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Topic Review
Tsunami
A tsunami (Japanese: 津波) (/(t)suːˈnɑːmi, (t)sʊˈ-/ (t)soo-NAH-mee, (t)suu- pronounced [tsɯnami]) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions (including detonations, landslides, glacier calvings, meteorite impacts and other disturbances) above or below water all have the potential to generate a tsunami. Unlike normal ocean waves, which are generated by wind, or tides, which are generated by the gravitational pull of the Moon and the Sun, a tsunami is generated by the displacement of water. Tsunami waves do not resemble normal undersea currents or sea waves because their wavelength is far longer. Rather than appearing as a breaking wave, a tsunami may instead initially resemble a rapidly rising tide. For this reason, it is often referred to as a tidal wave, although this usage is not favoured by the scientific community because it might give the false impression of a causal relationship between tides and tsunamis. Tsunamis generally consist of a series of waves, with periods ranging from minutes to hours, arriving in a so-called "wave train". Wave heights of tens of metres can be generated by large events. Although the impact of tsunamis is limited to coastal areas, their destructive power can be enormous, and they can affect entire ocean basins. The 2004 Indian Ocean tsunami was among the deadliest natural disasters in human history, with at least 230,000 people killed or missing in 14 countries bordering the Indian Ocean. The Ancient Greece historian Thucydides suggested in his 5th century BC History of the Peloponnesian War that tsunamis were related to submarine earthquakes, but the understanding of tsunamis remained slim until the 20th century and much remains unknown. Major areas of current research include determining why some large earthquakes do not generate tsunamis while other smaller ones do; accurately forecasting the passage of tsunamis across the oceans; and forecasting how tsunami waves interact with shorelines.
  • 4.2K
  • 02 Dec 2022
Topic Review
Ocean Planet
An ocean planet, ocean world, water world, aquaplanet or panthalassic planet is a type of terrestrial planet that contains a substantial amount of water either at its surface or subsurface. The term ocean world is also used sometimes for astronomical bodies with an ocean composed of a different fluid, such as lava (the case of Io), ammonia (in a eutectic mixture with water, as is likely the case of Titan's inner ocean) or hydrocarbons like on Titan's surface (which could be the most abundant kind of exosea). Earth is the only astronomical object known to have bodies of liquid water on its surface, although several exoplanets have been found with the right conditions to support liquid water. For exoplanets, current technology cannot directly observe liquid surface water, so atmospheric water vapor may be used as a proxy. The characteristics of ocean worlds—or ocean planets—provide clues to their history and the formation and evolution of the Solar System as a whole. Of additional interest is their potential to originate and host life.
  • 4.1K
  • 19 Oct 2022
Topic Review
Marine Isotope Stage
Marine isotope stages (MIS), marine oxygen-isotope stages, or oxygen isotope stages (OIS), are alternating warm and cool periods in the Earth's paleoclimate, deduced from oxygen isotope data reflecting changes in temperature derived from data from deep sea core samples. Working backwards from the present, which is MIS 1 in the scale, stages with even numbers have high levels of oxygen-18 and represent cold glacial periods, while the odd-numbered stages are lows in the oxygen-18 figures, representing warm interglacial intervals. The data are derived from pollen and foraminifera (plankton) remains in drilled marine sediment cores, sapropels, and other data that reflect historic climate; these are called proxies. The MIS timescale was developed from the pioneering work of Cesare Emiliani in the 1950s, and is now widely used in archaeology and other fields to express dating in the Quaternary period (the last 2.6 million years), as well as providing the fullest and best data for that period for paleoclimatology or the study of the early climate of the Earth, representing "the standard to which we correlate other Quaternary climate records". Emiliani's work in turn depended on Harold Urey's prediction in a paper of 1947 that the ratio between oxygen-18 and oxygen-16 isotopes in calcite, the main chemical component of the shells and other hard parts of a wide range of marine organisms, should vary depending on the prevailing water temperature in which the calcite was formed. Over 100 stages have been identified, currently going back some 6 million years, and the scale may in future reach back up to 15 mya. Some stages, in particular MIS 5, are divided into sub-stages, such as "MIS 5a", with 5 a, c, and e being warm and b and d cold. A numeric system for referring to "horizons" (events rather than periods) may also be used, with for example MIS 5.5 representing the peak point of MIS 5e, and 5.51, 5.52 etc. representing the peaks and troughs of the record at a still more detailed level. For more recent periods, increasingly precise resolution of timing continues to be developed.
  • 4.1K
  • 03 Nov 2022
Topic Review
Integrated Watershed Management
Human activities mostly impact the trend and direction of rainwater, groundwater, and other river basin resources in the watershed in Africa. These activities alter river flows and the quality of usable water supplies at both highlands and lowlands. A watershed is indeed a conserved area of land that collects rain, sleet and snow, and empties or penetrates groundwater sources.
  • 4.1K
  • 26 Jan 2022
Topic Review
Groundwater–Surface Water Interaction
Groundwater and surface water, though thought to be different entities in the past, are connected throughout the different landforms of the world. The interaction between groundwater and surface water (GW–SW) is responsible for a phenomenon like contaminant transport, and understanding it helps to estimate the effects of climate change, land use on chemical behavior, and the nature of water. 
  • 3.9K
  • 18 Apr 2023
Topic Review
Health Impact of Drying Aral Sea: One Health
Once one of the largest saline lakes, the Aral Sea, was recognized as a significant environmental disaster as the water level decreased dramatically. Water level decrease increases water salinity, affecting biodiversity. Exposed lake beds become the source for fine dust picked up by the dust storms and spread across a long distance, affecting people’s health in surrounding areas. 
  • 3.7K
  • 13 Apr 2022
Topic Review
PEC Reactors for Water/Wastewater Treatment
Now and in the coming years, how we use and treat water, greywater and wastewater will become more important. A suitably designed photoelectrocatalytic (PEC) reactor is one potential solution. The photoexcitation of suitable semiconducting materials in aqueous environments can lead to the production of reactive oxygen species (ROS). ROS can inactivate microorganisms and degrade a range of chemical compounds. In the case of heterogeneous photocatalysis, semiconducting materials may suffer from fast recombination of electron–hole pairs and require post-treatment to separate the photocatalyst when a suspension system is used. To reduce recombination and improve the rate of degradation, an externally applied electrical bias can be used where the semiconducting material is immobilised onto an electrically conducive support and connected to a counter electrode. These electrochemically assisted photocatalytic systems have been termed “photoelectrocatalytic” (PEC). The term is stated in the IUPAC Recommendations 2011 as “electrochemically assisted photocatalysis. The role of the photocatalyst is played by a photoelectrode, often a semiconductor”. A short description of photocatalysis is included as it can be beneficial for those unfamiliar with the topic, before moving onto PEC. This entry is adapted from https://doi.org/10.3390/w13091198
  • 3.6K
  • 20 Oct 2021
Topic Review
Cultural Eutrophication
Cultural eutrophication is when a flux of excess nutrients from human activity are added into a local run-off which in turns speeds up the natural eutrophication. This is caused by human activity. The problem became apparent once the green revolution and industrial revolution began in the last century. Phosphates and nitrates are the two main nutrients that cause cultural eutrophication as they enrich the water, allowing for aquatic plants such as algae to grow rapidly. Algae is prone to blooming into large quantities removing oxygen from the water generating anoxic conditions. This anoxic environment kills off any organisms in the water body and make it hard for terrestrial animals to gain access to the water for drinking. Increased competition for the added nutrients can cause potential disruption to entire ecosystems and food webs, as well as a loss of habitat and biodiversity of species. There are many ways in which nutrients are added through human activity, including, but not limited to: waste treatment plants, golf courses, fertilizing lawns, burning of fossil fuels and agricultural practices. Cultural eutrophication can occur in fresh water and salt water bodies, usually shallow waters are the most susceptible. In shallow lakes, sediments are frequently disturbed by wind-wave and resuspended, which result in huge nutrients release to overlying water As well the shallow areas are normally where the run-off reaches first and has less water to dilute the excess nutrients. This begins to cause many problems for the nearby wildlife as well as recreational activities for humans. Eutrophication restricts water use for fisheries, recreation, industry and drinking because of increased growth of undesirable algae and aquatic weeds and the oxygen shortages caused by their death and decomposition.
  • 3.5K
  • 19 Oct 2022
Topic Review
Bauxite Tailings
Bauxite tailings, also known as bauxite residue, red mud, red sludge, or alumina refinery residues (ARR), is a highly alkaline waste product composed mainly of iron oxide that is generated in the industrial production of alumina (aluminium oxide, the principal raw material used in the manufacture of aluminium metal and also widely used in the manufacture of ceramics, abrasives and refractories). It is important to differentiate between the alkaline waste generated in the Bayer process and the tailings generated during the mining of bauxite. This article specifically covers the alkaline waste generated when operating the Bayer process. The scale of production makes the waste product an important one, and issues with its storage are reviewed and every opportunity is explored to find uses for it. Over 95% of the alumina produced globally is through the Bayer process; for every tonne of alumina produced, approximately 1 to 1.5 tonnes of bauxite tailings/residue are also produced. Annual production of alumina in 2018 was approximately 126 million tonnes resulting in the generation of over 160 million tonnes of bauxite tailings/residue.
  • 3.5K
  • 02 Nov 2022
Topic Review
Photocatalytic Reactors Design
The photoreactors design and concepts vary based on the working regime (static or dynamic), photocatalyst morphology (powders or bulk) and volume.
  • 3.5K
  • 10 May 2021
Topic Review
Urban Wetlands
Wetlands are a critical part of natural environments that offer a wide range of ecosystem services. In urban areas, wetlands contribute to the livability of cities through improving the water quality, carbon sequestration, providing habitats for wildlife species, reducing the effects of urban heat islands, and creating recreation opportunities. 
  • 3.4K
  • 13 Jan 2022
Topic Review
Sustainable Water Resources Management in Saudi Arabia
Saudi Arabia is one of the most water-scarce nations in the world, with a huge demand-supply gap, and the situation is expected to worsen due to climate change. Conventional surface water resources are limited, while nonrenewable groundwater sources are depleted. To build a more resilient and sustainable water sector, the production of non-conventional water resources, specifically desalinated seawater and treated domestic wastewater, has steadily increased in recent years. As the country lacks perennial water resources, such as rivers or water bodies, it relies mainly on nonrenewable groundwater and desalinated water to meet its daily requirements. Although the government is attempting to regulate the agricultural sector, water consumption in agriculture remains relatively high. It presents an environmental challenge due to its heavy reliance on non-renewable groundwater resources. The anticipated increase in temperature and highly uncertain changes in the rainfall patterns in Saudi Arabia could lead to greater uncertainty when attempting to develop effective water resource management plans.
  • 3.4K
  • 22 Dec 2023
Topic Review
The Use of Green Laser in LiDAR Bathymetry
Bathymetric LiDAR technology is a technology used for simultaneous data acquisition regarding the morphology of the bottom of water reservoirs and the surrounding coastal zone, realized from the air, e.g., by plane or drone. Contrary to the air topographic LiDAR, which uses an infrared wavelength of 1064 nm, bathymetric LiDAR systems additionally use a green wavelength of 532 nm. The green laser can penetrate the water, which makes it possible to measure the depth of shallow water reservoirs, rivers, and coastal sea waters within three Secchi depths.
  • 3.3K
  • 13 Jan 2023
Topic Review
Microplastic Removal and Degradation Techniques
Plastics are a kind of synthetic or semisynthetic polymer that are made up of long chains of carbon atoms, and they may also have oxygen, nitrogen, or sulfur atoms attached to them. The majority of plastics are produced by factories that use fossil fuels. Microplastics are small particles of fragments and microfibers of plastic that have a diameter of less than 5 mm. Because of the widespread usage of microbeads in a variety of goods as well as the fragmentation of plastics with increasing age, the quantity of microplastic released in the aquatic environment is alarming, and so effluent water needs to be treated in wastewater plants to remove the microplastics. Different biotic and abiotic approaches have been studied in different research over the years.
  • 3.2K
  • 23 Dec 2022
Topic Review
GeoAI in Integrated Hydrological and Fluvial Systems Modeling
Geospatial artificial intelligence (GeoAI) allows the harnessing of big and high-dimensional data to better understand the hydrological processes in a particular system. Specifically, GeoAI provides new data analytic tools to the entire data processing cycle, such as sensor data fusion, hydrological modeling, data assimilation, multi-objective scenario optimization, smart decision support, evaluation of climate change impact, construction of early warning systems, and geo-visualization. 
  • 3.2K
  • 22 Jul 2022
Topic Review
Measurement and Monitoring of TDS and TSS
Total dissolved solids (TDS) and total suspended solids (TSS) have traditionally been analyzed and monitored through field or in situ sampling and laboratory testing generally classified as conventional methods. Field and laboratory measurements include grab sampling, filtering, and evaporating a sample through a fine filter paper followed by drying in an air oven which are collectively known as gravimetric methods. Conventional methods of monitoring of water quality parameters (WQPs) are, however, cost-prohibitive, labor-intensive, time-consuming, and, also not suitable for large-scale analysis.
  • 3.2K
  • 21 Jul 2023
Topic Review
On-Site Carwash Wastewater Treatment
The main pollutants in car wash wastewater are detergents, dirt, oil, and grease. Untreated wastewater released into rainwater sewer systems or other water bodies may pollute the water and generate excessive bubble foams, which negatively affects urban appearance. Car washes are divided into mechanical car washes and manual or self-service car washes. In general, car washes have a small operation and scale, occupy limited land, and cannot afford wastewater treatment costs. Therefore, most car washes are not equipped with wastewater treatment facilities. Consequently, the discharge of wastewater from car washes negatively affects the water quality in the surrounding environment and results in wasteful use of water resources. 
  • 3.2K
  • 22 Jun 2022
Topic Review
Grey Water
Grey water (also spelled gray water in the United States) or sullage refers to wastewater generated in households or office buildings from streams without fecal contamination, i.e., all streams except for the wastewater from toilets. Sources of grey water include sinks, showers, baths, washing machines or dishwashers. As grey water contains fewer pathogens than domestic wastewater, it is generally safer to handle and easier to treat and reuse onsite for toilet flushing, landscape or crop irrigation, and other non-potable uses. The application of grey water reuse in urban water systems provides substantial benefits for both the water supply subsystem, by reducing the demand for fresh clean water, and the wastewater subsystems by reducing the amount of wastewater required to be conveyed and treated. Treated grey water has many uses, for example, toilet flushing or irrigation.
  • 3.2K
  • 04 Nov 2022
Topic Review
Stepwells as Sustainable Water Management Structures
Stepwells were one such effective water management technologies used in India. Stepwells were constructed based on their geographical and topographical suitability, which revealed socio-cultural behaviors and beliefs.
  • 3.2K
  • 28 Sep 2022
Topic Review
Computer-Vision-Based Water Level Measurement
Water level measurement is an important component of hydrological monitoring and water resources management. Information such as runoff, water supply volumes and flood discharge is usually calculated based on water level measurement. To alleviate the problems associated with manual and contact measurements, the computer-vision-based approaches rely on the automatic acquisition and analysis of water surface images. Images allow the capture of water surfaces without interruption to provide insight into the continuous change of water level. Computer vision can automatically acquire and understand the meaningful information in images, such as the scope of water surface area, water line, gauge characters, etc., to obtain faster recognition speed and more accurate and stable results than human in the water level measurement task.
  • 3.1K
  • 26 Sep 2023
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