عملیاتی عمرانی که سالی یکبار توریستها را به رود زرد چین میکشاند
تصویری که میبینید، عملیات شنشویی سد ذخیره ژیائولنگدی (Xiaolangdi) در استان هنان چین را نشان میدهد که روی رود زرد بنا شده است. این سد که ساخت آن ۳.۵ میلیارد دلار آمریکا هزینه برداشته، ۱۵۴متر ارتفاع و ۱۳۱۷ متر عرض دارد و ظرفیت تولید برق آن ۱۸۳۶ مگاوات است.
انباشته شدن گل و لای و رسوبات مختلف در بستر رودخانه عظیم زرد باعث کند شدن جریان آب و بالا آمدن سطح آب میشود که هر دو خطر وقوع سیل را افزایش میدهند. به همین دلیل، هر سال یک بار مسوولان سد در عملیاتی هماهنگ شده، دریچههای اضطراری سد را باز میکنند تا جریان شدید آب، گل و لای و رسوبات پاییندست رود را بشوید. هر سال بیش از ۳۰ میلیون تن گل و لای به این روش شسته میشود و بهطور متوسط ۲۰۳ سانتیمتر از ارتفاع بستر رودخانه در پاییندست میکاهد.
This is an illustration of water in our Solar System through time from before the Sun's birth through the creation of the planets. Image courtesy Bill Saxton, NSF/AUI/NRAO
Water was crucial to the rise of life on Earth and is also important to evaluating the possibility of life on other planets. Identifying the original source of Earth's water is key to understanding how life-fostering environments come into being and how likely they are to be found elsewhere.
New work from a team including Carnegie's Conel Alexander found that much of our Solar System's water likely originated as ices that formed in interstellar space. Their work is published in Science.
Water is found throughout our Solar System. Not just on Earth, but on icy comets and moons, and in the shadowed basins of Mercury. Water has been found included in mineral samples from meteorites, the Moon, and Mars.
Comets and asteroids in particular, being primitive objects, provide a natural "time capsule" of the conditions during the early days of our Solar System. Their ices can tell scientists about the ice that encircled the Sun after its birth, the origin of which was an unanswered question until now.
In its youth, the Sun was surrounded by a protoplanetary disk, the so-called solar nebula, from which the planets were born. But it was unclear to researchers whether the ice in this disk originated from the Sun's own parental interstellar molecular cloud, from which it was created, or whether this interstellar water had been destroyed and was re-formed by the chemical reactions taking place in the solar nebula.
"Why this is important? If water in the early Solar System was primarily inherited as ice from interstellar space, then it is likely that similar ices, along with the prebiotic organic matter that they contain, are abundant in most or all protoplanetary disks around forming stars," Alexander explained.
"But if the early Solar System's water was largely the result of local chemical processing during the Sun's birth, then it is possible that the abundance of water varies considerably in forming planetary systems, which would obviously have implications for the potential for the emergence of life elsewhere."
In studying the history of our Solar System's ices, the team-led by L. Ilsedore Cleeves from the University of Michigan-focused on hydrogen and its heavier isotope deuterium.
Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons. The difference in masses between isotopes results in subtle differences in their behavior during chemical reactions. As a result, the ratio of hydrogen to deuterium in water molecules can tell scientists about the conditions under which the molecules formed.
For example, interstellar water-ice has a high ratio of deuterium to hydrogen because of the very low temperatures at which it forms. Until now, it was unknown how much of this deuterium enrichment was removed by chemical processing during the Sun's birth, or how much deuterium-rich water-ice the newborn Solar System was capable of producing on its own.
So the team created models that simulated a protoplanetary disk in which all the deuterium from space ice has already been eliminated by chemical processing, and the system has to start over "from scratch" at producing ice with deuterium in it during a million-year period.
They did this in order to see if the system can reach the ratios of deuterium to hydrogen that are found in meteorite samples, Earth's ocean water, and "time capsule" comets. They found that it could not do so, which told them that at least some of the water in our own Solar System has an origin in interstellar space and pre-dates the birth of the Sun.
"Our findings show that a significant fraction of our Solar System's water, the most-fundamental ingredient to fostering life, is older than the Sun, which indicates that abundant, organic-rich interstellar ices should probably be found in all young planetary systems," Alexander said.
This package will install HEC-GeoRAS 10.1 and all its pre-requisites automatically. Documentation is available from the programs Help menu
ArcGIS 10.1 (ArcView license) with the 3D Analyst and Spatial Analyst extensions are required
Release Notes: The Animation Tool was not migrated to HEC-GeoRAS 10.1. The native ArcGIS Animation Toolbar must be used
Important note for HEC-GeoHMS 10.1 users
If you previously had HEC-GeoRAS 10.1 installed and want to use HEC-GeoHMS 10.1, you must uninstall the old version of HEC-GeoRAS 10.1 released in Feb 2013 and install the updated setup package below that supports side by side installation with HEC-GeoHMS 10.1
Download HEC-GeoRAS 10.1 [Updated] Install Package 12.7 MB
Researchers from the University of Southampton and the Australian National University report that sea-level rise since the industrial revolution has been fast by natural standards and - at current rates - may reach 80cm above the modern level by 2100 and 2.5 metres by 2200.
The team used geological evidence of the past few million years to derive a background pattern of natural sea-level rise. This was compared with historical tide-gauge and satellite observations of sea-level change for the 'global warming' period, since the industrial revolution. The study, which was funded by the Natural Environment Research Council (iGlass consortium) and Australian Research Council (Laureate Fellowship), is published in the journal Scientific Reports.
Lead author Professor Eelco Rohling, from the Australian National University and formerly of the University of Southampton, says: "Our natural background pattern from geological evidence should not be confused with a model-based prediction. It instead uses data to illustrate how fast sea level might change if only normal, natural processes were at work. There is no speculation about any new mechanisms that might develop due to man-made global warming. Put simply, we consider purely what nature has done before, and therefore could do again."
Co-author Dr Gavin Foster, a Reader in Ocean and Earth Science at the University of Southampton, who is based at the National Oceanography Centre, Southampton (NOCS), explains: "Geological data showed that sea level would likely rise by nine metres or more as the climate system adjusts to today's greenhouse effect. But the timescale for this was unclear. So we studied past rates and timescales of sea-level rise, and used these to determine the natural background pattern."
Co-author Dr Ivan Haigh, lecturer in coastal oceanography at the University of Southampton and also based at NOCS, adds: "Historical observations show a rising sea level from about 1800 as sea water warmed up and melt water from glaciers and ice fields flowed into the oceans. Around 2000, sea level was rising by about three mm per year. That may sound slow, but it produces a significant change over time."
The natural background pattern allowed the team to see whether recent sea-level changes are exceptional or within the normal range, and whether they are faster, equal, or slower than natural changes.
Professor Rohling concludes: "For the first time, we can see that the modern sea-level rise is quite fast by natural standards. Based on our natural background pattern, only about half the observed sea-level rise would be expected.
"Although fast, the observed rise still is (just) within the 'natural range'. While we are within this range, our current understanding of ice-mass loss is adequate. Continued monitoring of future sea-level rise will show if and when it goes outside the natural range. If that happens, then this means that our current understanding falls short, potentially with severe consequences."
پروفسور حسين صدقي اولين فرد ايراني است كه دكتراي تخصصي در رشته هيدرولوژي دريافت نموده است و اولین کتاب هیدرولوژی فارسی با عنوان مقدمه ای بر هیدرولوژی توسط این بزرگوار به رشته تحریر در آمده است. ايشان براي اخذ درجه دكترا در فرانسه تحصيل كرده اند و دوره فرصت مطالعاتي را در آمريكا گذرانده اند و لذا به زبانهاي فرانسه و انگليسي مسلط مي باشند. بدون اغراق ايشان يكي از بهترين هيدرولوژيست هاي دنيا مي باشند و ازمفاخر علمي ايران زمين و از چهره هاي ماندگار علمي به حساب مي آيند. ايشان علاوه بر مقام والاي علمي از نظر اخلاقي نيز در مرتبه اي بسيار بالا و بي نظير قرار دارند و يك معلم اخلاق واقعي مي باشند. حسن خلق، متانت، صبر، فروتني، برخورد بسيار محترمانه با ديگران در كنار سطح علمي بالا، از ايشان انساني بسيار دوست داشتني ساخته است. براي ايشان طول عمر با عزت از درگاه پروردگارخواستاریم. ايشان داراي یک پايگاه اينترنتي شخصي مي باشند. آدرس پايگاه علمي ايشان به شرح زير است:
ايشان همچنين يك پايگاه اينترنتي ادبي نيز دارند كه آدرس آن به شرح زير مي باشد:
This text integrates a wide range of research and tidal resource theory and data to present a detailed analysis of the physics and oceanography of tidal stream power devices together with a world wide resource analysis. Clearly structured throughout the book is divided into two distinct parts
Part One provides the theoretical background to the subject and deals with the historical development of the harmonic method for the synthesis of tidal currents; the principles of fluid and tidal flow and the principles of device ducts, turbines and electrical systems. A review and analysis of more than forty tidal stream power proposals is also discussed
Part Two provides a comprehensive overview of current practice. The economic modelling of tidal stream power installations is covered with more than three hundred current meter records from around the world used to analyse the potential and cost of tidal stream power on a global basis
reviews the tidal resources around the world
complete analysis of tidal stream power systems
includes historical information on tidal science and biographical information on major figures
concentrates on engineering physical geography rather than engineering specifics
includes a website with a wide range of computer models, data and simulations
برترین های نشریات ISI از لحاظ Impact Factor در موضوعات آب ، سازه هیدرولیکی ، سواحل و سازه های دریایی ، هیدرولیک و هیدرولوژی
ACI structural journal
China ocean engineering
Coastal engineering journal
Cold regions science and technology
Ingeniería hidráulica en México
International journal of offshore and polar engineering
Journal of hydraulic research
Journal of hydrology
J WATER SUPPLY REST
Proceedings of the Institution of Civil Engineers. Water management
Data-driven tools cast geographical patterns of rainfall extremes in new light
The globe shows rainfall values and represents research focused on global climate change while the India map shows the spatial variability of rainfall extremes.
Using statistical analysis methods to examine rainfall extremes in India, a team of researchers has made a discovery that resolves an ongoing debate in published findings and offers new insights. The study, initiated by Auroop Ganguly and colleagues at Oak Ridge National Laboratory, reports no evidence for uniformly increasing trends in rainfall extremes averaged over the entire Indian region.
It does, however, find a steady and significant increase in the spatial variability of rainfall extremes over the region.
These findings, published in Nature Climate Change, are contrary to results of some earlier work on this subject. The new study uses statistical methods designed explicitly for modeling extreme values and associated uncertainties.
"Our research suggests that one needs to be aware of the different characterizations of extremes and that these characterizations require both interpretability and statistical rigor," said Ganguly, now a faculty member at Northeastern University in Boston.
Ganguly and co-authors Subimal Ghosh (Indian Institute of Technology Bombay, Debasish Das (Temple University) and Shih-Chieh Kao (ORNL) used their statistical methodologies to analyze data from 1,803 stations from 1951 to 2003. This information was provided in 1-by-1-degree spatial grids by the India Meteorological Department.
The research team noted that statistical observations offer complementary insights compared to the current generation of physics-based computational models. This is especially the case if the goal is to understand climate and rainfall variability at local to regional scales.
Understanding climate model-simulated trends of precipitation extremes and developing metrics relevant for water resources decisions were the focus of a paper published earlier this year in the Journal of Geophysical Research.
In that paper, Ganguly and co-author Kao showed that while models provide relatively credible predictive insights of precipitation extremes at aggregate spatial scales, the uncertainty begins to increase significantly at localized spatial scales - especially over the tropical regions.
"Even as higher resolution models are attempting to get to the stage where spatially explicit insights can be generated, the kind of insights generated from observations in this study can be used as methods for model diagnostics and can help address science gaps," Kao said.
Ganguly noted that the Nature Climate Change paper, titled "Lack of uniform trends but increasing spatial variability in observed Indian rainfall extremes," is the result of a team effort with researchers from diverse disciplines.
Ghosh, the first author, is a hydro-climate scientist and civil engineer; Das is a graduate student in computer science and data mining; Kao is a statistical who specializes in water availability and flood frequency analysis; and Ganguly, a civil engineer, specializes in climate extremes and water sustainability as well as data sciences for complex systems.
This research concept was initiated when all the authors were working with Ganguly at ORNL and was funded by the Laboratory Directed Research and Development program. The National Science Foundation's Expeditions in Computing program and the Department of Science and Technology of India also provided funding.