The Ecker Dam ( German : Eckertalsperre ) is a gravity dam in the Harz mountain range near Bad Harzburg , Germany . Constructed between 1939 and 1943, it is today operated by the Harzwasserwerke company. The dam's reservoir impounds the waters of the Ecker river and mainly serves for drinking water supply .
98-424: The dam is used for the supply of drinking water , flood protection , and raising water levels during times of low rainfall. With an average discharge of 16 million m³ per year, it provides drinking water to the cities of Brunswick , Wolfenbüttel , and Wolfsburg . A pipe system leads to a central water tower near Liebenburg , where the waters of the nearby Grane Dam are also collected. Electricity generation
196-424: A cirque landform (alternatively known as a corrie or as a cwm ) – a typically armchair-shaped geological feature (such as a depression between mountains enclosed by arêtes ) – which collects and compresses through gravity the snow that falls into it. This snow accumulates and the weight of the snow falling above compacts it, forming névé (granular snow). Further crushing of the individual snowflakes and squeezing
294-456: A breakdown or design fault in the sanitation system, or by chemical contaminants. Further examples of contamination include: Examples of chemical contamination include: Most water requires some treatment before use; even water from deep wells or springs. The extent of treatment depends on the source of the water. Appropriate technology options in water treatment include both community-scale and household-scale point-of-use (POU) designs. Only
392-452: A chronic health risk through buildup of heavy metals although some components like nitrates/nitrites and arsenic can have a more immediate impact. Physical parameters affect the aesthetics and taste of the drinking water and may complicate the removal of microbial pathogens. Pesticides are also potential drinking water contaminants of the category chemical contaminants . Pesticides may be present in drinking water in low concentrations, but
490-566: A component of effective policy for health protection." In 1990, only 76 percent of the global population had access to drinking water. By 2015 that number had increased to 91 percent. In 1990, most countries in Latin America, East and South Asia, and Sub-Saharan Africa were well below 90%. In Sub-Saharan Africa, where the rates are lowest, household access ranges from 40 to 80 percent. Countries that experience violent conflict can have reductions in drinking water access: One study found that
588-523: A conflict with about 2,500 battle deaths deprives 1.8% of the population of potable water. Typically in developed countries , tap water meets drinking water quality standards , even though only a small proportion is actually consumed or used in food preparation. Other typical uses for tap water include washing, toilets, and irrigation . Greywater may also be used for toilets or irrigation. Its use for irrigation however may be associated with risks. Globally, by 2015, 89% of people had access to water from
686-586: A farmer might plan for 35 U.S. gallons (130 L) per day for a dairy cow , a third of that for a horse , and a tenth of that for a hog . However, relatively few studies have been focused on the drinking behavior of wild animals. According to the World Health Organization's 2017 report, safe drinking water is water that "does not represent any significant risk to health over a lifetime of consumption, including different sensitivities that may occur between life stages". According to
784-421: A few large urban areas such as Christchurch , New Zealand have access to sufficiently pure water of sufficient volume that no treatment of the raw water is required. In emergency situations when conventional treatment systems have been compromised, waterborne pathogens may be killed or inactivated by boiling but this requires abundant sources of fuel, and can be very onerous on consumers, especially where it
882-522: A glacier is usually assessed by determining the glacier mass balance or observing terminus behavior. Healthy glaciers have large accumulation zones, more than 60% of their area is snow-covered at the end of the melt season, and they have a terminus with a vigorous flow. Following the Little Ice Age 's end around 1850, glaciers around the Earth have retreated substantially . A slight cooling led to
980-601: A glacier may flow into a body of water, it forms only on land and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water. On Earth, 99% of glacial ice is contained within vast ice sheets (also known as "continental glaciers") in the polar regions , but glaciers may be found in mountain ranges on every continent other than the Australian mainland, including Oceania's high-latitude oceanic island countries such as New Zealand . Between latitudes 35°N and 35°S, glaciers occur only in
1078-411: A glacier via moulins . Streams within or beneath a glacier flow in englacial or sub-glacial tunnels. These tunnels sometimes reemerge at the glacier's surface. Most of the important processes controlling glacial motion occur in the ice-bed contact—even though it is only a few meters thick. The bed's temperature, roughness and softness define basal shear stress, which in turn defines whether movement of
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#17327733197731176-630: A hardship. The WHO/ UNICEF Joint Monitoring Program (JMP) for Water Supply and Sanitation is the official United Nations mechanism tasked with monitoring progress towards the Millennium Development Goal (MDG) relating to drinking-water and sanitation (MDG 7, Target 7c), which is to: "Halve, by 2015, the proportion of people without sustainable access to safe drinking-water and basic sanitation". Glacier A glacier ( US : / ˈ ɡ l eɪ ʃ ər / ; UK : / ˈ ɡ l æ s i ər , ˈ ɡ l eɪ s i ər / )
1274-407: A hot climate, up to 16 litres (4.2 US gal) a day may be required. About 1 to 2 billion people lack safe drinking water. Water can carry vectors of disease . More people die from unsafe water than from war, then- U.N. secretary-general Ban Ki-moon said in 2010. Developing countries are most affected by unsafe drinking water. Potable water is available in almost all populated areas of
1372-408: A kilometer per year. Eventually, the ice will be surging fast enough that it begins to thin, as accumulation cannot keep up with the transport. This thinning will increase the conductive heat loss, slowing the glacier and causing freezing. This freezing will slow the glacier further, often until it is stationary, whence the cycle can begin again. The flow of water under the glacial surface can have
1470-404: A large effect on the motion of the glacier itself. Subglacial lakes contain significant amounts of water, which can move fast: cubic kilometers can be transported between lakes over the course of a couple of years. This motion is thought to occur in two main modes: pipe flow involves liquid water moving through pipe-like conduits, like a sub-glacial river; sheet flow involves motion of water in
1568-460: A lower heat conductance, meaning that the basal temperature is also likely to be higher. Bed temperature tends to vary in a cyclic fashion. A cool bed has a high strength, reducing the speed of the glacier. This increases the rate of accumulation, since newly fallen snow is not transported away. Consequently, the glacier thickens, with three consequences: firstly, the bed is better insulated, allowing greater retention of geothermal heat. Secondly,
1666-777: A negative effect on child development (both physical and cognitive). Sixty million people are estimated to have been poisoned by well water contaminated by excessive fluoride , which dissolved from granite rocks. The effects are particularly evident in the bone deformations of children. Similar or larger problems are anticipated in other countries including China, Uzbekistan, and Ethiopia. Although helpful for dental health in low dosage, fluoride in large amounts interferes with bone formation. Long-term consumption of water with high fluoride concentration (> 1.5 ppm F) can have serious undesirable consequences such as dental fluorosis , enamel mottle and skeletal fluorosis , bone deformities in children. Fluorosis severity depends on how much fluoride
1764-451: A report by UNICEF and UNESCO , Finland has the best drinking water quality in the world. Parameters for drinking water quality typically fall within three categories: microbiological, chemical, physical. Microbiological parameters include coliform bacteria , E. coli , and specific pathogenic species of bacteria (such as cholera -causing Vibrio cholerae ), viruses , and protozoan parasites . Originally, fecal contamination
1862-578: A source that is suitable for drinking – called improved water source – and 71% of the world could access safely managed drinking water that is clean and available on-demand. Estimates suggest that at least 25% of improved sources contain fecal contamination. 1.8 billion people still use an unsafe drinking water source which may be contaminated by feces . This can result in infectious diseases , such as gastroenteritis , cholera , and typhoid , among others. Reduction of waterborne diseases and development of safe water resources
1960-481: A source that is suitable for drinking – called improved water sources . In sub-Saharan Africa , access to potable water ranged from 40% to 80% of the population. Nearly 4.2 billion people worldwide had access to tap water, while another 2.4 billion had access to wells or public taps. By 2015, 5.2 billion people representing 71% of the global population used safely managed drinking water services. As of 2017, 90% of people having access to water from
2058-488: A thin layer. A switch between the two flow conditions may be associated with surging behavior. Indeed, the loss of sub-glacial water supply has been linked with the shut-down of ice movement in the Kamb ice stream. The subglacial motion of water is expressed in the surface topography of ice sheets, which slump down into vacated subglacial lakes. The speed of glacial displacement is partly determined by friction . Friction makes
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#17327733197732156-410: A tremendous impact as the iceberg strikes the water. Tidewater glaciers undergo centuries-long cycles of advance and retreat that are much less affected by climate change than other glaciers. Thermally, a temperate glacier is at a melting point throughout the year, from its surface to its base. The ice of a polar glacier is always below the freezing threshold from the surface to its base, although
2254-493: A year. Leakage of untreated and treated water from pipes reduces access to water. Leakage rates of 50% are not uncommon in urban systems. Tap water , delivered by domestic water systems refers to water piped to homes and delivered to a tap or spigot. In the United States, the typical water consumption per capita, at home, is 69.3 US gallons (262 L; 57.7 imp gal) of water per day. Of this, only 1% of
2352-574: A year. The reservoir uses a section of the river valley which, below a prominent trough end , was dug out in the shape of a basin by an ice age glacier. Construction started in 1939, mainly to meet the increasing demand for drinking water in the Brunswick greater area and around the recently opened Wolfsburg Volkswagen Plant . For the first time in Germany, coarse-grained concrete ( Rüttelgrobbeton ) with an aggregate of up to 300 mm grain size
2450-517: Is WASH - standing for water, sanitation and hygiene . The WHO has investigated which proportion of death and disease worldwide can be attributed to insufficient WASH services. In their analysis they focus on the following four health outcomes: diarrhea , acute respiratory infections , malnutrition , and soil-transmitted Helminthiasis (STHs). These health outcomes are also included as an indicator for achieving Sustainable Development Goal 3 ("Good Health and Well-being"): Indicator 3.9.2 reports on
2548-419: Is atmospheric water generators . Springs are often used as sources for bottled waters . The most efficient and convenient way to transport and deliver potable water is through pipes. Plumbing can require significant capital investment. Some systems suffer high operating costs. The cost to replace the deteriorating water and sanitation infrastructure of industrialized countries may be as high as $ 200 billion
2646-427: Is water that is safe for ingestion , either when drunk directly in liquid form or consumed indirectly through food preparation . It is often (but not always) supplied through taps, in which case it is also called tap water . The amount of drinking water required to maintain good health varies, and depends on physical activity level, age, health-related issues, and environmental conditions. For those who work in
2744-436: Is a major public health goal in developing countries. In 2017, almost 22 million Americans drank from water systems that were in violation of public health standards, which could contribute to citizens developing water-borne illnesses . Safe drinking water is an environmental health concern. Bottled water is sold for public consumption in most parts of the world. Improved sources are also monitored based on whether water
2842-468: Is a persistent body of dense ice that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries . It acquires distinguishing features, such as crevasses and seracs , as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques , moraines , or fjords . Although
2940-456: Is above or at freezing at the interface and is able to slide at this contact. This contrast is thought to a large extent to govern the ability of a glacier to effectively erode its bed , as sliding ice promotes plucking at rock from the surface below. Glaciers which are partly cold-based and partly warm-based are known as polythermal . Glaciers form where the accumulation of snow and ice exceeds ablation . A glacier usually originates from
3038-407: Is affected by factors such as slope, ice thickness, snowfall, longitudinal confinement, basal temperature, meltwater production, and bed hardness. A few glaciers have periods of very rapid advancement called surges . These glaciers exhibit normal movement until suddenly they accelerate, then return to their previous movement state. These surges may be caused by the failure of the underlying bedrock,
Ecker Dam - Misplaced Pages Continue
3136-779: Is also provided through a small hydropower plant, operated by two turbines with an installed capacity of 2 x 300 kW and an annual generation of 1,400,000 kWh. The Ecker Dam was the third modern reservoir built in the Harz mountains, after the construction of the Söse Dam in 1928–1931 and the Oder Dam in 1930–1933. It was laid out in the Ecker catchment area at the foot of the Brocken massif, characterised by extended upland bogs and heavy precipitation of up to 1,700 mm (67 in)
3234-658: Is available when needed (5.8 billion people), located on premises (5.4 billion), free from contamination (5.4 billion), and within a 30-minute round trip. While improved water sources such as protected piped water are more likely to provide safe and adequate water as they may prevent contact with human excreta, for example, this is not always the case. According to a 2014 study, approximately 25% of improved sources contained fecal contamination. The population in Australia, New Zealand, North America and Europe have achieved nearly universal basic drinking water services. Because of
3332-411: Is because these peaks are located near or in the hyperarid Atacama Desert . Glaciers erode terrain through two principal processes: plucking and abrasion . As glaciers flow over bedrock, they soften and lift blocks of rock into the ice. This process, called plucking, is caused by subglacial water that penetrates fractures in the bedrock and subsequently freezes and expands. This expansion causes
3430-406: Is by basal sliding, where meltwater forms between the ice and the bed itself. Whether a bed is hard or soft depends on the porosity and pore pressure; higher porosity decreases the sediment strength (thus increases the shear stress τ B ). Porosity may vary through a range of methods. Bed softness may vary in space or time, and changes dramatically from glacier to glacier. An important factor
3528-647: Is called desalination and is used mainly in dry areas with access to large bodies of saltwater. Publicly available treated water has historically been associated with major increases in life expectancy and improved public health . Water disinfection can greatly reduce the risks of waterborne diseases such as typhoid and cholera . Chlorination is currently the most widely used water disinfection method, although chlorine compounds can react with substances in water and produce disinfection by-products (DBP) that pose problems to human health. Local geological conditions affecting groundwater are determining factors for
3626-434: Is called glaciology . Glaciers are important components of the global cryosphere . Glaciers are categorized by their morphology, thermal characteristics, and behavior. Alpine glaciers form on the crests and slopes of mountains. A glacier that fills a valley is called a valley glacier , or alternatively, an alpine glacier or mountain glacier . A large body of glacial ice astride a mountain, mountain range, or volcano
3724-416: Is called rock flour and is made up of rock grains between 0.002 and 0.00625 mm in size. Abrasion leads to steeper valley walls and mountain slopes in alpine settings, which can cause avalanches and rock slides, which add even more material to the glacier. Glacial abrasion is commonly characterized by glacial striations . Glaciers produce these when they contain large boulders that carve long scratches in
3822-427: Is difficult to store boiled water in sterile conditions. Other techniques, such as filtration, chemical disinfection, and exposure to ultraviolet radiation (including solar UV) have been demonstrated in an array of randomized control trials to significantly reduce levels of water-borne disease among users in low-income countries, but these suffer from the same problems as boiling methods. Another type of water treatment
3920-647: Is higher, and the mountains above 5,000 m (16,400 ft) usually have permanent snow. Even at high latitudes, glacier formation is not inevitable. Areas of the Arctic , such as Banks Island , and the McMurdo Dry Valleys in Antarctica are considered polar deserts where glaciers cannot form because they receive little snowfall despite the bitter cold. Cold air, unlike warm air, is unable to transport much water vapor. Even during glacial periods of
4018-513: Is present in the water, as well as people's diet and physical activity. Defluoridation methods include membrane-based methods, precipitation, absorption, and electrocoagulation. Natural arsenic contamination of groundwater is a global threat with 140 million people affected in 70 countries globally. Some well-known examples of water quality problems with drinking water supplies include: Water supply can get contaminated by pathogens which may originate from human excreta , for example due to
Ecker Dam - Misplaced Pages Continue
4116-897: Is termed an ice cap or ice field . Ice caps have an area less than 50,000 km (19,000 sq mi) by definition. Glacial bodies larger than 50,000 km (19,000 sq mi) are called ice sheets or continental glaciers . Several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces. The only extant ice sheets are the two that cover most of Antarctica and Greenland. They contain vast quantities of freshwater, enough that if both melted, global sea levels would rise by over 70 m (230 ft). Portions of an ice sheet or cap that extend into water are called ice shelves ; they tend to be thin with limited slopes and reduced velocities. Narrow, fast-moving sections of an ice sheet are called ice streams . In Antarctica, many ice streams drain into large ice shelves . Some drain directly into
4214-413: Is the region where there is a net loss in glacier mass. The upper part of a glacier, where accumulation exceeds ablation, is called the accumulation zone . The equilibrium line separates the ablation zone and the accumulation zone; it is the contour where the amount of new snow gained by accumulation is equal to the amount of ice lost through ablation. In general, the accumulation zone accounts for 60–70% of
4312-402: Is the underlying geology; glacial speeds tend to differ more when they change bedrock than when the gradient changes. Further, bed roughness can also act to slow glacial motion. The roughness of the bed is a measure of how many boulders and obstacles protrude into the overlying ice. Ice flows around these obstacles by melting under the high pressure on their stoss side ; the resultant meltwater
4410-552: Is then forced into the cavity arising in their lee side , where it re-freezes. As well as affecting the sediment stress, fluid pressure (p w ) can affect the friction between the glacier and the bed. High fluid pressure provides a buoyancy force upwards on the glacier, reducing the friction at its base. The fluid pressure is compared to the ice overburden pressure, p i , given by ρgh. Under fast-flowing ice streams, these two pressures will be approximately equal, with an effective pressure (p i – p w ) of 30 kPa; i.e. all of
4508-458: Is to reach large numbers of low-income households on a sustainable basis. Few POU measures have reached significant scale thus far, but efforts to promote and commercially distribute these products to the world's poor have only been under way for a few years. Solar water disinfection is a low-cost method of purifying water that can often be implemented with locally available materials. Unlike methods that rely on firewood , it has low impact on
4606-993: The Andes , the Himalayas , the Rocky Mountains , the Caucasus , Scandinavian Mountains , and the Alps . Snezhnika glacier in Pirin Mountain, Bulgaria with a latitude of 41°46′09″ N is the southernmost glacial mass in Europe. Mainland Australia currently contains no glaciers, although a small glacier on Mount Kosciuszko was present in the last glacial period . In New Guinea, small, rapidly diminishing, glaciers are located on Puncak Jaya . Africa has glaciers on Mount Kilimanjaro in Tanzania, on Mount Kenya , and in
4704-671: The European Drinking Water Directive and in the United States, the United States Environmental Protection Agency (EPA) establishes standards as required by the Safe Drinking Water Act . China adopted its own drinking water standard GB3838-2002 (Type II) enacted by Ministry of Environmental Protection in 2002. For countries without a legislative or administrative framework for such standards,
4802-644: The Faroe and Crozet Islands were completely glaciated. The permanent snow cover necessary for glacier formation is affected by factors such as the degree of slope on the land, amount of snowfall and the winds. Glaciers can be found in all latitudes except from 20° to 27° north and south of the equator where the presence of the descending limb of the Hadley circulation lowers precipitation so much that with high insolation snow lines reach above 6,500 m (21,330 ft). Between 19˚N and 19˚S, however, precipitation
4900-760: The Himalayas , Andes , and a few high mountains in East Africa, Mexico, New Guinea and on Zard-Kuh in Iran. With more than 7,000 known glaciers, Pakistan has more glacial ice than any other country outside the polar regions. Glaciers cover about 10% of Earth's land surface. Continental glaciers cover nearly 13 million km (5 million sq mi) or about 98% of Antarctica 's 13.2 million km (5.1 million sq mi), with an average thickness of ice 2,100 m (7,000 ft). Greenland and Patagonia also have huge expanses of continental glaciers. The volume of glaciers, not including
4998-562: The Quaternary , Manchuria , lowland Siberia , and central and northern Alaska , though extraordinarily cold, had such light snowfall that glaciers could not form. In addition to the dry, unglaciated polar regions, some mountains and volcanoes in Bolivia, Chile and Argentina are high (4,500 to 6,900 m or 14,800 to 22,600 ft) and cold, but the relative lack of precipitation prevents snow from accumulating into glaciers. This
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#17327733197735096-535: The Rwenzori Mountains . Oceanic islands with glaciers include Iceland, several of the islands off the coast of Norway including Svalbard and Jan Mayen to the far north, New Zealand and the subantarctic islands of Marion , Heard , Grande Terre (Kerguelen) and Bouvet . During glacial periods of the Quaternary, Taiwan , Hawaii on Mauna Kea and Tenerife also had large alpine glaciers, while
5194-528: The World Health Organization publishes guidelines on the standards that should be achieved. The World Health Organization considers access to safe drinking-water a basic human right. Contaminated water is estimated to result in more than half a million deaths per year. Contaminated water together with the lack of sanitation was estimated to cause about one percent of disability adjusted life years worldwide in 2010. According to
5292-692: The toxicity of the chemical and the extent of human exposure are factors that are used to determine the specific health risk. Perfluorinated alkylated substances (PFAS) are a group of synthetic compounds used in a large variety of consumer products, such as food packaging , waterproof fabrics, carpeting and cookware. PFAS are known to persist in the environment and are commonly described as persistent organic pollutants . PFAS chemicals have been detected in blood, both humans and animals, worldwide, as well as in food products, water, air and soil. Animal testing studies with PFAS have shown effects on growth and development, and possibly effects on reproduction, thyroid,
5390-567: The "mortality rate attributed to unsafe water, sanitation, and lack of hygiene". Diarrhea is primarily transmitted through fecal–oral routes . In 2011, infectious diarrhea resulted in about 0.7 million deaths in children under five years old and 250 million lost school days. This equates to about 2000 child deaths per day. Children suffering from diarrhea are more vulnerable to become underweight (due to stunted growth ). This makes them more vulnerable to other diseases such as acute respiratory infections and malaria . Chronic diarrhea can have
5488-448: The 1990s and 2000s. In a study using data from January 1993 through October 2005, more events were detected every year since 2002, and twice as many events were recorded in 2005 as there were in any other year. Ogives or Forbes bands are alternating wave crests and valleys that appear as dark and light bands of ice on glacier surfaces. They are linked to seasonal motion of glaciers; the width of one dark and one light band generally equals
5586-510: The WHO, the most common diseases linked with poor water quality are cholera , diarrhea , dysentery , hepatitis A , typhoid , and polio . One of the main causes for contaminated drinking water in developing countries is lack of sanitation and poor hygiene. For this reason, the quantification of the burden of disease from consuming contaminated drinking water usually looks at water, sanitation and hygiene aspects together. The acronym for this
5684-412: The advance of many alpine glaciers between 1950 and 1985, but since 1985 glacier retreat and mass loss has become larger and increasingly ubiquitous. Glaciers move downhill by the force of gravity and the internal deformation of ice. At the molecular level, ice consists of stacked layers of molecules with relatively weak bonds between layers. When the amount of strain (deformation) is proportional to
5782-520: The air from the snow turns it into "glacial ice". This glacial ice will fill the cirque until it "overflows" through a geological weakness or vacancy, such as a gap between two mountains. When the mass of snow and ice reaches sufficient thickness, it begins to move by a combination of surface slope, gravity, and pressure. On steeper slopes, this can occur with as little as 15 m (49 ft) of snow-ice. In temperate glaciers, snow repeatedly freezes and thaws, changing into granular ice called firn . Under
5880-430: The amount of melting at surface of the glacier, the faster the ice will flow. Basal sliding is dominant in temperate or warm-based glaciers. The presence of basal meltwater depends on both bed temperature and other factors. For instance, the melting point of water decreases under pressure, meaning that water melts at a lower temperature under thicker glaciers. This acts as a "double whammy", because thicker glaciers have
5978-713: The annual movement of the glacier. Ogives are formed when ice from an icefall is severely broken up, increasing ablation surface area during summer. This creates a swale and space for snow accumulation in the winter, which in turn creates a ridge. Sometimes ogives consist only of undulations or color bands and are described as wave ogives or band ogives. Glaciers are present on every continent and in approximately fifty countries, excluding those (Australia, South Africa) that have glaciers only on distant subantarctic island territories. Extensive glaciers are found in Antarctica, Argentina, Chile, Canada, Pakistan, Alaska, Greenland and Iceland. Mountain glaciers are widespread, especially in
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#17327733197736076-432: The bedrock has frequent fractures on the surface, glacial erosion rates tend to increase as plucking is the main erosive force on the surface; when the bedrock has wide gaps between sporadic fractures, however, abrasion tends to be the dominant erosive form and glacial erosion rates become slow. Glaciers in lower latitudes tend to be much more erosive than glaciers in higher latitudes, because they have more meltwater reaching
6174-445: The bedrock. By mapping the direction of the striations, researchers can determine the direction of the glacier's movement. Similar to striations are chatter marks , lines of crescent-shape depressions in the rock underlying a glacier. They are formed by abrasion when boulders in the glacier are repeatedly caught and released as they are dragged along the bedrock. The rate of glacier erosion varies. Six factors control erosion rate: When
6272-571: The created ice's density. The word glacier is a loanword from French and goes back, via Franco-Provençal , to the Vulgar Latin glaciārium , derived from the Late Latin glacia , and ultimately Latin glaciēs , meaning "ice". The processes and features caused by or related to glaciers are referred to as glacial. The process of glacier establishment, growth and flow is called glaciation . The corresponding area of study
6370-586: The dam crest and only about two-thirds of the facilities were accessible from the west. Access rights to operate the facilities were settled by bilateral agreements in the late 1970s. Though not accessible by car, the Ecker Dam and the circular trail around its reservoir are popular destinations for daytrippers. The dam wall is checkpoint no. 1 in the Harzer Wandernadel hiking trail network. Drinking water Drinking water or potable water
6468-467: The deep profile of fjords , which can reach a kilometer in depth as ice is topographically steered into them. The extension of fjords inland increases the rate of ice sheet thinning since they are the principal conduits for draining ice sheets. It also makes the ice sheets more sensitive to changes in climate and the ocean. Although evidence in favor of glacial flow was known by the early 19th century, other theories of glacial motion were advanced, such as
6566-483: The deformation to become a plastic flow rather than elastic. Then, the glacier will begin to deform under its own weight and flow across the landscape. According to the Glen–Nye flow law , the relationship between stress and strain, and thus the rate of internal flow, can be modeled as follows: where: The lowest velocities are near the base of the glacier and along valley sides where friction acts against flow, causing
6664-404: The environment. In many areas, low concentration of fluoride (< 1.0 ppm F) is intentionally added to tap water to improve dental health , although in some communities water fluoridation remains a controversial issue. (See water fluoridation controversy ). According to the World Health Organization (WHO), "access to safe drinking-water is essential to health, a basic human right and
6762-418: The essentially correct explanation in the 1840s, although it was several decades before it was fully accepted. The top 50 m (160 ft) of a glacier are rigid because they are under low pressure . This upper section is known as the fracture zone and moves mostly as a single unit over the plastic-flowing lower section. When a glacier moves through irregular terrain, cracks called crevasses develop in
6860-475: The fracture zone. Crevasses form because of differences in glacier velocity. If two rigid sections of a glacier move at different speeds or directions, shear forces cause them to break apart, opening a crevasse. Crevasses are seldom more than 46 m (150 ft) deep but, in some cases, can be at least 300 m (1,000 ft) deep. Beneath this point, the plasticity of the ice prevents the formation of cracks. Intersecting crevasses can create isolated peaks in
6958-453: The glacier to melt, creating a water source that is especially important for plants, animals and human uses when other sources may be scant. However, within high-altitude and Antarctic environments, the seasonal temperature difference is often not sufficient to release meltwater. Since glacial mass is affected by long-term climatic changes, e.g., precipitation , mean temperature , and cloud cover , glacial mass changes are considered among
7056-428: The glacier will be accommodated by motion in the sediments, or if it'll be able to slide. A soft bed, with high porosity and low pore fluid pressure, allows the glacier to move by sediment sliding: the base of the glacier may even remain frozen to the bed, where the underlying sediment slips underneath it like a tube of toothpaste. A hard bed cannot deform in this way; therefore the only way for hard-based glaciers to move
7154-510: The glacier's surface area, more if the glacier calves icebergs. Ice in the accumulation zone is deep enough to exert a downward force that erodes underlying rock. After a glacier melts, it often leaves behind a bowl- or amphitheater-shaped depression that ranges in size from large basins like the Great Lakes to smaller mountain depressions known as cirques . The accumulation zone can be subdivided based on its melt conditions. The health of
7252-535: The high initial investments, many less wealthy nations cannot afford to develop or sustain appropriate infrastructure, and as a consequence people in these areas may spend a correspondingly higher fraction of their income on water. 2003 statistics from El Salvador, for example, indicate that the poorest 20% of households spend more than 10% of their total income on water. In the United Kingdom, authorities define spending of more than 3% of one's income on water as
7350-619: The ice at the bottom of the glacier move more slowly than ice at the top. In alpine glaciers, friction is also generated at the valley's sidewalls, which slows the edges relative to the center. Mean glacial speed varies greatly but is typically around 1 m (3 ft) per day. There may be no motion in stagnant areas; for example, in parts of Alaska, trees can establish themselves on surface sediment deposits. In other cases, glaciers can move as fast as 20–30 m (70–100 ft) per day, such as in Greenland's Jakobshavn Isbræ . Glacial speed
7448-420: The ice sheets of Antarctica and Greenland, has been estimated at 170,000 km . Glacial ice is the largest reservoir of fresh water on Earth, holding with ice sheets about 69 percent of the world's freshwater. Many glaciers from temperate , alpine and seasonal polar climates store water as ice during the colder seasons and release it later in the form of meltwater as warmer summer temperatures cause
7546-556: The ice to act as a lever that loosens the rock by lifting it. Thus, sediments of all sizes become part of the glacier's load. If a retreating glacier gains enough debris, it may become a rock glacier , like the Timpanogos Glacier in Utah. Abrasion occurs when the ice and its load of rock fragments slide over bedrock and function as sandpaper, smoothing and polishing the bedrock below. The pulverized rock this process produces
7644-488: The ice, called seracs . Crevasses can form in several different ways. Transverse crevasses are transverse to flow and form where steeper slopes cause a glacier to accelerate. Longitudinal crevasses form semi-parallel to flow where a glacier expands laterally. Marginal crevasses form near the edge of the glacier, caused by the reduction in speed caused by friction of the valley walls. Marginal crevasses are largely transverse to flow. Moving glacier ice can sometimes separate from
7742-411: The idea that meltwater, refreezing inside glaciers, caused the glacier to dilate and extend its length. As it became clear that glaciers behaved to some degree as if the ice were a viscous fluid, it was argued that "regelation", or the melting and refreezing of ice at a temperature lowered by the pressure on the ice inside the glacier, was what allowed the ice to deform and flow. James Forbes came up with
7840-402: The immune system and liver. As of 2022 the health impacts of many PFAS compounds are not understood. Scientists are conducting research to determine the extent and severity of impacts from PFAS on human health. PFAS have been widely detected in drinking water worldwide and regulations have been developed, or are under development, in many countries. Drinking water quality standards describes
7938-418: The increased pressure can facilitate melting. Most importantly, τ D is increased. These factors will combine to accelerate the glacier. As friction increases with the square of velocity, faster motion will greatly increase frictional heating, with ensuing melting – which causes a positive feedback, increasing ice speed to a faster flow rate still: west Antarctic glaciers are known to reach velocities of up to
8036-423: The infrared OH stretching mode of the water molecule. (Liquid water appears blue for the same reason. The blue of glacier ice is sometimes misattributed to Rayleigh scattering of bubbles in the ice.) A glacier originates at a location called its glacier head and terminates at its glacier foot, snout, or terminus . Glaciers are broken into zones based on surface snowpack and melt conditions. The ablation zone
8134-420: The matter is resolved. The ability of point of use (POU) options to reduce disease is a function of both their ability to remove microbial pathogens if properly applied and such social factors as ease of use and cultural appropriateness. Technologies may generate more (or less) health benefit than their lab-based microbial removal performance would suggest. The current priority of the proponents of POU treatment
8232-679: The most deformation. Velocity increases inward toward the center line and upward, as the amount of deformation decreases. The highest flow velocities are found at the surface, representing the sum of the velocities of all the layers below. Because ice can flow faster where it is thicker, the rate of glacier-induced erosion is directly proportional to the thickness of overlying ice. Consequently, pre-glacial low hollows will be deepened and pre-existing topography will be amplified by glacial action, while nunataks , which protrude above ice sheets, barely erode at all – erosion has been estimated as 5 m per 1.2 million years. This explains, for example,
8330-445: The most sensitive indicators of climate change and are a major source of variations in sea level . A large piece of compressed ice, or a glacier, appears blue , as large quantities of water appear blue , because water molecules absorb other colors more efficiently than blue. The other reason for the blue color of glaciers is the lack of air bubbles. Air bubbles, which give a white color to ice, are squeezed out by pressure increasing
8428-725: The pooling of meltwater at the base of the glacier — perhaps delivered from a supraglacial lake — or the simple accumulation of mass beyond a critical "tipping point". Temporary rates up to 90 m (300 ft) per day have occurred when increased temperature or overlying pressure caused bottom ice to melt and water to accumulate beneath a glacier. In glaciated areas where the glacier moves faster than one km per year, glacial earthquakes occur. These are large scale earthquakes that have seismic magnitudes as high as 6.1. The number of glacial earthquakes in Greenland peaks every year in July, August, and September and increased rapidly in
8526-487: The presence of various metal ions , often rendering the water " soft " or " hard ". In the event of contamination of drinking water, government officials typically issue an advisory regarding water consumption. In the case of biological contamination , residents are usually advised to boil their water before consumption or to use bottled water as an alternative. In the case of chemical contamination , residents may be advised to refrain from consuming tap water entirely until
8624-410: The pressure of the layers of ice and snow above it, this granular ice fuses into denser firn. Over a period of years, layers of firn undergo further compaction and become glacial ice. Glacier ice is slightly more dense than ice formed from frozen water because glacier ice contains fewer trapped air bubbles. Glacial ice has a distinctive blue tint because it absorbs some red light due to an overtone of
8722-443: The quality parameters set for drinking water. Water may contain many harmful constituents , yet there are no universally recognized and accepted international standards for drinking water. Even where standards do exist, the permitted concentration of individual constituents may vary by as much as ten times from one set of standards to another. Many countries specify standards to be applied in their own country. In Europe, this includes
8820-567: The sea, often with an ice tongue , like Mertz Glacier . Tidewater glaciers are glaciers that terminate in the sea, including most glaciers flowing from Greenland, Antarctica, Baffin , Devon , and Ellesmere Islands in Canada, Southeast Alaska , and the Northern and Southern Patagonian Ice Fields . As the ice reaches the sea, pieces break off or calve, forming icebergs . Most tidewater glaciers calve above sea level, which often results in
8918-409: The stagnant ice above, forming a bergschrund . Bergschrunds resemble crevasses but are singular features at a glacier's margins. Crevasses make travel over glaciers hazardous, especially when they are hidden by fragile snow bridges . Below the equilibrium line, glacial meltwater is concentrated in stream channels. Meltwater can pool in proglacial lakes on top of a glacier or descend into the depths of
9016-423: The stress being applied, ice will act as an elastic solid. Ice needs to be at least 30 m (98 ft) thick to even start flowing, but once its thickness exceeds about 50 m (160 ft) (160 ft), stress on the layer above will exceeds the inter-layer binding strength, and then it'll move faster than the layer below. This means that small amounts of stress can result in a large amount of strain, causing
9114-438: The surface snowpack may experience seasonal melting. A subpolar glacier includes both temperate and polar ice, depending on the depth beneath the surface and position along the length of the glacier. In a similar way, the thermal regime of a glacier is often described by its basal temperature. A cold-based glacier is below freezing at the ice-ground interface and is thus frozen to the underlying substrate. A warm-based glacier
9212-437: The water provided by public water suppliers is for drinking and cooking. Uses include (in decreasing order) toilets, washing machines, showers, baths, faucets, and leaks. As of 2015, American households use an average of 300 gallons of water a day. The qualitative and quantitative aspects of drinking water requirements on domesticated animals are studied and described within the context of animal husbandry . For example,
9310-417: The weight of the ice is supported by the underlying water, and the glacier is afloat. Glaciers may also move by basal sliding , where the base of the glacier is lubricated by the presence of liquid water, reducing basal shear stress and allowing the glacier to slide over the terrain on which it sits. Meltwater may be produced by pressure-induced melting, friction or geothermal heat . The more variable
9408-480: The world, although it may be expensive, and the supply may not always be sustainable. Sources where drinking water is commonly obtained include springs , hyporheic zones and aquifers ( groundwater ), from rainwater harvesting , surface water (from rivers, streams, glaciers ), or desalinated seawater . For these water sources to be consumed safely, they must receive adequate water treatment and meet drinking water quality standards . An experimental source
9506-658: Was determined with the presence of coliform bacteria , a convenient marker for a class of harmful fecal pathogens . The presence of fecal coliforms (like E. Coli ) serves as an indication of contamination by sewage . Additional contaminants include protozoan oocysts such as Cryptosporidium sp. , Giardia lamblia , Legionella , and viruses (enteric). Microbial pathogenic parameters are typically of greatest concern because of their immediate health risk. Physical and chemical parameters include heavy metals , trace organic compounds , total suspended solids , and turbidity . Chemical parameters tend to pose more of
9604-553: Was used to build the gravity structure. Works continued throughout World War II , when the Nazi authorities also deployed foreign workers ( Fremdarbeiter ) and POWs to complete the facilities. After the war and the division into East and West Germany from 1949, the inner German Border ran straight through the site. The Border Troops of the German Democratic Republic had walls and barbed wire mounted on
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