Changes in water location, availability, temperature, purity and salinitythe degree to which something is salty can produce additional climate and weather changes, flooding, droughts, disruption in the natural balances of plants and animal species and the spread of diseases.

If all of Earth's water, located in oceans, icecaps and glaciers, lakes, rivers, groundwater and water in the atmosphere, were put into a sphere, the diameter of that water ball would be about 860 miles (about 1,385 km), a little more than the distance between Salt Lake City, Utah and Topeka, Kansas. The volume of all water would be about 332.5 miles³, or 1,386 km³.^[1]

A mile³ of water equals more than 1.1 trillion gallons. A km³ of water equals about 264 billion gallons, or 1 trillion liters.^[1]

About 3,100 mile³ (12,900 km³) of water, mostly in the form of water vapor, is in the atmosphere. If it all fell as precipitation at once, the Earth would be covered with only about 1 inch of water.^[1]

Each day, the lower 48 U.S. states receive a total volume of about 4 mile³ (17.7 km³) of precipitation and 280 mile³ (1,170 km³) of water evaporate or transpire into the atmosphere.^[1]

If all of the world's water was poured on the contiguous U.S. states, it would cover the land to a depth of about 107 miles (145 km).^[1]

Of the fresh water on Earth, more is stored in the ground than is available in rivers and lakes. More than 2,000,000 mile³ (8,400,000 km³) of fresh water is stored in the Earth, most within one-half mile of the surface. Most fresh water is stored in the 7,000,000 mile³ (29,200,000 km³) of glaciers and icecaps in the polar regions and in Greenland.^[1]

Sources:

 
Ice Sheets

An ice sheet forms through snowfall accumulation, when annual snowfall exceeds annual snowmelt. Snow layers build up for thousands of years, creating a flowing ice sheet thousands of meters thick. Increasing snow height puts pressure on the layers below, which deform and spread out in all directions.^[1]

Earth's two ice sheetsa mass of glacial land ice extending more than 50,000 square kilometers (20,000 square miles) cover most of Greenland and Antarctica. They contain more than 99% of Earth's fresh water ice.^[1]

Due to increased carbon emissions and global warming they are now melting six times faster than in the 1990s, the worst-case climate warming scenario set out by the Intergovernmental Panel on Climate Change (IPCC). In the near future melting ice could produce a sea level rise that could leave 400 million people living near coasts subject to major flooding.^[3]

Average annual Greenland and Antarctica ice loss in the 2010s was 475 billion tons, six times greater than the 81 billion tons lost each year during the 1990s. Between 1992 and 2017, the two ice caps lost 6.4 trillion tons of ice, 60% from Greenland, and the remaining 40% from Antarctica.^[3]

In 2022, Greenland experienced its largest September melting event, due to global warming. The first day of September marks the end of the Greenland melt season, as the Sun appears to move lower in the sky, causing decreasing temperatures.^[4]

But warm air moved over Baffin Bay,
Baffin Bay
Connormah
Jun. 12, 2009
Wikipedia Baffin Bay
https://en.wikipedia.org/
wiki/Baffin_Bay#/media/
File:Baffin_Bay,_Canada.svg
CC BY-SA 3.0 resulting in tens of billions of tons of lost ice. Parts of western Greenland experienced 35^oF (20^oC) temperatures. About 35% of the ice was affected, far above the usual 10% for September. During the event, Greenland may have lost about 20 billion tons of ice, about 7% of the annual total ice loss.^[4]

Meltwater runoff rates were as high as 12 billion tons per day, one of the top ten largest runoff events on record. If it refreezes, it creates ice sheets that prevent meltwater from percolating through snowpack, contributing to sea level rise. For every 360 billion tons of ice lost, sea level rises about 1 millimeter. Greenland is the largest contributor to that rise.^[4]

In the past, scientists found four liquid lakes below the Greenland ice sheet, but 50 more have recently been located. There are about 470 lakes beneath Antarctica.

The largest, Lake Vostok,
Satellite view of Lake Vostok
Goddard Spaceflight Center/NASA
May 23, 2005
Wikipedia Lake Vostok
https://en.wikipedia.org/
wiki/Lake_Vostok#/media/
File:Lake_Vostok_Sat_Photo_color.jpg
public domain is 250 kilometers long. The biggest subglacial lake under Greenland is only 6 kilometers in length.^[5]

Water pools under ice sheets due to ice pressure from above and geothermal heat from below which keeps the water in liquid form. Melting surface water also drains into subsurface lakes.^[5]

Scientists study these lakes and their interaction with the ice sheets to determine how they are affected by global warming and how they will contribute to rising sea levels.^[5] If all of Greenland's ice melts, it will increase global ocean height by 7 meters.^[5]

Sources:

 
Arctic Region

Most of the Arctic consists of liquid saltwater of the Arctic ocean basin. Some parts of the ocean's surface remain frozen all year as sea ice which may be covered in snow. Sea ice affects Earth's climate by reflecting about 80% of the light that strikes it.^[2]

Following sunset on the September equinox,when the Sun appears directly above the equator, rising due east and setting due west, around March 20 and September 23 the Earth's axial tiltthe 23^o tilt of Earth's axis relative to the plane of its orbit around the Sun and revolutionrefers to Earth's orbit around the Sun of approximately 365 days, 6 hours, 9 minutes around the sun reduce the light and heat reaching the Arctic until no sunlight penetrates the darkness.^[2]

The sun rises again during the March equinox and increases the light and heat reaching the Arctic. By the June solsticeoccurs when the Sun appears to reach its most northerly, around June 21, or southerly, around December 21, positions relative to the celestial equator on the celestial sphere the Arctic experiences 24 hours of daylight.^[2]

The Arctic includes the Bering, Beaufort and Chukchi seas, and sea ice, coastal wetlands, upland tundra,a vast, flat, treeless Arctic region of Europe, Asia and North America in which the subsoil is permanently frozen mountains, wide rivers. About 4 million people from several cultures live in the Arctic, parts of which belong to 8 different countries.^[1]

Frozen Arctic soil holds about 1,460 to 1,600 billion tons of trapped carbon, about twice the amount in the atmosphere.^[3]

Greenhouse gases from fossil fuel burning is causing temperatures in the Arctic to warm at twice the rate of the rest of the world.^[2] Methanea powerful greenhouse gas and the simplest hydrocarbon, consisting of one carbon atom and four hydrogen atoms and carbon are found in Arctic permafrost,thick subsurface layer of soil that remains frozen throughout the year, usually in polar regions frozen peat bogs and under sea floor sediment. As they thaw, methane and carbon are released into the atmosphere, adding more global greenhouse gases and global warming. More warming results in more permafrost loss and more atmospheric greenhouse gases.^[3]

What happens in the Arctic has an effect on wildfires in the western U.S. Ice loss causes land and sea surface warming, resulting in hotter and drier summers subjected to fire-related conditions.^[4]

Arctic Ocean ice helps regulate global land and sea temperatures. White sea ice reflects about 50 to 70% of solar radiation, preventing Earth from getting warmer.^[3]

Disappearing sea ice also exposes the darker ocean surface. The ocean reflects only 6% of solar radiation, absorbing the rest and warming water and surrounding atmosphere. The disappearance of this ice is moving toward an irreversible tipping point. Within the next 20 to 25 years, there may be no sea ice in September in the Arctic.^[3]

Fossil fuels also increase the acidity of Arctic water, harming zooplankton,plankton consisting of small animals and the immature stages of larger animals which are the base of the Arctic food chain.^[1]

The decrease in volume and extent of Arctic sea ice has serious implications for the habitat of polar and brown bears, several whale species, ringed seals, Arctic wolves, Pacific salmon, porpoises and dolphins that live on Arctic land and the surrounding sea.^[2]

The reduction in sea ice has warmed Alaska's climate, accelerated coastal erosion, reduced walrus and other marine mammal habitat, changed the timing and location of microscopic plant life and lowered survival rates for some fish species.^[3]

Sources:

 
Antarctic Region

The ice sheet contains approximately 7 million cubic miles (about 29 million cubic km) of ice, representing about 90% of the world's ice and 80% of its fresh water. Its average thickness is about 5,900 feet (1,800 m).^[1]

Ice shelves cover parts of the Ross and Weddell seas. The Ross Ice Shelf, the Filchner-Ronne Ice Shelf and other continental margin shelves create the border of about 45% of the continent. Around the coast, shelves, glaciers and ice sheets release icebergs into the seas.^[1]

Scientific investigation began during the 1957-58 International Geophysical Year (IGY). On December 1, 1959, the 12 countries active in Antarctica during the IGY signed the Antarctic Treaty, preserving the continent for nonmilitary scientific pursuits and placing Antarctica under an international regime binding members to review of its provisions after 30 years. The treaty placed the boundary at 60^o south latitude.^[1]

The 1991 Madrid Protocol prohibited mining, required environmental impact assessments for new activities, and designated the continent as a natural reserve.^[1]

Scientists have mapped the continent's mountain regions, and until the 1970s relied on ground-based seismic surveys to find mountain ranges and peaks. Airborne radio-echo sounding systemsa transmitter and receiver system that sends out radio waves and detects those waves bounced from objects now measure ice-thickness, facilitating systematic surveys.^[1]

An underwater robot called Icefin deployed beneath the Thwaites ice shelf and confirmed that it is one of the least stable ice shelves in Antarctica. Researchers estimate that its collapse could lead to a two-foot rise in sea level over the next few centuries. Thwaites contributes about 4% to current overall rate of global sea level rise, about 1.5 inches per decade.^[2]

Fresh water melting ice could slow currents by as much as 40% in the next 30 years by reducing ocean salinity. Slower currents deliver less oxygen, carbon dioxide and nutrients to the world's marine ecosystem and warmer water can't absorb as much atmospheric carbon dioxide as in the past.^[3]

Deeper and warmer water creates a positive environmental feedback loop.accelerates an environmental response, such as increasing ice melting rates or raising global temperatures More melting releases more fresh water into the oceans, affecting rainfall and agriculture.^[3]

Sources:

 
Glaciers

Glaciers, made from compressed snow that develops into thick ice masses, have been melting since the early 1900s and 95% of the oldest and thickest ice in the Arctic has disappeared.^[5]

About 10% of Earth's surface is covered by glaciers, most of which are located in Antarctica, Greenland, and the Canadian Arctic. Most glaciers were formed during the Little Ice Ageclimate cooling period that occurred from the early 14th century through the mid-19th century, when mountain glaciers expanded at several locations, including the European Alps, New Zealand, Alaska, and the southern Andes, and mean annual temperatures across the Northern Hemisphere declined by 0.6C^o when ice covered about 32% of Earth's land area, and 30% of the oceans.^[1]

There are several types of glaciers: calving,a glacier that ends in a body of water into which it drops icebergs cirque,a small glacier that forms in a basin high on the side of a mountain hanging,a glacier that begins high on a glacier valley wall and descends only part of the way to the surface of the main glacier piedmont,a fan or lobe-shaped glacier, located at the front of a mountain range polar,a glacier in which ice temperatures always remain below the freezing point reconstituteda glacier formed below the bottom of a hanging glacier by the accumulation, and reconstitution by pressure melting of ice blocks that have fallenor avalanched from the end of the hanging glacier rock,a glacier-like landform that consists of a valley-filling accumulation of angular rock blocks, has little or no visible surface ice temperate,a glacier in which liquid water coexists with glacier ice during part or even all of the year tidewatera glacier that ends in a body of water influenced by tides, such as the ocean or a large lake and valley.a glacier that flows for all or most of its length within the walls of a mountain valley, also called an alpine glacier or a mountain glacier^[2]

Glacier facts:

• glacial ice often appears blue when it has become dense and bubble-free due to compression
• white glacial ice indicates trapped air bubbles
• the Bering glacier
  Bering glacier
  NASA
  Sep. 29, 2002
  Wikipedia Bering glacier
  https://en.wikipedia.org/
  wiki/Bering_Glacier#/media/
  File:Bering_glacier.jpg
  public domain in Alaska, measuring 190 kilometers is North America's longest glacier
• the record for the fastest glacial surge belongs to Kutiah Lungma glacier
  Kutiah Lungma glacier
  A. Rizmi
  Aug. 16, 2012
  Wikipedia Kutiah Lungma glacier
  https://en.wikipedia.org/
  wiki/Kutiah_Lungma_Glacier#/media/
  File:Kutia_Lungma_Glacier.jpgCC BY-SA 4.0
  in Pakistan which moved more than 12 kilometers in three months during 1953
• Washington state has more glaciers than any other U.S. state, and they provide 1.8 trillion liters (470 billion gallons) of water every summer
• the world's largest glacier is the Lambert glacier
  Lambert glacier
  NASA/USGS
  Dec. 2, 2000
  Wikipedia Lambert glacier
  https://en.wikipedia.org/
  wiki/Lambert_Glacier#/media/
  File:Icefall_hires_2.jpg
  public domain
  in Antarctica, which is 400 kilometers (250 miles) long, and up to 100 kilometers (60 miles) wide.^[3]

Global warming is having a significant effect on Earth's glaciers:

• the snows of Kilimanjaro
  Kilimanjaro
  Chris 73
  Mar. 16, 2007
  Wikipedia Kilimanjaro
  https://en.wikipedia.org/
  wiki/Mount_Kilimanjaro#/media/
  File:Mt._Kilimanjaro_12.2006.JPG
  CC BY-SA 3.0 have melted more than 80 percent since 1912



• glaciers in the Garhwal Himalaya in India are retreating so fast that researchers believe that most central and eastern Himalayan glaciers could virtually disappear by 2035
• spring fresh water ice breakup in the Northern Hemisphere now occurs nine days earlier than it did 150 years ago, and autumn freeze-up ten days later
• thawing permafrost has caused the ground to subside more than 15 feet (4.6 meters) in parts of Alaska
• glaciers from the Arctic to Peru, from Switzerland to the equatorial Man Jaya in Indonesia, are quickly disappearing.^[4]

The number of glacial lake outburst floodsa flood caused by the failure of a dam containing a glacial lake has increased significantly since 1990, affecting nearly 15 million people. About 1 million residents of High Mountains Asia live within 10 kilometers of a glacial lake, with more than half living in India, Pakistan, Peru and China.^[7]

While white snow is Earth's most reflective surface, pink algae, found at high altitudes on glaciers, forms what scientists call watermelon snow. This pink snow absorbs heat, forcing snow to melt quickly, leaving large pools of red water. Scientists are studying how this algae, Chlamydomonas nivalis, affects seasonal water supplies and its potential impact on flooding and how climate change may alter the algal growth.^[6]

Sources:

 
Oceans, Seas, Currents

Earth has 5 major oceans: Pacifichome to the Mariana trench, the deepest oceanic trench on Earth, measuring about 2,550 kilometers (1,580 miles) in length and 69 kilometers (43 miles) in width.^[1], Atlanticthe breakup of Pangaea created the Atlantic Ocean^[2], Indianthe smallest and geographically youngest ocean^[3], Southernwater cooled by cold air, outgoing radiation, and katabatic winds off of the Antarctic continent sinks and flows northward along the ocean bottom and replaced at the surface by warmer water flowing south from the Indian, Pacific, and Atlantic oceans^[4] and Arcticalmost completely circled by North America, Eurasia, and Greenland^[5] that are all part of a global ocean.

The Pacific contains the Middle America trench
Middle America trench
U.S. Government
Mar. 8, 2006
Wikipedia Middle America trench
https://en.wikipedia.org/
wiki/Middle_America_Trench#/media/
File:MiddleAmericaTrench.jpg
public domain located off the west coast of Central Ameica. It extends northwest-southeast for more than 1,700 miles (2,750 km) from central Mexico to Costa Rica. The trench reaches a maximum depth of 21,880 feet (6,669 m) and covers a total area of 37,000 square miles (96,000 square km).^[23]

The Peru-Chile trench,
Peru-Chile trench
U.S. Government
Mar. 7, 2006
Wikipedia Peru-Chile trench
https://en.wikipedia.org/
wiki/Peru%E2%80%93Chile_Trench#/media/
File:Peru-Chile_trench.jpg
public domain also called Atacama Trench, is a submarine trench in the eastern Pacific Ocean, about 100 miles (160 km) from the Peru and Chile coast. It reaches a maximum depth of 26,460 feet (8,065 m) below sea level in Richards Deep and is approximately 3,666 miles (5,900 km) long. It covers about 228,000 square miles (590,000 square km).^[24]

The Mariana trench
Mariana trench
Kmusser
Aug. 7, 2007
Wikipedia Mariana trench
https://en.wikipedia.org/wiki/
Mariana_Trench#/media/File:
Marianatrenchmap.png
CC BY 2.5 is located in the western North Pacific.^[21] It is about 35, 876 feet (10, 935 m) deep. It was designated a U.S. national monument in 2009.^[22]

More than 70% of Earth's surface is covered by water. The deepest known ocean depth is nearly 11,000 m (36,000 feet or almost 7 miles).^[11] Scientists estimate the hydrospherethe combined mass of water found on, under, and above Earth`s surface contains about 1.36 billion cubic kilometers of water. The second most common form of the water molecule on our planet is ice. If all of Earth's ice melted, sea-level would rise by about 70 meters.^[6]

Ocean currents, which can flow for thousands of kilometers, are generated by Earth's rotation, the wind, temperature gradients,an increase or decrease in the magnitude of a physical property salinitythe degree to which something is salty variations, density and the gravitational influence of the Moon. Ocean depths, shorelines, and other currents affect current strength, direction and speed. Currents influence climate.^[7]

The Gulf Stream,
Gulf Stream
Sommerstoffel
May 24, 2006
Wikipedia Gulf Stream
https://en.wikipedia.org/
wiki/Gulf_Stream#/media/
File:Golfstrom.jpg
public domain for example, makes northwest Europe much more temperate than any other region at the same latitude.^[7]

Thermohalinerelating to the effects of temperature and salinity circulation produces conveyor-belt like motion in deep ocean density-driven currents called submarine rivers.a river-like current on the seabed ^[7]

Studies have suggested that one of the world's largest currents, the Atlantic Meridional Overturning Circulation (AMOC),
Atlantic Meridional Overturning Circulation (AMOC)
C. Lee
Oct. 30, 2021
Wikipedia Atlantic meridional overturning circulation
https://upload.wikimedia.org/
wikipedia/commons/a/ab/
Thermohaline_circulation.svg
CC BY-SA 4.0 is slowing down due to global warming. The AMOC helps move heat between the equator and the Arctic. It also regulates climate and weather patterns in the Northern Hemisphere. Some scientists have warned that this current may disappear.^[12]

There are five major gyres:large systems of rotating currents the North and South Pacific Subtropical gyres, the North and South Atlantic Subtropical gyres, and the Indian Ocean Subtropical gyre.^[9]

The 1958 Convention on the High Seas established that the high seas were open to all nations for freedom of navigation, freedom of fishing, freedom to lay submarine cables and pipelines and freedom to fly over the high seas. The convention also addressed safety, warships, piracy and pursuit.^[26]

The 1982 Law of the Sea Conventionoff (LOSC) established a legal framework for the use and protection of natural and cultural resources of the sea, the seabed and subsoil and the marine environment. The LOSC includes clear guidelines on states' navigational rights, maritime zones and boundaries and economic jurisdiction. It also provides international cooperation and dispute resolution guidelines. The U.S. is not a party to the LOSC but follows it. The treaty has not obtain sufficient Congressional support needed for U.S. accession.^[25]

In April 2023 a new U.N. high seas treaty was written to address rules that have failed to prevent fishery depletion, loss of fragile habitats, decline of whale, sea turtle and bird populations and other marine life and ambiguities and lack of cooperation between entities claiming to have legal jurisdiction. It would also establish marine protected areas (MPAs).areas that include marine sanctuaries, estuarine research reserves, ocean parks and marine wildlife refuges^[27]

According to the U.S. Department of Energy ocean tides and river currents generate a small fraction of U.S. electricity today, but have the the potential to account for about 8% of U.S. power generation in the future.^[15]

The U.N. Environmental Program estimated that each year, about 11 million tons of plastic end up in the oceans. Approximately 300 million tons of plastic waste, equal to the weight of the world's human population, are produced every year. About 9% is recycled. The rest accumulates in landfills and the environment.^[13]

The Great Pacific Garbage Patch, about the size of Texas, is a Pacific Ocean zone between Hawaii and California with a high plastic waste concentration. Garbage from the west coast of the U.S. and east coast of Japan is carried by the California current, the North Equatorial current, the North Pacific current, and the Kuroshio current to the North Pacific subtropical gyre, the clockwise rotation of which draws in and traps solid matter including plastics.^[8]

The ocean's plastic problems have been known since the late 1980s. In 2015 and 2016, Ocean Cleanup discovered that the garbage patch plastic density was more than expected and that the plastics absorbed pollutants, making them poisonous to marine life.^[8]

Scientists discovered that garbage patch plastics are providing a home for coastal species in the open ocean. Some of these species, including bryzoans,a non-moving aquatic invertebrate of the phylum Bryozoa which comprises of the moss animals jellyfish, sponges and worms, are reproducing in their new and alien environments along with open ocean species. Future research may determine whether these coastal and open ocean species are competing or cooperating.^[19]

The International Coastal Cleanup® began more than 35 years ago, with coastal Texas community working together to collect and document coastal litter. Local and state volunteers in the U.S. and more than 150 countries participate in a cleanup events.^[14]

In March 2023 scientists found more than 13 million tons of Sargassumbrown algae with leafy segments, air bladders or spore-bearing structures drifting in the Atlantic Ocean. The seaweed is washing up on beaches in southwest Florida and Mexico.^[20]

Larger than usual mats were first identified in 2011. Scientists speculate that nutrient-rich runoff from the Congo, Amazon and Mississippi Rivers is encouraging algae growth. When Sarassum reaches the shore it decomposes, degrades water quality, pollutes beaches and produces hydrogen sulfide.gaseous substance found in several inorganic water pollutant such as electric power waste, oil and gas extraction operations waste, sewage treatment plants, large pig farms and other confined animal feeding operations, Portland cement kilns, municipal waste landfills, coke ovens, sulfur products, asphalt production and storage and geothermal power plants^[20]

Oceanic basins consist of continental shelves,a portion of a continent that is submerged under an area of relatively shallow water continental slopes,the slope between the outer edge of the continental shelf and the deep ocean floor abyssal plains,an underwater plain on the deep ocean floor abyssal hills,a hill that rises from the sea floor seamounts,a large ocean mountain that does not rise above the sea surface ocean trenches,a long, narrow depression in the ocean floor volcanic islandsan island created from volcanic eruptions^[10] and six zones:

• epipelagic zone,the upper open ocean, where there is enough sunlight for algae to utilize photosynthesis, from the sea surface down to approximately 200 m (650 feet) home to whales and dolphins, billfishes, tunas, jellyfishes, sharks and other creatures, algae that live in this zone are responsible for much of the original food production for the entire ocean and create at least 50% of the oxygen in the atmosphere
• mesopelagic zone,middle open ocean, from the bottom of the epipelagic to the point where sunlight can't reach, approximately 1000 m (3300 feet) deep the most numerous vertebrates on Earth live in this zone and migrate up into shallower, epipelagic depths to feed at night
• bathypelagic zone,lower open ocean, starts at the bottom of the mesopelagic and stretches down to 4000 m (13,000 feet) much larger than mesopelagic, 15 times the size of the epipelagic, largest Earth ecosystem, upper bound defined by lack of sunlight, organisms live in darkness which can be interrupted by light emitted by the organisms through bioluminescencebiochemical emission of light by living organisms such as fireflies and deep-sea fish used to attract prey or to find a mate
• abyssopelagic zone,from the bottom of the bathypelagic to the seafloor, characterized by a relative lack of life from the bottom of the bathypelagic to the seafloor, characterized by a relative lack of life
• hadopelagic zone,where deep, wide trenches occur in the flat seafloor where deep, wide trenches occur in the flat seafloor
• benthos zonewhere organisms live on the ocean floor include coral reefs, seagrass beds, and other systems in shallow coastal areas and deep hydrothermal vents, the abyssal plain, and other systems in the deep sea.^[11]

Territorial seas are coastal ocean waters subject to the jurisdiction of coastal nations that extend up to 12 nautical milesunit used in measuring distances at sea equal to approximately 2,025 yards or 1,852 meters from shore. These seas:

• make up about 6% of the sea and 22 million square kilometers of territorial waters
• are home to 83% of the world's coral reefs, 100% of its mangroves and sea grasses
• are home to the highest concentration of biodiversity related to human needs
• are used by 492 million people, about 7% of humanity
• received 0.01% of global philanthropic funding in 2020.^[18]

Sources:

 
Rivers

A river forms when water moves from uphill at a higher elevation to downhill, at a lower elevation, because of gravity. Small creeks and streams frequently merge to form rivers, most of which flow into oceans.^[1]

Rivers contain fresh water,characterized by having low concentrations of dissolved salts and other total dissolved solids and all of the world's rivers carry about 3.6 billion metric tons of salt from land to the ocean each year.^[2]

River water sources include melting glaciers, like the Gangotri glacier
Gangotri glacier
P. Basak
Sep. 8, 2015
Wikipedia Gangotri glacier
https://en.wikipedia.org/
wiki/Gangotri_Glacier#/media/File:
Gomukh_the_source_of_Ganga.jpg
CC BY-SA 4.0 the source of the Ganges River in Asia. The snows of the Andes feed the Amazon River. A river's source could be a lake with an outflowing stream, such as Lake Itasca
Lake Itasca Mississippi source
C. Karim
May 25, 2004
Wikipedia Lake Itasca
https://en.wikipedia.org/
wiki/Lake_Itasca#/media/File:
Lake_Itasca_Mississippi_Source.jpg
CC BY-SA 3.0 in Minnesota, as the source of the Mississippi River. The source of the Danube River
Danube River in Budapest
Visions of Domino
Jul. 5, 2016
Wikipedia Danube River
https://en.wikipedia.org/
wiki/Danube#/media/
File:View_from_Gell%C3%A9rt_
Hill_to_the_Danube,_Hungary
_-_Budapest_(28493220635).jpg
CC BY-SA 2.0 is a spring in the Black Forest of Germany.^[5]

Rivers can form estuaries,the tidal mouth of a large river, where the tide meets the stream and large sources of brackish water.having more salinity than fresh water, but not as much as seawater

Many cities were established around rivers, which were used primarily for irrigation, drinking water, and waste disposal, and later for power generation.^[1]

Only 17% of rivers are free-flowing and within protected areas. Freshwater species have declined by 84% since 1970 as a result of river degradation. Free-flowing rivers sustain diverse ecosystems and food chains, provide drinking water and serve as cultural sites for billions of people.^[8]

An Oregon State University study concluded that in the past 20 to 30 years 70% of fish species in Japanese and New Zealand rivers were threatened or endangered. Poor living conditions for fish and insects exist in 50% of European, 44% of U.S., 25% of South Korea and 30% of Australian rivers.^[9]

Water resources managers and scientists explore ways to restore natural river environments without further flood damage. One of the solutions involves controlled water release from reservoirsa large natural or artificial lake used as a source of water supply to reconstruct natural flood patterns.^[3]

The Amazon carries more water than any other river on Earth and about one-fifth of all fresh water to the oceans.^[5]

The Mississippi River is North America's largest, connecting the Ohio River to the east and Missouri River to the west.^[3] In October 2022, low water levels in the Mississippi backed up about 3,000 barges. The river and its tributaries transport more than $17 billion of farm products.^[6]

Some states fed by Mississippi water are developing new ways to deal with decreasing water, including low-impact hydropower, naturally moving sediments to restore water habitats and utilizing satellite images to create three dimensional measurements of water levels and distribution.^[6]

American Rivers called on governors in Iowa, Illinois, Missouri, Minnesota and Wisconsin to fund the Keys to the River 2020: An Upper Mississippi River Flood Risk, Sediment and Drought Study completed by the Army Corps of Engineers.^[7]

Redlining,refusing a loan or insurance to someone because they live in an area deemed to be a poor financial risk economic injustice and leveean earthen barrier along a stream, lake or river that protects the surrounding land from flooding failures disproportionally affect low income communities which are often left out of decision-making processes aimed at economic growth, rather than human impacts.^[7]

In 2023, the American Rivers list, based on river significance to people and wildlife, river threats and public influence, had changed.

The U.S. and Canada share the Columbia River and the St. Lawrence River. In the Pacific Northwest, the Columbia and its dams comprise the world's largest hydropower system, and those dams have caused contention between salmon fisheries and dam operators. The boundary between eastern Canada and the U.S. is formed by the St. Lawrence, which flows into the Atlantic Ocean.^[3]

In the southwestern U.S., the Colorado River flows through arid and highly populated regions, providing water to millions of people. This river has been so dammed and diverted that it no longer reaches its previous mouth, and now ends, dried up in the Mexican desert. Environmental groups are developing strategies for restoring the Colorado to its previous conditions.^[3]

Rivers have played major roles in history, transportation, warfare, culture and geography. Civilizations have grown around river deltas, where food could be easily grown and traded.

 
Lakes

Lakes are created when large basins are filled with water. Basins have been formed by glaciers during ice ages, and dams that were created by rocks and debris left behind. The lakes in Minnesota, "The Land of 10,000 Lakes," and the Great Lakes were created by glaciers.^[1] Most of these lakes, including the Great Lakes, are often hundreds of meters deep.^[3]

Both the Caspian Sea
Caspian Sea
J. Schmaltz, MODIS Rapid Response Team/NASA
Jun. 11, 2003
Wikipedia Caspian sea
https://en.wikipedia.org/
wiki/Caspian_Sea#/media/File:
Caspian_Sea_from_orbit.jpg
public domain and Lake Baikal
Lake Baikal
J. Descloitres, MODIS Land Rapid Response Team, NASA
Oct. 23, 2001
Wikipedia Lake Baikal
https://en.wikipedia.org/
wiki/Lake_Baikal#/media/File:
Baikal.A2001296.0420.250m-NASA.jpg
public domain were formed by plate tectonics which created faults, natural lake basins.^[1] Baikal is the world's oldest and deepest fresh water lake, and more water than all of the Great Lakes combined.^[3]

Crater Lake
Crater Lake in Winter
WolfmanSF
Nov. 14, 2012
Wikipedia Crater Lake
https://en.wikipedia.org/
wiki/Crater_Lake#/media/File:
Crater_Lake_winter_pano2.jpg
CC BY-SA 3.0

Some lakes are created by rivers forming meanders.a river following a winding course The lake left behind is called an oxbow lake.a curved lake formed where the main stream of a river has cut across the narrow end and no longer flows around the loop of the bend^[1]

Lakes can also be created by landslides or mudslides, creating piles of debris blocking the flows of streams. Beavers also create natural dams out of tree branches can plug up rivers or streams and make large ponds or marshes.^[1]

Most lakes contain fresh water, but some lakes become saline when their waters cannot combine with other fresh water lakes and rivers. Some of these lakes were formed when they were connected to seas, but they have been shrinking since the last ice age. Lake Bonneville,
Lake Bonneville
Steplinin
May 1, 2019
Wikipedia Lake Bonneville
https://en.wikipedia.org/
wiki/Lake_Bonneville#/media/File:
Image_of_Lake_Bonneville
_shorelines.png
public domain an ancient U.S. lake, was once as big as Lake Michigan, and the Great Salt Lake
Great Salt Lake
J. Morris
Dec. 16, 2008
Wikipedia Great Salt Lake
https://en.wikipedia.org/
wiki/Great_Salt_Lake#/media/
File:Great_Salt_Lake_Map.jpg
CC BY-SA 3.0
was once about 14 times larger than it is now, and it is saltier than the oceans.^[3]

Most lakes support a lot of aquatic life, but life is rarer in salty lakes. The Dead Sea
Dead sea halite deposits
Wilson44691
Mar. 17, 2012
Wikipedia Dead Sea
https://en.wikipedia.org/
wiki/Dead_Sea#/media/File:
Dead_Sea_Halite_View_031712.jpg
CC BY-SA 3.0 in the Middle East is too salty to support aquatic life.^[3]

The Aral Sea,
Aral Sea
Shannon1
Aug. 10, 2017
Wikipedia Aral Sea
https://en.wikipedia.org/
wiki/Aral_Sea#/media/
File:Aral_Sea_watershed.png
CC BY-SA 4.0 located in Central Asia, is one of the world's largest inland water bodies. in the second half of the 20th century its area was reduced by two-fifths and its level dropped by more than 12 meters, because of the diversion of the Syr Darya
Syr Darya
Shannon1
Feb. 5, 2010
Wikipedia Syr Darya
https://en.wikipedia.org/
wiki/Syr_Darya#/media/
File:Syrdaryamap.png
CC BY-SA 4.0 and Amu Darya
Amu Darya
J. Pyrek
Feb. 10, 2010
Wikipedia Amu Darya
https://en.wikipedia.org/
wiki/Amu_Darya#/media/
File:Amudaryasunset.jpg
CC BY-SA 2.0
rivers, for field irrigation.^[2]

Some lakes, like the Chad Basin
Chad Basin
Sting and Aymatth2
May 6, 2013
Wikipedia Chad Basin
https://en.wikipedia.org/
wiki/#/media/File:Chad_River_
Basin_relief_2.png
CC BY-SA 3.0 in Africa, have no outflow. Their levels rise and fall based on local climate conditions and water usage.^[2]

Lakes serve as recreational scenic sites. Their water is an important natural resource. They serve as habitats for aquatic and wildlife.^[2]

Lake ecosystems are easily affected by their environments, including the purity of local groundwater and human activities, which can be mitigated if those affects are identified. Nutrients, including fertilizer phosphorousa poisonous, combustible nonmetal which exists as white phosphorus, a yellowish waxy solid which ignites spontaneously in air and glows in the dark, and red phosphorus, a less reactive form used in making matches and nitrogena colorless, odorless unreactive gas that forms about 78% of Earth's atmosphere can significantly affect algae growth, producing bacteria.

Many cities have human-made lakes in parks.^[3] Water quality in those lakes need to be continuously monitored and maintained because humans and their pets drink, swim in, sail, and kayak in those waters.

Precipitation refers to water released from clouds in the form of rain, freezing rain, sleet, snow or hail. It is the primary connection in the water cycle that provides for the delivery of atmospheric water to the Earth. Most precipitation falls as rain.^[1]

Weather and humidity are related. Warm air can hold more water vapor than cool air. This means that if a parcelan air bubble that keeps its shape as it rises or sinks in the atmosphere of cool air and a parcel of warm air have the same amount of water vapor, the cool parcel has a higher relative humiditythe amount of water vapor present in air as a percentage of the amount needed for atmospheric saturation at the same temperature than the warm parcel.^[10]

Upper atmosphere moisture cools quickly, forming large clouds that spread under low pressure conditions. Rapid upward air flow from Earth's surface creates low-pressure areas near the ground. Cool air fills the low pressure areas, producing precipitation.^[11]

Clouds contain water vapor and cloud droplets, small drops of condensed water. The droplets are too small to fall as precipitation, but large enough to form visible clouds, which continuously evaporate and condense. Most of the condensed water doesn't fall as precipitation because the fall speed isn't high enough to overcome cloud updrafts.upward air movement^[1]

The first stage in precipitation occurs when tiny water droplets adhere to condensation nuclei,tiny suspended particles, either solid or liquid, upon which water vapor condensation begins in the atmosphere which serve as the basis for raindrops.^[1]

If the particles grow large enough, they produce raindrops with fall velocities which exceed cloud updraft speeds. Millions of tiny cloud droplets are needed to produce a single raindrop.^[1]

Another more efficient mechanism is known as the Wegener-Bergeron-Findeisen process,a process of ice crystal growth that occurs in mixed phase clouds which leads to the rapid growth of ice crystals using water vapor in clouds. These crystals may fall as snow, or melt and fall as rain.^[1]

SO₂sulfur dioxide + OHhydroxide ➔ HOSO₂hydroxysulfonyl radical

HOSO₂hydroxysulfonyl radical + O₂oxygen ➔ HO₂water + SO₃sulfur trioxide

SO₃ (g)sulfur trioxide gas + H₂O (l)water ➔ H₂SO₄ (aq)sulfuric acid

NO₂nitrogen dioxide + OHhydroxide ➔ HNO₃nitric acid

Small amounts of sulfur dioxide and nitrogen oxides come from erupting volcanoes, but most is the result of burning fossil fuels by electric power generators, vehicles, manufacturing, oil refineries and other industries.^[8]

Acid rain water leachesdrain away from soil, ash or other material by water aluminum from soil particles which flow into streams and lakes. Some plants and animals can tolerate acidic waters and moderate amounts of aluminum, but others can't live in low pHused to specify how acidic or alkaline a water-based solution is, acidic solutions have lower pH, and alkaline solutions have higher pH conditions. At pH 5 most fish eggs cannot hatch, frogs can't survive below pH 4 and the mayflies frogs eat don't survive below ph 5.5.^[9]

Acid rain also kills trees, other plants and animals because it removes soil minerals and nutrients required for growth.^[9]

At high elevations, acid foga thick cloud of tiny water droplets suspended in the atmosphere near Earth's surface and clouds remove nutrients from trees, leaving them with brown or dead leaves and needles. Unable to absorb sunlight, the trees are weakened and less able to withstand freezing temperatures.^[9]

Melting snow and heavy rain can cause episodic acidification, creating short-term ecosystem stress.^[9]

Acid rain causes coastal water nitrogen pollution, partially responsible for declining fish and shellfish populations.^[9]

South Asia's monsoonsa seasonal change in prevailing wind direction that often results in weeks or months of rainy weather begin on India's west coast, with spring wind changes that push moist air from the Arabian Sea
Arabian Sea
NASA/MODIS
Oct. 12, 2012
Wikipedia Arabian Sea
https://en.wikipedia.org/
wiki/Arabian_Sea#/media/File:
Arabian_Sea_-_October_2012.jpg
public domain toward land.^[6]

Some farms experience temporary droughts, while others get too much rain, too quickly. In 2022, monsoon rains in Pakistan left much of the country underwater and killed more than 1,500 people. In India's technology capital, Bengaluru, September monsoon rains required workers to commute by boat.^[6]

To counteract the effects of climate change villagers dug long trenches by hand along hillsides to catch rain. The trenches prevent rain from running into streams. Instead, the water flows into local wells, providing a water supply after the monsoons have ended.^[6]

In most years, Pacific winter storms deliver about 48 cubic miles of mountain snow, which remains frozen until the spring. During hot and dry months, melted snow flows into rivers, lakes, reservoirs and underground aquifers. Twenty-five million people depend on this water for irrigation, food and hydroelectric power.^[7]

In 2015 California experienced a dry snow drought, when a high-pressure air mass called a ridiculously resilient ridgelarge high-pressure mass that remains over the U.S. West Coast for prolonged periods and that diverts storms winter storms, intensifying drough blocked winter snow storms, leaving only 25% of normal snowfall, and creating the state's worst recorded snow drought.^[7]

Washington and Oregon experienced a wet snow drought. The Pacific Northwest had a relatively wet winter in 2015, but warm temperatures produced rain, rather than snow. Water that would have melted during the spring flowed directly into rivers, lakes and streams, and was no longer available during hot, dry months.^[7]

Fog is found in coastal zones around the planet. Its most noticeable human impact is on transportation, because shipping, road traffic and air travel and freight delays cost billions of dollars per year.^[2]

But fog is also essential for plants and animals and agriculture and human health.

Along Chile's coast, cold ocean water rises to the surface carrying nutrients to wave tops where they form fog droplet nuclei that condense and then floats over land. Fog transports these nutrients from the ocean to the forests.^[2]

Fog is the main source of moisture in the Namib Desert in Southwest Africa where it sustains vegetation providing metabolic fuel for 48 species, including the tenebrionid beetle Tenebrionid darkling beetle at Dar es Salaam, Tanzania
M. M. Karim
Jan. 1, 2009
Wikipedia darkling beetle
https://en.wikipedia.org/
wiki/Darkling_beetle#/media/
File:Darkling_beetle.jpg
GNU Free Documentation License 1.2 that captures and drinks fog.^[2]

Plant material and decomposition matter provide water best when they have been wet, which usually will be from fog^[5]

While persistent fog can destroy food crops, it can benefit others, including artichoke and pumpkin fields in California's central coast, where fog creates the right light, temperature and moisture conditions for crop growth.^[2]

America's most famous fog occurs in California, near the Golden Gate Bridge.^[2] In June, July and August, most of the Northern Hemisphere, including California, endures high summer temperatures. But the average daily high in San Francisco is below 70^oF (21^oC), cooler than any major continental U.S. city.^[3]

Anecdotal evidence from shoreline residents and scientists idicate that fog along that state's coast and the Santa Cruz region is diminishing. The reasons for the decline aren't clear, but climate change and increasing temperatures may explain why the fog, sustaining California's redwoods, is slowly disappearing. Redwoods and Torrey pines are showing signs of distress.^[2]

One study demonstrated that fog has decreased about 30% in the past 60 years along the west coast. In the 1950s, coastal California got about 12 hours of fog per day during fog season. That has now been reduced to about 9 hours per day.^[2]

Fog also reduces air temperature. One study that analyzed reduced fog showed a disproportionately high number of excessive heat deaths in coastal zones when fog is reduced. Those used to cooler temperatures because of fog may not know how to prepare themselves to deal with excess heat.^[2]

Studies in Sao Paulo and Los Angeles demonstrate that human emissions produced fog near industrial centers. Pollution control efforts have reduced this reflective fog loaded with industrial pollution, which is more reflective than clean haze. The reduction of smog allows more warming, further diminishing fog.^[2]

Icy fog, called pogonipa dense winter fog containing frozen particles that is formed in deep mountain valleys of the western U.S. by the Shoshone, forms in some high valleys of the Western U.S. This fog forms only in conditions cold enough to threaten respiratory health. Indigenous people and settlers recognized and feared this fog.^[2]

Water harvested from fog is becoming increasingly important for people in arid, subtropical areas that are drying out with global warming.^[2]

These forests and special plant communities might be the most vulnerable because rising temperatures could quickly push their fog belt upward, exposing sensitive cloud forests with many species that can only survive in fog zones.^[2]

Fog nets can capture between 200 and 400 liters of fresh water per day, providing a reliable water source. More than 2,000 have been installed across Peru, Bolivia, Colombia and Mexico. Fog collected in the Peruvian provinces of Cusco, Tacna and Arequipa is clean, and the water it creates can be used by humans.^[4]

In 2009, German conservationists planted she-oak trees in Peru to create a natural fog-catching system to replicate ancient water-capturing methods that collected water dripping from fog-covered plants. In Lima, Peru, one of the world's most polluted cities, fog nets pick up pollution. The condensed water can be used for crops and animals, but not for human consumption.^[4]

In Morocco, lack of water has affected rural Amazigh communities, creating a daily burden for women, who spent more than three hours per day carrying water from communal wells to their homes. They now use fog nets. Similar fog harvesting successes have helped residents of Namibia, Bolivia and Chile.^[4]

Water purification techniques may make polluted fog water fit to drink. Fog collection may provide reliable water for drought-stricken communities. But while new technologies are being brought to bear on the problem the basic techniques of fog catching go back centuries.^[4]

Sources:

 
Groundwater

Water in aquifersa body of permeable rock which can contain or transmit groundwater reaches the surface through springs, is discharged into lakes and streams, or extracted from man-made or artesian wells. In areas where material above the aquifer is permeable, pollutants can readily sink into groundwater supplies.^[1]

Groundwater is used for drinking by more than 50% of the U.S. population, but the most substantial use of groundwater is crop irrigation.^[1]

In some areas of the world people face serious water shortages because groundwater is used faster than it can be recharged. In other areas groundwater is polluted by human activities related to landfills, septic tanks,a tank used to hold domestic water wastes leaky underground gas tanks and from overuse of fertilizers and pesticides. If groundwater becomes polluted, it will no longer be safe to drink.^[1]

Some of the substances introduced into groundwater include antimony,a lustrous gray metalloid, found in nature mainly as the sulfide mineral stibnite arsenic,a solid chemical element that is used especially in wood preservatives, alloys, and semiconductors and is extremely toxic in both pure and combined forms cadmium,a soft, malleable, bluish white metal found in zinc ores chromium,a blue-white metallic element found naturally only in combination and used especially in alloys and in electroplating copper,a highly conductive metallic chemical element that is easily formed into sheets and wires cyanide,a large group of poisonous chemical compounds used to make plastics and to extract and treat metals lead,a soft, dense, malleable metal with a relatively low melting point mercury,a silver-white poisonous heavy metallic element that is liquid at ordinary temperatures used in batteries, in dental amalgam, and in scientific instruments nitrate,usually combined with sodium or potassium and used as a fertilizer nitrite,a salt or ester of nitrous acid silver,a malleable, polishable, metallic chemical element, has the highest thermal and electric conductivity of any substance, used in jewelry, tableware, electronics, and as an antimicrobial and sulfatea salt of sulfuric acid, containing the anion SO from a variety of industrial processes. Others, including aluminum,a silver-white malleable, conductive, light metallic chemical element that resists weathering, and is the most common metal in Earth's crust barium,a silver-white metallic element used in drilling fluid and vacuum tubes, and as a contrast agent in medical imaging beryllium,a steel-gray, light, brittle chemical element that occurs naturally in beryl used as a hardening agent in alloys iron,a strong, hard magnetic silvery-gray metal used as a material for construction and manufacturing, especially in the form of steel manganese,a grayish-white, hard, brittle metallic element that resembles iron but is not magnetic and is used in alloys, batteries, and plant fertilizers nickel,a silver-white hard malleable, ductile, metallic element capable of a high polish and resistant to corrosion used in alloys and as a catalyst selenium,a photosensitive element that occurs in crystalline and amorphous forms, obtained as a by-product in copper refining, used in glass, semiconductor devices and alloys sodium,a silver-white, soft, waxy, ductile, chemically-active element that occurs abundantly in nature thalliuma soft poisonous metallic element that physically resembles lead, occurs sparsely in a number of common ores, used in the form of compounds especially in photosensitive devices and zinca bluish-white, ductile metallic element when pure and heated, brittle at ordinary temperatures, an essential micronutrient for both plants and animals, used especially in alloys and as a protective coating in galvanizing iron and steel occur naturally and mix with groundwater.^[2]

Sources:

 
Weather Events

El Niño has a significant affect on weather. The warmer waters cause the Pacific jet streama narrow band of strong westerly air currents that circles the Earth several miles above its surface to move southward, resulting in warmer and dryer areas in the northern U.S. and Canada. In the U.S. Gulf Coast and Southeast El Niño produces wetter weather and flooding.^[1]

El Niño also affects Pacific coast marine life. During normal conditions, upwelling brings water from the deep ocean to the surface. This water provides a lot of nutrients but during El Niño upwelling weakens or stops, decreasing phytoplanktonplankton consisting of microscopic plants populations off the coast, affecting fish that serve as part of the food chain.^[1]

El Niño is characterized by

• average sea surface temperatures in the equatorial Pacific Oceandefined by latitudes between 5^oN and 5^oS and longitudes between 120^oW and 170^oW were at least 0.5^oC (0.9^oF) warmer than average in the preceding month
• the anomaly persisted or is expected to persist for 5 consecutive, overlapping 3-month periods, for example December, January and February or January, February and March or February, March and April
• the atmosphere over the tropical Pacific exhibits one or more of the changes commonly associated with El Niño including weaker than usual easterly trade winds, reduced cloudiness and rainfall over Indonesia and a corresponding increase in the average surface pressure or increased cloudiness and rainfall in central or eastern part of the basin and a corresponding drop in the average surface pressure.^[3]

This cold water in the Pacific pushes the jet stream northward, leading to lead to drought in the southern U.S. and heavy rains and flooding in the Pacific Northwest and Canada.^[1]

During a La Niña year, winter temperatures are warmer than normal in the South and cooler than normal in the North. La Niña can also lead to a more severe hurricane season.^[1]

La Niña is characterized by

• average sea surface temperatures in the equatorial Pacific Oceandefined by latitudes between 5^oN and 5^oS and longitudes between 120^oW and 170^oW cooler than average in the preceding month
• an average anomaly of at least -0.5^oC has persisted or is expected to persist for 5 consecutive, overlapping 3-month periods, for example December, January and February or January, February and March or February, March and April
• the atmosphere over the tropical Pacific exhibits changes commonly associated with La Niña, including stronger than usual easterly trade winds, an increase in cloudiness and rainfall over Indonesia and a corresponding drop in average surface pressure, a decrease in cloudiness and rainfall in the eastern tropical Pacific and an increase in the average surface pressure.^[3]

Over the last 50 years oceans have absorbed more than 90% of the heat generated by human-produced global warming. Rising sea level temperatures increase hurricane energy, slow atmospheric circulation, and cause hurricanes to move more slowly over land.^[2]

Sources:

 
Drought

Global drought frequency and duration increased by about a third since 2000. More than 2.3 billion people around the world are currently facing water stress.^[1]

More than 10 million have died due to major drought events over the past 100 years. By 2050 drought could affect more than 75% of the world's population.^[2] As many as 5.7 billion people could live in areas with water shortages for at least one month a year and more than 215 million people could be displaced from their homes.^[1]

Women who carry out agricultural responsibilities are often not recognized as farmers. This limits their income and technology and ability to access sustainability practices.^[4]

Some women have been successful. In India, women developed an underground rainwater catchment system. In Benin, West Africa, a solar power system irrigates fields so women don't have to collect and transport water from rivers and aquifers.^[4]

Drought has been declared in parts of England. The first six months of 2022 were the driest since 1976. The National Drought Group estimates that by 2050 some rivers could have only 20% of their current water supplies. Temperatures could increase by 7C^o due to climate change. (Degree changes are noted as C^o or F^o while specific temperatures are noted as ^oC or ^oF.) In July 2022, U.K. temperatures were above 40^oC for the first time.^[1]

The Italian government declared a state of emergency in five regions in July 2022 because of a drought, the worst in 70 years. About a third of Italy's 17 million citizens live around the Po River, with more than half of the nation's pigs and cattle. The drought has threatened olive oil and risotto rice supplies, significantly raising their prices.^[1]

France is experiencing its worst drought since in 1958, and is dealing with national water use restrictions. The country's corn harvest is expected to be 20% lower than in 2021.^[1]

Portugal recorded its hottest July ever, with 99% of the country suffering severe or extreme drought. Average temperatures were just over 40^oC, almost three degrees higher than the usual July average.^[1]

The Netherlands is one of the world's flattest and most densely populated countries, and the world's second leadeing exporter of farm products. Climate change has produced hot, dry summers, reducing fresh water Alpine snowmelt that normally flows into the Rhine River. As less fresh water flows down the Rhine toward the North Sea, seawater moves landward, toward clean home and farm water supplies.^[17]

In August 2022, the Rhine's flow was at a record low, forcing farmers in Enshede to illegally siphon water from ponds. As a result, city planners approved construction of ditches in grassy areas to catch rainwater. Concrete tiles and other paved surfaces were removed to expose water-absorbing soil and brooks and streams were reshaped reduce runoff.^[17]

Some Dutch water boards have been helping growers dry out fields since the Middle Ages. Now they are assisting farmers in keeping their land wet by using efficient drip irrigation.^[17]

Around 75% of Romania is affected by drought. The country's cereal crop is expected to decrease by 30 million metric tons.^[1]

• the percentage of plants affected by drought has more than doubled in the last 40 years, with about 12 million hectares of land lost each year due to drought and desertification^[11]
• ecosystems turn into carbon sources, especially during droughts, and have been located on five continents^[12]
• rapid increases in surface temperature correlate with declining biodiversity and higher extinction rates^[13],[14]
• in 2019 and 2020, the Australian megadrought created megafires and massive habitat loss^[15]
• between 2000 and 2010, the Amazon experienced three widespread droughts, triggering forest fires.^[16]

• proactive measures can reduce risks and increase resilience of ecosystems and communities via sustainable land management and ecosystem restoration^[5]
• in the last 20 years, Nigerian farmers have reduced drought risks by creating new agroforestry systems on 5 million hectares over 20 years^[6]
• Colombian farmers created an ecological restoration-based education program that produced 71 novel nursery gardens and 400,000 seedlings of 21 native forest species^[7]
• a 2017 California case study showed that an increase of about 100 drought stories over two months was associated with a reduction of 11% to 18% percent in typical household water-use^[8]
• limiting global warming to 1.5C^o, along with regenerative land and improved water management practices, is expected to reduce extreme drought events^[9]
• a paradigm shift from reactive and crisis-based approaches to proactive and risk-based drought management approaches.^[10]

Sources:

 
Floods

According to the National Climate Assessment, rain intensity increased significantly between 1958 and 2016. For each Celsius degree increase in Earth's temperature, the amount of atmospheric water vapor increases by around 7%.^[1]

Floods occur when a lot of rain falls quickly and cannot soak into the ground because of saturation or impermeability.not allowing liquid or gas to go through Water pools on land surfaces or flows downhill, creating destructive and often deadly flash floods.^[1]

Floods alter landscapes, erode riverbanks, increase sedimentation, clog rivers, displace and smother fish and other aquatic life when their habitats are washed away.^[3]

Floodwater can be contaminated with agricultural pesticides, industrial chemicals, debris and sewage. Floods are the primary cause of weather-related infectious disease outbreaks, increasing the chance of spreading waterborne diseases including hepatitis Aa highly contagious liver infection caused by the hepatitis A virus and cholera.an intestinal infection caused by Vibrio cholerae bacteria^[3]

Receding floodwater creates stagnant water pools leaving a breeding ground for mosquitoes, which can transmit malaria.a serious and sometimes fatal disease caused by a mosquito parasite Flood events also lead to an increase in some forms of zoonosisa disease which can be transmitted to humans from animals, such as leptospirosisan infectious bacterial disease that occurs in rodents, dogs, and other mammals and can be transmitted to humans.^[3]

Researchers calculated that floods also affect the U.S. housing market. They found that residential properties at risk of flooding were overvalued by between $121 billion and $127 billion. Most were found in coastal counties with no flood risk disclosure laws, in those where there was little concern about climate change, in low-income communities and in cities and towns highly dependent on property taxes.^[4]

Floods replenish underground water sources. Floodwater is absorbed by the ground, percolating through soil and rock, reaching underground aquifers, which supply clean fresh water to springs, wells, lakes and rivers.^[3]

Small seasonal floods help native fish outcompete invasive species. Sediment deposited during floods serves as fish nurseries for small fish, and the nutrients they bring support aquatic food webs by boosting productivity.^[3]

Approximately 40% of world species rely on wetlands, which filter water, mitigate flooding and act as carbon sinks. The Okavango Delta in Botswana is a UNESCO World Heritage Site and one of the world's largest, most important wetland habitats. The river captures rainfall from the Angolan highlands, causing flooding that replenishes wetlands during the dry season, providing a Kalahari Desert oasis.^[3]

Floods can trigger breeding events and migration. In 2016, thousands of water birds flocked to the Macquarie Marshes in New South Wales, Australia. Flooding had filled their wetland habitat for the first time in years, triggering a mass breeding event.^[3]

In Cambodia, monsoon rains cause the annual Mekong River flood pulse migration. The floodwaters caused the Tonle Sap river, connecting to the Mekong River to Tonle Sap lake, to reverse its flow. Floodwater entering the lake starts fish migrations, supporting one of the world's most productive fisheries.^[3]

Coastal flooding results from coastal storms, including hurricanes or nor'eastersa storm that travels along the Eastern Seaboard and brings winds from the northeast that create destructive storm surges, walls of water moving from ocean onto land.^[2]

Higher sea level produces shallow floods known as nuisance or sunny day floods. These floods wash over roads and into storm drains during high tide.^[2]

Urban flooding refers to flooding that occurs when rainfall, rather than a body of water, exceeds stormwater drain capacity, usually in densely populated areas.^[2]

Because the National Weather Service issues flood watches and warnings, local weather services can notify citizens and the media.^[1]

Flooding can be mitigated by undeveloped land areas, forests, wetlands and retention ponds.^[1]

Sources:

 
Resources

Denise Meeks, dmeeks@arizona.edu