised by significant bed erosion upstream and little bed aggradation downstream. However, morphological response to dam lowering remained moderate given the high discharges over the monitoring period. Channel adjustments also appeared to be linked to sand-bed. Thus, while dam lowering undoubtedly improve hydro-eco-morphological conditions (i.e. flow facies diversity), physical restoration of the highly degraded Yerres riverbed is restricted to the sand bed material transport restoration
Libros sobre el tema "Low-energy rivers":
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Shan, Shengdao. Chang san jiao di qu neng yuan yu di tan zhuan xing yan jiu: Research on energy and low carbon transition in Yangtze River Delta Region. 8a ed. Beijing: Ke xue chu ban she, 2013.
2
Rez, Peter. Electrical Power Generation: Hydroelectricity, Tides and Pumped Storage. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198802297.003.0008.
Resumen
Hydroelectricity already contributes to electrical supply in places where it can. What are needed are rivers with adequate flow that can be dammed to provide a significant vertical drop. These are usually found in mountainous regions where runoff from snowmelt provides adequate water supply. Renewables such as solar and wind have low power densities. That means large areas will be needed to meet the electrical energy needs of cities in developed countries. The other problem is that they do not supply power when it is needed. Energy can be stored by pumping water uphill into a reservoir at a higher elevation. All the energy needs of a desert city can be met with solar in places where every day is sunny. Low-density development means there is enough roof area, and there are elevation differences for pumped storage. There are not many places in the world that meet all these conditions.
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Jacobsen, Dean y Olivier Dangles. Ecology of High Altitude Waters. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198736868.001.0001.
Resumen
This book brings together current knowledge on patterns and processes in the ecology of streams, lakes, and wetlands situated at more than 3000 m above sea level. The alpine headwaters of the large Asian rivers and Lake Titicaca are both well-known and iconic examples. High altitude waters include more than these systems—they are both numerous and cover many habitat types, organisms, and specializations. The book provides an overview of the variety of aquatic ecosystems and habitats, their environmental features, prominent species, and their functional adaptations to the harsh aquatic environmental conditions through to global diversity patterns along altitudinal gradients, community dynamics, species interactions and dispersal, trophic relations, and energy flows. High altitude waters are ideal systems to address a broad range of topical themes in ecology because patterns and processes are both diverse and singular. The book highlights how key concepts in ecology (e.g. the stress gradient hypothesis, the biodiversity–ecosystem functioning relationship) could find relevant study models in high altitude waters. The usual perception of pristine mountain waters is far from true, particularly in the case of high altitude waters at low latitudes where human population density is often high, and local communities live in intimate contact with, utilize, influence, and exploit these aquatic systems. Climate change effects, extinction risks of mountain populations due to vanishing glaciers, multiple human impacts, management, and conservation are also treated thoroughly. The book is richly illustrated with diagrams and numerous pictures of these poorly known systems and species.
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Yang, Kun. Observed Regional Climate Change in Tibet over the Last Decades. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.587.
Resumen
The Tibetan Plateau (TP) is subjected to strong interactions among the atmosphere, hydrosphere, cryosphere, and biosphere. The Plateau exerts huge thermal forcing on the mid-troposphere over the mid-latitude of the Northern Hemisphere during spring and summer. This region also contains the headwaters of major rivers in Asia and provides a large portion of the water resources used for economic activities in adjacent regions. Since the beginning of the 1980s, the TP has undergone evident climate changes, with overall surface air warming and moistening, solar dimming, and decrease in wind speed. Surface warming, which depends on elevation and its horizontal pattern (warming in most of the TP but cooling in the westernmost TP), was consistent with glacial changes. Accompanying the warming was air moistening, with a sudden increase in precipitable water in 1998. Both triggered more deep clouds, which resulted in solar dimming. Surface wind speed declined from the 1970s and started to recover in 2002, as a result of atmospheric circulation adjustment caused by the differential surface warming between Asian high latitudes and low latitudes.The climate changes over the TP have changed energy and water cycles and has thus reshaped the local environment. Thermal forcing over the TP has weakened. The warming and decrease in wind speed lowered the Bowen ratio and has led to less surface sensible heating. Atmospheric radiative cooling has been enhanced, mainly through outgoing longwave emission from the warming planetary system and slightly enhanced solar radiation reflection. The trend in both energy terms has contributed to the weakening of thermal forcing over the Plateau. The water cycle has been significantly altered by the climate changes. The monsoon-impacted region (i.e., the southern and eastern regions of the TP) has received less precipitation, more evaporation, less soil moisture and less runoff, which has resulted in the general shrinkage of lakes and pools in this region, although glacier melt has increased. The region dominated by westerlies (i.e., central, northern and western regions of the TP) received more precipitation, more evaporation, more soil moisture and more runoff, which together with more glacier melt resulted in the general expansion of lakes in this region. The overall wetting in the TP is due to both the warmer and moister conditions at the surface, which increased convective available potential energy and may eventually depend on decadal variability of atmospheric circulations such as Atlantic Multi-decadal Oscillation and an intensified Siberian High. The drying process in the southern region is perhaps related to the expansion of Hadley circulation. All these processes have not been well understood.
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Ross, Andrew. Bird on Fire. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199828265.001.0001.
Resumen
Phoenix, Arizona is one of America's fastest growing metropolitan regions. It is also its least sustainable one, sprawling over a thousand square miles, with a population of four and a half million, minimal rainfall, scorching heat, and an insatiable appetite for unrestrained growth and unrestricted property rights. In Bird on Fire, eminent social and cultural analyst Andrew Ross focuses on the prospects for sustainability in Phoenix--a city in the bull's eye of global warming--and also the obstacles that stand in the way. Most authors writing on sustainable cities look at places like Portland, Seattle, and New York that have excellent public transit systems and relatively high density. But Ross contends that if we can't change the game in fast-growing, low-density cities like Phoenix, the whole movement has a major problem. Drawing on interviews with 200 influential residents--from state legislators, urban planners, developers, and green business advocates to civil rights champions, energy lobbyists, solar entrepreneurs, and community activists--Ross argues that if Phoenix is ever to become sustainable, it will occur more through political and social change than through technological fixes. Ross explains how Arizona's increasingly xenophobic immigration laws, science-denying legislature, and growth-at-all-costs business ethic have perpetuated social injustice and environmental degradation. But he also highlights the positive changes happening in Phoenix, in particular the Gila River Indian Community's successful struggle to win back its water rights, potentially shifting resources away from new housing developments to producing healthy local food for the people of the Phoenix Basin. Ross argues that this victory may serve as a new model for how green democracy can work, redressing the claims of those who have been aggrieved in a way that creates long-term benefits for all. Bird on Fire offers a compelling take on one of the pressing issues of our time--finding pathways to sustainability at a time when governments are dismally failing their responsibility to address climate change.
Capítulos de libros sobre el tema "Low-energy rivers":
1
Millar, Dean L. "Wave and tidal power". En Energy... beyond oil. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780199209965.003.0006.
Resumen
This chapter reviews how electricity can be generated from waves and tides. The UK is an excellent example, as the British Isles have rich wave and tidal resources. The technologies for converting wave power into electricity are easily categorized by location type. 1. Shoreline schemes. Shoreline Wave Energy Converters (WECs) are installed permanently on shorelines, from where the electricity is easily transmitted and may even meet local demands. They operate most continuously in locations with a low tidal range. A disadvantage is that less power is available compared to nearshore resources because energy is lost as waves reach the shore. 2. Nearshore schemes. Nearshore WECs are normally floating structures needing seafloor anchoring or inertial reaction points. The advantages over shoreline WECs are that the energy resource is much larger because nearshore WECs can access long-wavelength waves with greater swell, and the tidal range can be much larger. However, the electricity must be transmitted to the shore, thus raising costs. 3. Offshore schemes. Offshore WECs are typically floating structures that usually rely on inertial reaction points. Tidal range effects are insignificant and there is full access to the incident wave energy resource. However, electricity transmission is even more costly. Tidal power technologies fall into two fundamental categories:1. Barrage schemes. In locations with high tidal range a dam is constructed that creates a basin to impound large volumes of water. Water flows in and out of the basin on flood and ebb tides respectively, passing though high efficiency turbines or sluices or both. The power derives from the potential energy difference in water levels either side of the dam. 2. Tidal current turbines. Tidal current turbines (also known as free flow turbines) harness the kinetic energy of water flowing in rivers, estuaries, and oceans. The physical principles are analogous to wind turbines, allowing for the very different density, viscosity, compressibility, and chemistry of water compared to air. Waves are caused by winds, which in the open ocean are often of gale force (speed >14 m/s).
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Álvarez-Borrego, Saul. "Physical Oceanography". En Island Biogeography in the Sea of Cortés II. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195133462.003.0008.
Resumen
The nature of the relationships between physical and biological processes in the ocean is subtle and complex. Not only do the physical phenomena create a structure, such as a shallow, mixed layer or a front, within which biological processes may proceed, but they also influence the rates of biological processes in many indirect ways. In the ocean, physical phenomena control the distribution of nutrients necessary for phytoplankton photosynthesis. Places with higher kinetic energy have higher concentrations of planktonic organisms, and that makes the whole food web richer (Mann and Lazier 1996). For example, in the midriff region of the Sea of Cortés (Tiburón and Ángel de la Guarda; fig. 1.2), tidal currents are strong, and intense mixing occurs, creating a situation similar to constant upwelling. Thus, primary productivity is high, and this area supports large numbers of sea birds and marine mammals (Maluf 1983). The Gulf of California is a dynamic marginal sea of the Pacific Ocean and has been described as an area of great fertility since the time of early explorers. Gilbert and Allen (1943) described it as fabulously rich in marine life, with waters fairly teeming with multitudes of fish, and to maintain these large numbers, there must be correspondingly huge crops of their ultimate food, the phytoplankton. Topographically the gulf is divided into a series of basins and trenches, deepening to the south and separated from each other by transverse ridges (Shepard 1950; fig. 3.1). Input of nutrients into the gulf from rivers is low and has only local coastal effects. The Baja peninsula has only one, very small river, near 27°N; rivers in mainland Mexico and the Colorado River have dams that divert most of the water for agricultural and urban use. The gulf has three main natural fertilization mechanisms: wind-induced upwelling, tidal mixing, and thermohaline circulation. Upwelling occurs off the eastern coast with northwesterly winds (winter conditions from December through May) and off the Baja California coast with southeasterly winds (summer conditions from July through October), with June and November as transition periods (Álvarez-Borrego and Lara- Lara 1991).
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"Community Ecology of Stream Fishes: Concepts, Approaches, and Techniques". En Community Ecology of Stream Fishes: Concepts, Approaches, and Techniques, editado por Alexander S. Flecker, Peter B. McIntyre, Jonathan W. Moore, Jill T. Anderson, Brad W. Taylor y Robert O. Hall. American Fisheries Society, 2010. http://dx.doi.org/10.47886/9781934874141.ch28.
Resumen
<em>Abstract</em>.—Migratory fishes are common in freshwaters throughout the world and can fundamentally alter recipient ecosystems. We describe different types of fish migrations and consider their importance from the perspective of ecosystem subsidies—that is, landscape-scale flows of energy, materials, and organisms that are important in driving local food web and ecosystem dynamics. We distinguish between two general categories of subsidies, which we term here material subsidies and process subsidies. Material subsidies are the transfer of energy, nutrients, and other resources resulting in direct changes in resource pools within ecosystems. We posit that material subsidies occur under only a subset of life history strategies and ecological settings, and the potential for migratory fish to represent major material subsidies is greatest when (1) the biomass of migrants is high relative to recipient ecosystem size, (2) the availability of nutrients and energy is low in the recipient ecosystem (i.e., oligotrophic), and (3) there are effective mechanisms for both liberating nutrients and energy from migratory fishes and retaining those materials within the food web of the recipient ecosystem. Thus, anadromous semelparous Pacific salmon <em>Oncorhynchus </em>spp. with en masse programmed senescence in oligotrophic Pacific Northwest streams can be large material subsidies. In contrast, process subsidies arise from feeding or other activities of migratory species that directly affect process rates within recipient ecosystems. For example, the physical and chemical effects of grazing and sediment-feeding fishes such as prochilodontids, as well as seed dispersal by large-bodied frugivorous characins, represent potentially key process subsidies by migratory fishes in some of the great rivers of South America. We speculate that process subsidies are more widespread than material subsidies from migratory stream fishes because they are independent of the type of migration patterns, life history, and distance traveled. Nevertheless, the magnitude of process subsidies is likely to be greatest under a specific subset of ecological conditions, which can differ from those where material subsidies might be most important. In addition to migrant biomass, the potential for migratory fish to represent strong process subsidies is regulated by migrant interaction strength and the degree to which a migratory species is functionally unique in a particular ecological setting. Unlike material subsidies, which require high migrant biomass as conveyor belts of materials, migratory fishes can be crucial process subsidies, even when migrant biomass is low, if they are functionally unique and strong interactors. We provide specific examples of these different types of subsidies and outline key directions of research for furthering our understanding of the functional significance of migratory stream fishes. Our aim is to highlight the diversity of subsidies provided by migratory fishes in order to foster a more comprehensive perspective on fishes as essential components of riverine ecosystems.
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Bissett, Thaddeus G., Stephen B. Carmody y D. Shane Miller. "Investigations at the Barnes Site (40DV307)". En The Cumberland River Archaic of Middle Tennessee, 91–110. University Press of Florida, 2019. http://dx.doi.org/10.5744/florida/9781683400837.003.0006.
Resumen
At the Barnes Site (40DV307) along the Cumberland River, two discrete shell-bearing deposits dating to the Late Archaic and Middle Woodland periods (approximately 3500 and 1800 cal BP respectively) are separated by a thick Early Woodland–period shell-free stratum dated between 2900 and 2000 cal BP. Alternating shell-bearing and shell-free deposits at sites elsewhere in the southern Ohio Valley have often been viewed as indicative of long-term changes in subsistence practices and traditions or large-scale environmental fluctuations affecting resource abundance. At Barnes, however, chronological, geoarchaeology, and paleoethnobotany data from shell-bearing strata recovered in 2010 and 2012 suggest that the two shell-bearing deposits mark the locations of shellfish processing at or near the river’s edge when the river channel was physically closer to the current site location. Particle-size data indicate that when the shell-free deposit accumulated, the site was situated in a low-energy depositional zone, suggesting that the river channel had shifted further to the west during that period of time.
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Abelho, Manuela, Cristina Canhoto y Manuel A. S. Graça. "Sources of energy in low-order srteams". En Aquatic ecology of the Mondego River basin global importance of local experience, 231–42. Imprensa da Universidade de Coimbra, 2002. http://dx.doi.org/10.14195/978-989-26-0336-0_14.
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Smith, Derald G., Stephen M. Hubbard, Jason R. Lavigne, Dale A. Leckie y Milovan Fustic. "Stratigraphy of Counter-Point-Bar and Eddy-Accretion Deposits in Low-Energy Meander Belts of the Peace-Athabasca Delta, Northeast Alberta, Canada". En From River to Rock RecordThe preservation of fluvial sediments and their subsequent interpretation. SEPM Society for Sedimentary Geology, 2011. http://dx.doi.org/10.2110/sepmsp.097.143.
Actas de conferencias sobre el tema "Low-energy rivers":
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Wang, Juan, Yue Wang, Haizhen Yang, Zhibo Lu, Xiaotian Xu, Fangming Jin, Qi Zhou y Bing Wu. "Health evaluation indicator system for urban landscape rivers, case study of the Bailianjing River in Shanghai". En 2nd International Symposium on Aqua Science, Water Resource and Low Carbon Energy. AIP, 2010. http://dx.doi.org/10.1063/1.3529346.
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Calloway, Kevin y Terry Larson. "Resolution of Circulating Water Pump Problems Caused by Low River Levels at the Neal North Generating Station". En ASME 2004 Power Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/power2004-52075.
Resumen
Low winter water levels are causing reliability problems with once-through circulating water pump systems at several coal-fired power generating plants sited along the Missouri and Mississippi Rivers. River bottom degradation and potential COE river management changes make low river levels a likely on-going problem especially during drought years currently being experienced in the Midwest. This paper outlines circulating water pumping problems that have occurred at MidAmerican Energy’s Neal North Energy Center due to low water levels in the Missouri River, and the steps taken to resolve these problems. Remedial design solutions that were either considered or implemented, such as supplemental pumps, vacuum lift systems, suction scoops, a new river water intake, and converting to a closed-loop cooling tower system, will be discussed. An in-depth discussion will be made on the supplemental pump system installed in the fall of 2002 and currently in operation on the Unit 3 river intake. Applicable permitting requirements will also be discussed. The new supplemental pump system consists of six submersible axial flow pumps mounted on the front of the existing Unit 3 intake. The total flow capacity of the six supplemental pumps is around 220,000 gpm which is discharged into the existing intake to maintain an acceptable wet well water level for the existing circulating water pump to operate. Other system components include an overhead monorail system to facilitate annual supplemental pump installation/removal, a floating ice deflector system, and a warm-water discharge splash plate. The supplemental pumps are installed and operated during winter months when river levels are low, and removed during the river navigation season when the COE maintains higher river flows.
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Liang, Hao, Weiding Long, Yingqian Song y Fang Liu. "The Analysis and Application of Energy-Internet in the Low-Carbon Community". En ASME 2010 4th International Conference on Energy Sustainability. ASMEDC, 2010. http://dx.doi.org/10.1115/es2010-90338.
Resumen
The energy-Internet is a new energy supply method based on urban compact and densely populated community in a low-carbon city. The principle is to connect small energy generation stations and combined heat and power system (CHP) based on distributed energy technology and renewable energy into a network in the urban district. In this way, the cooling, heating and electricity could all back each other up. Each building of the community could collect the energy and then put that energy into the energy-internet to supply the heating and power to buildings. The power in the energy-internet could also be used for charging electric vehicles. So the energy use in the urban community would be basically self-sufficient. The energy generation stations in the energy-internet could be solar power, wind power, biomass cogeneration (including refuse power generation), household fuel cell, low-grade heat in rivers, lakes, urban sewage and soil. In this way, large-scale renewable energy and unused energy could be fully used and applied in a compact and dense community. If the energy-internet is suitable designed, the equipment capacity, energy consumption and CO2 emission of the community could be greatly reduced, energy efficiency could be optimized and improved and the heat island effect could also be alleviated. This article explores three major problems of the construction of energy internet and their solutions: namely, the location and layout of the energy station, the environmental economic dispatch model of the energy internet with power dispatching as an example, the optimal path design of hot water pipe network combined with graph theory and genetic algorithms.
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MOSIEJ, Józef y Teresa SUCHECKA. "THE ROLE OF IRRIGATION IN RIVER VALLEYS TO DEVELOP WATER QUALITY, PRODUCTION OF BIOMASS AND SUSTAINABLE RURAL DEVELOPMENT - CASE STUDY". En RURAL DEVELOPMENT. Aleksandras Stulginskis University, 2018. http://dx.doi.org/10.15544/rd.2017.076.
Resumen
Ner river and its valley for over 170 years has been receiver for sewages from the city of Łódź. The natural system of this region (on the border of the watershed location, limitations of water supplies sources, lack of bigger natural rivers) in connection to city growth, lead to forming of specific system involving an agglomeration and water supplies system as well as wastewaters utilization system. The Ner river valley has the great potential to be effective in production biomass for energy purposes. Irrigation with polluted Ner river water cover fast growing plants high water and nutritional requirements. This would also work for the improvement of Ner river water quality. The achievement of good quality of water is not possible without irrigation of agricultural land in river valley. An amount of sewage discharged to Ner (193,017 m³ per day) several times higher then its natural flow in river. This is a result of strategy of water supply that is supported by transfer of water from Pilica river and underground water uptake for agglomeration. Relatively high runoff coefficient in years 1952 – 2011 was equal to 0.325 for Ner, in comparison to 0.17 for other rivers in Warta watershed. Despite the low natural flow Ner river discharges annually relatively high contaminants’ load to Warta river. In the analysed period (1995-2003) the annual average flow of Ner river amounted 10 % of annual average Warta river flow below its estuary. The share of analysed indicators of contaminants’ load approximated 27 % for total nitrogen, 37 % for phosphorus, 39 % for BOD5 and 28% for suspended solids. In the period 2004-2011 the annual average flow of Ner river amounted 13.8 % of annual average Warta river flow. The share of investigated pollutants loads consists 27.9 % for total nitrogen, 42.6 % for phosphorus, 19.8 % for BOD5 and 19.6 % for suspended solids.
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Ip, Peggy P., Sammy Houssainy y H. Pirouz Kavehpour. "Modeling of a Low Cost Thermal Energy Storage System to Enhance Generation From Small Hydropower Systems". En ASME 2017 Power Conference Joint With ICOPE-17 collocated with the ASME 2017 11th International Conference on Energy Sustainability, the ASME 2017 15th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2017 Nuclear Forum. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/power-icope2017-3684.
Resumen
Undeveloped small hydropower generation sites are abundant throughout the water conveyance infrastructure and natural rivers in the United States. Due to its small scale, micro-hydro development requires substantial upfront capital costs, maintenance and operation costs for customized engineering and construction. The significant investments required for developing small hydropower are inhibiting for utilities, residential and commercial users to adopt. An inexpensive energy storage system and a well-designed power controls system can be integrated with small hydropower sites to increase its cost-effectiveness and reliability. This paper introduces the concept of storing low-power generated from small hydro turbines during long off-peak periods and dispatching at high-power as grid-quality electricity during peak periods. The use of an ultra-low cost thermal energy storage (ULCTES) system is examined. Boosting the power output for small hydro generation allows commercial users to avoid significant demand charges during operation, making small hydro an attractive cost saving strategy and therefore breaking down the cost barrier. The ULCTES operates much like a bulk power production unit and a peaker plant, in which it is capable of dispatching constant power over a long period during peak periods when conventional sources are unavailable. Improvements in system reliability and economic value are evaluated using microgrid optimization software HOMER Energy. In particular, two cases are studied with variations in types of end users and energy management goals. Energy costs savings, demand charges savings and renewable energy penetration are determined. Distributed energy storage systems are shown to reduce energy costs and increase the renewable energy penetration for commercial users. With ULCTES, microgrids have the flexibility to manage fluctuating renewable energy generation as well as respond to rapidly changing loads on a daily basis. A larger hydroelectricity system is shown to be more feasible with distributed energy storage systems for isolated users without any connection to the grid.
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Rohmer, Julien, Dominique Knittel, Guy Sturtzer, Damien Flieller y Jean Renaud. "Small Hydro Plant Using Archimedes Screw: Modeling and Analysis". En ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-37895.
Resumen
In this paper we introduce a small hydro plant that uses Archimedes screws. This is an alternate solution to small-scale hydropower as it exploits unused resources such as small rivers or streams. Based on hydrological study, we developped a theoretical static model to estimate the annual energy production depending on flow rate, hydrostatic head and Archimedes screw efficiency variations. Then, we studied the flood and low-water periods in order to exclude harmful climatic events of the annual energy production estimation, used for the Archimedes screw design.
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Nalbandian, Rozina N., Karen U. Girgis, Benjamin T. Kong, Ulyses Aguirre, Adrian Gil C. Victorio, Justin Andrew Lee y Reza Baghaei Lakeh. "Simulation of an ROC-Based Thermal Energy Storage System in Charge and Discharge Cycles". En ASME 2021 15th International Conference on Energy Sustainability collocated with the ASME 2021 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/es2021-63930.
Resumen
Abstract In this paper, Computational Fluid Dynamics (CFD) is employed to investigate the heat transfer characteristics of Reverse Osmosis Concentrate (ROC) as an alternative, low-cost thermal energy storage medium. Thermal energy storage is a critical component for increasing efficiency and dispatchability of solar thermal and combined heat and power plants. The byproduct of water desalination, ROC, is classified as an industrial waste by the U.S. Environmental Protection Agency as it has negative effects on vegetation and sea-life. Currently, ROC disposal includes deep-well injection, surface discharge to rivers, discharge to the ocean, and evaporation ponds. The composition and thermal properties of ROC salt vary depending on the original source of feedwater. Transient models are utilized to understand the heat transfer between the heat transfer fluid and storage fluid (i.e., ROC) over time. This simulation also provides valuable information in determining the optimal operating conditions of the thermal energy storage system. This information will be used in conjunction with a cost analysis, focused on the transportation, processing and containment cost of the energy storage, that aims to determine the economic feasibility of ROC technology in large scale, commercial applications.
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Rivera, Marcos, Daniel Shook y Emine Foust. "Experimental and Numerical Investigation Into Vertical Axis Water Turbine Self-Starting Phenomenon". En ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-23031.
Resumen
Abstract In rural areas and isolated regions of the world, it is often difficult to obtain reliable access to electricity. A solution often exploited is the use of diesel generators to power homes but that has its negative effects on climate change. In this study, an alternative solution is being investigated, which involves the use of water turbines. For low head applications such as rivers, hydrokinetic turbines are used to harness the kinetic energy in rivers. There are two types of hydrokinetic turbines: horizontal and vertical axis water turbines. The turbine studied in this paper is the Darrieus type vertical axis water turbine (VAWT) which has three straight blades. Darrieus type VAWT primarily use lift forces to operate. Advantages of vertical axis water turbines are simple construction, low cost, and being able to self-orient. However, the Darrieus VAWT has several disadvantages like self-starting problem, low coefficient of performance, shaking, debris accumulation, and cavitation. In this study, the effect of using thermoplastic polyurethane blades with varying levels of flexibility have been investigated to remedy the self-starting problem. For blade profile, S1046 airfoil is selected. 3-D numerical models were created by using time-accurate Reynolds-averaged Navier Stokes (RANS) commercial solver (ANSYS Fluent 2019 R3). Experimental results show that turbine with lower blade hardness starts to rotate at 0.34m/s while the turbine with higher blade hardness experiences rotation at 0.51m/s.
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Hobeck, Jared D. y Daniel J. Inman. "Energy Harvesting From Turbulence-Induced Vibration in Air Flow: Artificial Piezoelectric Grass Concept". En ASME 2011 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2011. http://dx.doi.org/10.1115/smasis2011-5053.
Resumen
Turbulence-induced vibration is generally considered undesirable, and is a phenomenon that if not properly anticipated can lead to catastrophic structural failure. From an energy harvesting perspective however, these types of vibrations have been found to be quite valuable. Turbulence can greatly diminish the performance of traditional fluid flow energy harvesting devices such as turbine, or propeller type designs. Even more recently developed nontraditional harvesters that take advantage of vortex shedding, flutter, or related phenomena in fluid dynamics become extremely inefficient, and in some cases, completely fail to generate useful power in turbulent flow. Motivation for this work comes from the fact that very little research has been done on methods for harvesting energy from turbulence. The primary objective of this research is to design and develop a deploy-and-forget energy harvesting device for use in low velocity (∼0.5 m/s) highly turbulent water flow environments i.e. small rivers and streams. The work presented here focuses on a novel, lightweight, highly robust, energy harvester design referred to as “piezoelectric grass”. This biologically inspired design consists of an array of cantilevers, each constructed with piezoelectric material. When exposed to proper turbulent flow conditions, these cantilevers vibrate vigorously due to rapidly varying pressure fields along their faces. Electrical power is generated directly from these vibrations via the piezoelectric effect. Small-scale wind tunnel tests were carried out to validate the concept. Included in this paper are the results of a direct comparative study performed on two types of harvesters in air. The generating elements or “blades of grass” of one design are made of PVDF cantilevers (type-1), and those of the other design are made with PZT QuickPacks™ mounted to the base of spring steel cantilevers (type-2). Results from these tests show very clearly that optimum harvesting conditions exist. The maximum power output per cantilever was ∼1μW for the type-1 harvester, and increased up to ∼ 1mW for the type-2 harvester which is among the highest found in literature for similar harvesting methods.
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Umehara, Akira, Akira Umehara, Satoshi Asaoka, Satoshi Asaoka, Naoki Fujii, Naoki Fujii, Sosuke Otani et al. "ENERGY TRANSFER EFFICIENCIES ON LOWER TROPHIC LEVELS WITH INTENSIVE OYSTER FARMING IN HIROSHIMA BAY, JAPAN". En Managing risks to coastal regions and communities in a changing world. Academus Publishing, 2017. http://dx.doi.org/10.21610/conferencearticle_58b43169dc569.
Resumen
In enclosed water areas, organic matters are actively produced by phytoplankton due to abundant nutrient supply from the rivers. In our study area of the semi-enclosed Hiroshima Bay, oyster farming consuming high primary production has been developed since the 1950s, and the oyster production of Hiroshima prefecture have had the largest market share (ca. 60%) in Japan. In this study, species composition of phytoplankton, primary production, and secondary production of net zooplanktons and oysters were determined seasonally at seven stations in the bay between November 2014 and August 2015. In the bay, diatoms including Skeletonema costatum dominated during the period of the study. The primary productions markedly increased during summer (August), and its mean values in the northern part of the bay (NB) and the southern part (SB) were 530 and 313 mgC/m2/d, respectively. The productions of net zooplankton and oyster increased during the warm season, and its mean values in the NB were 14 and 1.2 mgC/m2/d, and in SB were 28 and 0.9 mgC/m2/d, respectively. The energy transfer efficiencies from the primary producers to the secondary producers in the NB and SB were 2.8% and 9.1%, respectively. However, the transfer efficiency to the oysters was approximately 0.3% in the bay. This study clearly showed the spatial difference of the productions and transfer efficiencies, and the low contribution of the production of oysters in secondary productions in Hiroshima Bay.
Informes sobre el tema "Low-energy rivers":
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Bernitsas, Michael B. y Tad Dritz. Low Head, Vortex Induced Vibrations River Energy Converter. Office of Scientific and Technical Information (OSTI), junio de 2006. http://dx.doi.org/10.2172/896401.
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Rine, Kristin, Roger Christopherson y Jason Ransom. Harlequin duck (Histrionicus histrionicus) occurrence and habitat selection in North Cascades National Park Service Complex, Washington. National Park Service, abril de 2022. http://dx.doi.org/10.36967/nrr-2293127.
Resumen
Harlequin ducks (Histrionicus histrionicus) are sea ducks that migrate inland each spring to nest along fast-flowing mountain streams. They are considered one of the most imperiled duck species in North America and occur in two distinct populations on the Atlantic and Pacific coasts. The Pacific coast population includes Washington State, where harlequin ducks breed in the Olympic, Cascade, and Selkirk Mountains. This species is designated as a Management Priority Species by the National Park Service within North Cascades National Park Service Complex (NOCA). This report summarizes harlequin duck surveys conducted during 15 years across a 27-year period (1990 and 2017) on major streams within NOCA, and incidental observations collected from 1968–2021. The primary objectives of these surveys were to 1) document the distribution and abundance of harlequin duck observations within NOCA boundaries, 2) describe productivity (number of broods and brood size), 3) describe breeding chronology of harlequin ducks, and 4) describe habitat characteristics of breeding streams. Sixty-eight stream surveys over 15 years resulted in observations of 623 individual harlequin ducks comprising various demographics, including single adults, pairs, and broods. In addition, we collected 184 incidental observations of harlequin ducks from visitors and staff between 1968–2021. Harlequin ducks were observed on 22 separate second- to sixth-order streams throughout NOCA across the entire 53-year span of data, both incidentally and during harlequin duck surveys by Park staff. Harlequin ducks were detected on 8 of the 13 streams that were actively surveyed. Excluding recounts, 88.7% (n = 330) of individual harlequin duck observations during surveys occurred in the Stehekin River drainage. Between all surveys and incidental observations, 135 unpaired females without broods were sighted across all NOCA waterways. Thirty-nine broods were recorded between NOCA surveys and incidental observations, with a mean brood size of 3.61 (± 1.44 SD; range = 2–10). Breeding pairs were recorded as early as April 5 and were seen on streams until June 15, a period of less than seven weeks (median: May 2), but most pairs were observed within a 3-week span, between April 26 and May 17. Single females (unpaired with a male, with (an)other female(s), or with a brood) were observed on streams between April 26 and August 25 (median: July 3), though most observations were made within a 5-week period between June 12 and July 19. Habitat data collected at adult harlequin duck observation sites indicate that the birds often used stream reaches with features that are characteristic of high-energy running water. While adults occupied all instream habitat types identified, non-braided rapids and riffles were used most frequently, followed by pools and backwaters. Larger instream substrate sizes (cobbles and boulders) were present at most observation sites. Adult harlequin ducks were more often found at locations that lacked visible drifting or lodged woody debris, but drift debris was a slightly more abundant debris type. The presence of gravel bars and at least one loafing site was common. Adult harlequin ducks were more often observed in association with vegetation that offered some cover over the channel, but not where banks were undercut. The average channel width at adult observation sites was 34.0 m (range: 6-80 m; n = 114) and 27.6 m (± 15.7 m; range: 10-60 m; n = 12) at brood observation sites. Compared to adult harlequin duck sites, broods were observed more frequently in low velocity habitat (pools, backwaters), but rarely in rapids. Cobble and boulder substrates were still the most dominant substrate type. Contrary to adult ducks, broods were observed most often observed in meandering stream channels, a morphology indicative of low gradient, low velocity stream reaches. Most broods were observed in stream reaches with gravel bars, loafing sites, and...