Misplaced Pages

#975024

47-448: The current phase (IHP VIII: 2014–2021) is titled Water Security Responses to Regional and Global Challenges (2014-2021), and it is based on the principle of continuity with change, building on lessons and results from earlier phases of the program. It continues to promote and lead international hydrological research, facilitate education and capacity development and enhance governance in water resources management . The aim of these efforts

94-461: A line source or area source , such as surface runoff . Since the 1960s rather complex mathematical models have been developed, facilitated by the availability of high-speed computers. The most common pollutant classes analyzed are nutrients , pesticides , total dissolved solids and sediment . Physical geography Physical geography (also known as physiography ) is one of the three main branches of geography . Physical geography

141-435: A piezometer . Aquifers are also described in terms of hydraulic conductivity, storativity and transmissivity. There are a number of geophysical methods for characterizing aquifers. There are also problems in characterizing the vadose zone (unsaturated zone). Infiltration is the process by which water enters the soil. Some of the water is absorbed, and the rest percolates down to the water table . The infiltration capacity,

188-514: A "principle of comprehensive analysis of the territory" and "Russian Chernozem ". In the latter, he introduced the geographical concept of soil, as distinct from a simple geological stratum, and thus found a new geographic area of study: pedology . Climatology also received a strong boost from the Russian school by Wladimir Köppen whose main contribution, climate classification, is still valid today. However, this great geographer also contributed to

235-406: A major development. Some of his disciples made significant contributions to various branches of physical geography such as Curtis Marbut and his invaluable legacy for Pedology, Mark Jefferson , Isaiah Bowman , among others. The compilation of Edrisi marks an era in the history of science . Not only is its historical information most interesting and valuable, but its descriptions of many parts of

282-402: A more global approach to the understanding of the behavior of hydrologic systems to make better predictions and to face the major challenges in water resources management. Water movement is a significant means by which other materials, such as soil, gravel, boulders or pollutants, are transported from place to place. Initial input to receiving waters may arise from a point source discharge or

329-451: A prediction in practical applications. Ground water is water beneath Earth's surface, often pumped for drinking water. Groundwater hydrology ( hydrogeology ) considers quantifying groundwater flow and solute transport. Problems in describing the saturated zone include the characterization of aquifers in terms of flow direction, groundwater pressure and, by inference, groundwater depth (see: aquifer test ). Measurements here can be made using

376-402: Is affected by the interaction of dissolved oxygen with organic material and various chemical transformations that may take place. Measurements of water quality may involve either in-situ methods, in which analyses take place on-site, often automatically, and laboratory-based analyses and may include microbiological analysis . Observations of hydrologic processes are used to make predictions of

423-769: Is an important part of the water cycle. It is partly affected by humidity, which can be measured by a sling psychrometer . It is also affected by the presence of snow, hail, and ice and can relate to dew, mist and fog. Hydrology considers evaporation of various forms: from water surfaces; as transpiration from plant surfaces in natural and agronomic ecosystems. Direct measurement of evaporation can be obtained using Simon's evaporation pan . Detailed studies of evaporation involve boundary layer considerations as well as momentum, heat flux, and energy budgets. Remote sensing of hydrologic processes can provide information on locations where in situ sensors may be unavailable or sparse. It also enables observations over large spatial extents. Many of

470-468: Is another mountain lift and the cycle continues. Although Davis's theory is not entirely accurate, it was absolutely revolutionary and unique in its time and helped to modernize and create a geography subfield of geomorphology . Its implications prompted a myriad of research in various branches of physical geography. In the case of the Paleogeography, this theory provided a model for understanding

517-436: Is composed of 36 UNESCO Member States elected by UNESCO's General Conference at its ordinary sessions every two years. Each of UNESCO's six electoral regions elects Member States for membership in the council. The term lasts four years, and members are eligible for immediate re-election. For continuity, only half of the current Council members are elected each second year for the four-year period, so that in each biennium only half

SECTION 10

#1732791339976

564-489: Is only one of many important aspects within those fields. Hydrological research can inform environmental engineering, policy , and planning . Hydrology has been subject to investigation and engineering for millennia. Ancient Egyptians were one of the first to employ hydrology in their engineering and agriculture, inventing a form of water management known as basin irrigation. Mesopotamian towns were protected from flooding with high earthen walls. Aqueducts were built by

611-677: Is the International Groundwater Resources Assessment Centre (IGRAC) established in 2003. IGRAC works to facilitate sustainable groundwater resources across the world. They are based in the Netherlands. Youssef Filali-Meknassi  [ fr ] (2019–2020) Blanca Elena Jiménez Cisneros  [ es ] (2012–2018) Hydrological Hydrology (from Ancient Greek ὕδωρ ( húdōr )  'water' and -λογία ( -logía )  'study of')

658-688: Is the branch of natural science which deals with the processes and patterns in the natural environment such as the atmosphere , hydrosphere , biosphere , and geosphere . This focus is in contrast with the branch of human geography , which focuses on the built environment , and technical geography , which focuses on using, studying, and creating tools to obtain, analyze, interpret, and understand spatial information. The three branches have significant overlap, however. Physical geography can be divided into several branches or related fields, as follows: Main category: Geography Journals Mental geography and earth science journals communicate and document

705-753: Is the network of National Committees. They are fundamental to ensuring the widest possible participation of Member States in IHP programs. The committees are run under the authority of National Governments and are responsible for implementing IHP initiatives. Several working groups have been developed under the umbrella of the International Hydrological Programme as the UNESCO Land Subsidence International Initiative, LASII (former UNESCO Working Group on Land Subsidence ). Another initiative

752-916: Is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle , water resources , and drainage basin sustainability. A practitioner of hydrology is called a hydrologist . Hydrologists are scientists studying earth or environmental science , civil or environmental engineering , and physical geography . Using various analytical methods and scientific techniques, they collect and analyze data to help solve water related problems such as environmental preservation , natural disasters , and water management . Hydrology subdivides into surface water hydrology, groundwater hydrology ( hydrogeology ), and marine hydrology. Domains of hydrology include hydrometeorology , surface hydrology , hydrogeology , drainage-basin management, and water quality . Oceanography and meteorology are not included because water

799-580: Is thought of as starting at the land-atmosphere boundary and so it is important to have adequate knowledge of both precipitation and evaporation. Precipitation can be measured in various ways: disdrometer for precipitation characteristics at a fine time scale; radar for cloud properties, rain rate estimation, hail and snow detection; rain gauge for routine accurate measurements of rain and snowfall; satellite for rainy area identification, rain rate estimation, land-cover/land-use, and soil moisture, snow cover or snow water equivalent for example. Evaporation

846-502: Is to help meet the UN Millennium Development Goals on environmental sustainability , water supply , sanitation , food security and poverty alleviation . The results of this phase aim to be practical so both scientific communities and civil societies can apply and benefit from them. The IHP Intergovernmental Council is responsible for defining priorities and supervising execution of IHP. The council

893-513: Is utilized to formulate operating rules for large dams forming part of systems which include agricultural, industrial and residential demands. Hydrological models are simplified, conceptual representations of a part of the hydrologic cycle. They are primarily used for hydrological prediction and for understanding hydrological processes, within the general field of scientific modeling . Two major types of hydrological models can be distinguished: Recent research in hydrological modeling tries to have

940-637: The Greeks and Romans , while history shows that the Chinese built irrigation and flood control works. The ancient Sinhalese used hydrology to build complex irrigation works in Sri Lanka , also known for the invention of the Valve Pit which allowed construction of large reservoirs, anicuts and canals which still function. Marcus Vitruvius , in the first century BC, described a philosophical theory of

987-399: The return period of such events. Other quantities of interest include the average flow in a river, in a year or by season. These estimates are important for engineers and economists so that proper risk analysis can be performed to influence investment decisions in future infrastructure and to determine the yield reliability characteristics of water supply systems. Statistical information

SECTION 20

#1732791339976

1034-455: The 20th century, while governmental agencies began their own hydrological research programs. Of particular importance were Leroy Sherman's unit hydrograph , the infiltration theory of Robert E. Horton , and C.V. Theis' aquifer test/equation describing well hydraulics. Since the 1950s, hydrology has been approached with a more theoretical basis than in the past, facilitated by advances in the physical understanding of hydrological processes and by

1081-727: The Ancient Age. In more modern times, these works include the Alexander von Humboldt ( Kosmos ) in the nineteenth century, in which geography is regarded as a physical and natural science through the work Summa de Geografía of Martín Fernández de Enciso from the early sixteenth century, which indicated for the first time the New World. During the eighteenth and nineteenth centuries, a controversy exported from geology, between supporters of James Hutton (uniformitarianism thesis) and Georges Cuvier (catastrophism) strongly influenced

1128-564: The advent of computers and especially geographic information systems (GIS). (See also GIS and hydrology ) The central theme of hydrology is that water circulates throughout the Earth through different pathways and at different rates. The most vivid image of this is in the evaporation of water from the ocean, which forms clouds. These clouds drift over the land and produce rain. The rainwater flows into lakes, rivers, or aquifers. The water in lakes, rivers, and aquifers then either evaporates back to

1175-530: The atmosphere or eventually flows back to the ocean, completing a cycle. Water changes its state of being several times throughout this cycle. The areas of research within hydrology concern the movement of water between its various states, or within a given state, or simply quantifying the amounts in these states in a given region. Parts of hydrology concern developing methods for directly measuring these flows or amounts of water, while others concern modeling these processes either for scientific knowledge or for making

1222-553: The birth of geography as a science during the Greek classical period and until the late nineteenth century with the birth of anthropogeography (human geography), geography was almost exclusively a natural science: the study of location and descriptive gazetteer of all places of the known world. Several works among the best known during this long period could be cited as an example, from Strabo ( Geography ), Eratosthenes ( Geographika ) or Dionysius Periegetes ( Periegesis Oiceumene ) in

1269-527: The council and its committees, supervising implementation and reporting on the council's resolutions, and discharging all other duties which it is assigned by the council. IHP's activities are implemented by the efforts of its secretariat, located in UNESCO headquarters in Paris. The secretariat provides studies, information, and the facilities needed to employ the program's activities. The backbone of IHP, however,

1316-401: The evolution of the landscape. For hydrology, glaciology, and climatology as a boost investigated as studying geographic factors shape the landscape and affect the cycle. The bulk of the work of William Morris Davis led to the development of a new branch of physical geography: Geomorphology whose contents until then did not differ from the rest of geography. Shortly after this branch would present

1363-617: The field of geography, because geography at this time was a natural science. Two historical events during the nineteenth century had a great effect on the further development of physical geography. The first was the European colonial expansion in Asia , Africa , Australia and even America in search of raw materials required by industries during the Industrial Revolution . This fostered the creation of geography departments in

1410-491: The field to develop cycle of erosion theory which he proposed as a paradigm for geography in general, although in actually served as a paradigm for physical geography. His theory explained that mountains and other landforms are shaped by factors that are manifested cyclically. He explained that the cycle begins with the lifting of the relief by geological processes (faults, volcanism, tectonic upheaval, etc.). Factors such as rivers and runoff begin to create V-shaped valleys between

1457-692: The future behavior of hydrologic systems (water flow, water quality). One of the major current concerns in hydrologic research is "Prediction in Ungauged Basins" (PUB), i.e. in basins where no or only very few data exist. The aims of Statistical hydrology is to provide appropriate statistical methods for analyzing and modeling various parts of the hydrological cycle. By analyzing the statistical properties of hydrologic records, such as rainfall or river flow, hydrologists can estimate future hydrologic phenomena. When making assessments of how often relatively rare events will occur, analyses are made in terms of

International Hydrological Programme - Misplaced Pages Continue

1504-465: The hydrologic cycle, in which precipitation falling in the mountains infiltrated the Earth's surface and led to streams and springs in the lowlands. With the adoption of a more scientific approach, Leonardo da Vinci and Bernard Palissy independently reached an accurate representation of the hydrologic cycle. It was not until the 17th century that hydrologic variables began to be quantified. Pioneers of

1551-430: The important areas of hydrology is the interchange between rivers and aquifers. Groundwater/surface water interactions in streams and aquifers can be complex and the direction of net water flux (into surface water or into the aquifer) may vary spatially along a stream channel and over time at any particular location, depending on the relationship between stream stage and groundwater levels. In some considerations, hydrology

1598-403: The maximum rate at which the soil can absorb water, depends on several factors. The layer that is already saturated provides a resistance that is proportional to its thickness, while that plus the depth of water above the soil provides the driving force ( hydraulic head ). Dry soil can allow rapid infiltration by capillary action ; this force diminishes as the soil becomes wet. Compaction reduces

1645-521: The members are newcomers and the rest are halfway through their term. The council normally meets once every two years, although extraordinary sessions may be convened under the conditions specified in the Rules of Procedure. At the beginning of its first session, the council elects a chairperson and four vice-chairpersons. These constitute the IHP Bureau, which is responsible for coordinating sessions of

1692-523: The modern science of hydrology include Pierre Perrault , Edme Mariotte and Edmund Halley . By measuring rainfall, runoff, and drainage area, Perrault showed that rainfall was sufficient to account for the flow of the Seine. Mariotte combined velocity and river cross-section measurements to obtain a discharge value, again in the Seine. Halley showed that the evaporation from the Mediterranean Sea

1739-451: The mountains (the stage called "youth"). During this first stage, the terrain is steeper and more irregular. Over time, the currents can carve wider valleys ("maturity") and then start to wind, towering hills only ("senescence"). Finally, everything comes to what is a plain flat plain at the lowest elevation possible (called "baseline") This plain was called by Davis' " peneplain " meaning "almost plain" Then river rejuvenation occurs and there

1786-406: The paleogeography through his work "The climates of the geological past" which is considered the father of paleoclimatology . Russian geographers who made great contributions to the discipline in this period were: NM Sibirtsev , Pyotr Semyonov , K.D. Glinka , Neustrayev , among others. The second important process is the theory of evolution by Darwin in mid-century (which decisively influenced

1833-530: The patriarch of Russian geography, Mikhail Lomonosov . In the mid-1750s Lomonosov began working in the Department of Geography, Academy of Sciences to conduct research in Siberia. They showed the organic origin of soil and developed a comprehensive law on the movement of the ice, thereby founding a new branch of geography: glaciology . In 1755 on his initiative was founded Moscow University where he promoted

1880-461: The porosity and the pore sizes. Surface cover increases capacity by retarding runoff, reducing compaction and other processes. Higher temperatures reduce viscosity , increasing infiltration. Soil moisture can be measured in various ways; by capacitance probe , time domain reflectometer or tensiometer . Other methods include solute sampling and geophysical methods. Hydrology considers quantifying surface water flow and solute transport, although

1927-611: The results of research carried out in universities and various other research institutions. Most journals cover a specific publish the research within that field, however unlike human geographers, physical geographers tend to publish in inter-disciplinary journals rather than predominantly geography journal; the research is normally expressed in the form of a scientific paper . Additionally, textbooks, books, and communicate research to laypeople, although these tend to focus on environmental issues or cultural dilemmas. Examples of journals that publish articles from physical geographers are: From

International Hydrological Programme - Misplaced Pages Continue

1974-567: The study of geography and the training of geographers. In 1758 he was appointed director of the Department of Geography, Academy of Sciences, a post from which would develop a working methodology for geographical survey guided by the most important long expeditions and geographical studies in Russia. The contributions of the Russian school became more frequent through his disciples, and in the nineteenth century we have great geographers such as Vasily Dokuchaev who performed works of great importance as

2021-440: The treatment of flows in large rivers is sometimes considered as a distinct topic of hydraulics or hydrodynamics. Surface water flow can include flow both in recognizable river channels and otherwise. Methods for measuring flow once the water has reached a river include the stream gauge (see: discharge ), and tracer techniques. Other topics include chemical transport as part of surface water, sediment transport and erosion. One of

2068-409: The universities of the colonial powers and the birth and development of national geographical societies, thus giving rise to the process identified by Horacio Capel as the institutionalization of geography. The exploration of Siberia is an example. In the mid-eighteenth century, many geographers were sent to perform geographical surveys in the area of Arctic Siberia . Among these is who is considered

2115-604: The variables constituting the terrestrial water balance, for example surface water storage, soil moisture , precipitation , evapotranspiration , and snow and ice , are measurable using remote sensing at various spatial-temporal resolutions and accuracies. Sources of remote sensing include land-based sensors, airborne sensors and satellite sensors which can capture microwave , thermal and near-infrared data or use lidar , for example. In hydrology, studies of water quality concern organic and inorganic compounds, and both dissolved and sediment material. In addition, water quality

2162-481: The work of Friedrich Ratzel , who had academic training as a zoologist and was a follower of Darwin's ideas) which meant an important impetus in the development of Biogeography. Another major event in the late nineteenth and early twentieth centuries took place in the United States . William Morris Davis not only made important contributions to the establishment of discipline in his country but revolutionized

2209-618: Was sufficient to account for the outflow of rivers flowing into the sea. Advances in the 18th century included the Bernoulli piezometer and Bernoulli's equation , by Daniel Bernoulli , and the Pitot tube , by Henri Pitot . The 19th century saw development in groundwater hydrology, including Darcy's law , the Dupuit-Thiem well formula, and Hagen- Poiseuille 's capillary flow equation. Rational analyses began to replace empiricism in

#975024