Earth’s hydrosphere

In physical geography, the term hydrosphere (Greek hydro means "water") describes the collective mass of water found on, under, and over a planet's surface. The Earth's hydrosphere consists chiefly of the oceans, but technically includes clouds, inland seas, lakes, rivers, and underground waters.

The abundance of water on Earth is a unique feature that distinguishes our "blue planet" from others in the solar system. Approximately 70.8 percent of the Earth is covered by water and only 29.2 percent is terra firma. The average depth of the Earth's oceans is 3,794 m (12,447 ft)—more than five times the average height of the continents. The mass of the oceans is approximately 1.35 × 1018 tons, or about 1/4400 of the total mass of the Earth.

The hydrosphere plays a key role in the development and sustenance of life. It is thought that the earliest living organisms probably emerged in a watery soup. In addition, each human life begins in the watery environment of its mother's womb, our cells and tissues are mostly water, and most of the chemical reactions that are part of life's processes take place in water.

WATER CYCLE

WATER CYCLE

The water cycle, or the hydrologic cycle, is the continuous circulation of water within the Earth's hydrosphere. It involves the movement of water into and out of various reservoirs, including the atmosphere, land, surface water, and groundwater. This cycle is driven by radiation from the Sun. The movement of water within the water cycle is the subject of the field of hydrology.

The water moves from one reservoir to another, such as from river to ocean, or from the ocean to the atmosphere, by the physical processes of evaporation, condensation, precipitation, infiltration, runoff, and subsurface flow. In so doing, the water goes through different phases: liquid, solid, and gas.

The water cycle also involves the exchange of heat energy, which leads to temperature changes. For instance, in the process of evaporation, water takes up energy from the surroundings and cools the environment. Conversely, in the process of condensation, water releases energy to its surroundings, warming the environment.

The water cycle figures significantly in the maintenance of life and ecosystems on Earth. Even as water in each reservoir plays an important role, the water cycle brings added significance to the presence of water on our planet. By transferring water from one reservoir to another, the water cycle purifies water, replenishes the land with freshwater, and transports minerals to different parts of the globe. It is also involved in reshaping the geological features of the Earth, through such processes as erosion and sedimentation. In addition, as the water cycle involves heat exchange, it exerts an influence on climate as well.

Movement of water within the water cycle

There is no definable start or finish to the water cycle. Water molecules move continuously among different compartments, or reservoirs, of the Earth's hydrosphere, by different physical processes. Water evaporates from the oceans, forms clouds, which precipitate and the water falls back to Earth. However, water does not necessarily cycle through each compartment in order. Before reaching the ocean, water may have evaporated, condensed, precipitated, and become runoff multiple times.

WATER POLLUTION

Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans and groundwater). Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds.

Water pollution affects plants and organisms living in these bodies of water; and, in almost all cases the effect is damaging not only to individual species and populations, but also to the natural biological communities.

Water pollution is a major global problem. It has been suggested that it is the leading worldwide cause of deaths and diseases,[1][2] and that it accounts for the deaths of more than 14,000 people daily.[2] An estimated 700 million Indians have no access to a proper toilet, and 1,000 Indian children die of diarrheal sickness every day.[3] Some 90% of China's cities suffer from some degree of water pollution,[4] and nearly 500 million people lack access to safe drinking water.[5] In addition to the acute problems of water pollution in developing countries, industrialized countries continue to struggle with pollution problems as well. In the most recent national report on water quality in the United States, 45 percent of assessed stream miles, 47 percent of assessed lake acres, and 32 percent of assessed bay and estuarine square miles were classified as polluted.

Groundwater pollution

Interactions between groundwater and surface water are complex. Consequently, groundwater pollution, sometimes referred to as groundwater contamination, is not as easily classified as surface water pollution.[7] By its very nature, groundwater aquifers are susceptible to contamination from sources that may not directly affect surface water bodies, and the distinction of point vs. non-point source may be irrelevant. A spill or ongoing releases of chemical or radionuclide contaminants into soil (located away from a surface water body) may not create point source or non-point source pollution, but can contaminate the aquifer below, defined as a toxin plume. The movement of the plume, called a plume front, may be analyzed through a hydrological transport model or groundwater model. Analysis of groundwater contamination may focus on the soil characteristics and site geology, hydrogeology, hydrology, and the nature of the contaminants.

CAUSES OF POLLUTION

The specific contaminants leading to pollution in water include a wide spectrum of chemicals, pathogens, and physical or sensory changes such as elevated temperature and discoloration. While many of the chemicals and substances that are regulated may be naturally occurring (calcium, sodium, iron, manganese, etc.) the concentration is often the key in determining what is a natural component of water, and what is a contaminant. High concentrations of naturally-occurring substances can have negative impacts on aquatic flora and fauna.

Oxygen-depleting substances may be natural materials, such as plant matter (e.g. leaves and grass) as well as man-made chemicals. Other natural and anthropogenic substances may cause turbidity (cloudiness) which blocks light and disrupts plant growth, and clogs the gills of some fish species.[10]

Many of the chemical substances are toxic. Pathogens can produce waterborne diseases in either human or animal hosts.[11] Alteration of water's physical chemistry includes acidity (change in pH), electrical conductivity, temperature, and eutrophication. Eutrophication is an increase in the concentration of chemical nutrients in an ecosystem to an extent that increases in the primary productivity of the ecosystem. Depending on the degree of eutrophication, subsequent negative environmental effects such as anoxia (oxygen depletion) and severe reductions in water quality may occur, affecting fish and other animal populations.

Many causes of pollution including sewage and fertilizers contain nutrients such as nitrates and phosphates.  In excess levels, nutrients over stimulate the growth of aquatic plants and algae.  Excessive growth of these types of organisms consequently clogs our waterways, use up dissolved oxygen as they decompose, and block light to deeper waters. This, in turn, proves very harmful to aquatic organisms as it affects the respiration ability or fish and other invertebrates that reside in water.      Pollution is also caused when silt and other suspended solids, such as soil, wash off plowed fields, construction and logging sites, urban areas, and eroded river banks when it rains.  Under natural conditions, lakes, rivers, and other water bodies undergo Eutrophication, an aging process that slowly fills in the water body with sediment and organic matter. 

When these sediments enter various bodies of water, fish respiration becomes impaired, plant productivity and water depth become reduced, and aquatic organisms and their environments become suffocated.  Pollution in the form of organic material enters waterways in many different forms as sewage, as leaves and grass clippings, or as runoff from livestock feedlots and pastures.  When natural bacteria and protozoan in the water break down this organic material, they begin to use up the oxygen dissolved in the water.  Many types of fish and bottom-dwelling animals cannot survive when levels of dissolved oxygen drop below two to five parts per million.  When this occurs, it kills aquatic organisms in large numbers which leads to disruptions in the food chain.

Images of Water pollution

Water Pollution in The Philippines

A century ago the Pasig River in the Philippines was a place of beauty. The water was clean and teeming with life. It provided food and an income to Manila’s fishermen and was the transportation artery of the capital. Today the river is a place to avoid. The river's banks are covered with squatters’ huts. The water is pitch black and choked with rubbish. The Philippine Government has passed a Clean Air Act and Clean Water Act, but there is no budget available to implement either. Peter Coppen reports from Manila.

ADDITIONAL FORMS OF WATER POLLUTION

Three last forms of water pollution exist in the forms of petroleum, radioactive substances, and heat.  Petroleum often pollutes water bodies in the form of oil, resulting from oil spills.  The previously mentioned Exxon Valdez is an example of this type of water pollution.  These large-scale accidental discharges of petroleum are an important cause of pollution along shore lines.

Besides the supertankers, off-shore drilling operations contribute a large share of pollution.  One estimate is that one ton of oil is spilled for every million tons of oil transported.  This is equal to about 0.0001 percent. Radioactive substances are produced in the form of waste from nuclear power plants, and from the industrial, medical, and scientific use of radioactive materials. 

Specific forms of waste are uranium and thorium mining and refining.  The last form of water pollution is heat.  Heat is a pollutant because increased temperatures result in the deaths of many aquatic organisms.  These decreases in temperatures are caused when a discharge of cooling water by factories and power plants occurs.

 CLASSIFYING WATER POLLUTION

  The major sources of water pollution can be classified as municipal, industrial, and agricultural.  Municipal water pollution consists of waste water from homes and commercial establishments.  For many years, the main goal of treating municipal wastewater was simply to reduce its content of suspended solids, oxygen-demanding materials, dissolved inorganic compounds, and harmful bacteria.  In recent years, however, more stress has been placed on improving means of disposal of the solid residues from the municipal treatment processes. 

The basic methods of treating municipal wastewater fall into three stages: primary treatment, including grit removal, screening, grinding, and sedimentation; secondary treatment, which entails oxidation of dissolved organic matter by means of using biologically active sludge, which is then filtered off; and tertiary treatment, in which advanced biological methods of nitrogen removal and chemical and physical methods such as granular filtration and activated carbon absorption are employed.  The handling and disposal of solid residues can account for 25 to 50 percent of the capital and operational costs of a treatment plant.  The characteristics of industrial waste waters can differ considerably both within and among industries. 

The impact of industrial discharges depends not only on their collective characteristics, such as biochemical oxygen demand and the amount of suspended solids, but also on their content of specific inorganic and organic substances. Three options are available in controlling industrial wastewater.  Control can take place at the point of generation in the plant; wastewater can be pretreated for discharge to municipal treatment sources; or wastewater can be treated completely at the plant and either reused or discharged directly into receiving waters.

‘Water pollution a threat’

Gov’t not enforcing environment laws -- SWS survey

MANILA, Philippines – Five of every 10 Filipinos believe water pollution is a serious threat to their health and environment, but the government is unable to enforce environmental laws.

Results of a survey of the Social Weather Stations released Friday also showed that at least three of every six residents of Metro Manila did not agree that pollution was an “acceptable” trade-off for economic progress.

The SWS survey, a first on water pollution and enforcement of environmental laws, was commissioned by the environmental group Greenpeace as part of its “Project: Clean Water” program launched in September. The initiative aims to mobilize action in protecting the country’s vast fresh water sources.

A recent World Bank study warned of a possible water scarcity problem in the country by 2025.

The survey from Nov. 30 to Dec. 3 covered 1,200 randomly chosen adult respondents divided into samples of 300 each in Metro Manila, Luzon, Visayas and Mindanao.

“We wanted to see how Filipinos perceive the problem because it is very hard to push for the implementation of environmental laws if the public accepts water pollution as an unavoidable consequence of economic development,” said Beau Baconguis, Greenpeace Southeast Asia campaigner in a press conference Friday.

Half of the respondents said water pollution in the country was a “very serious” problem and posed great danger to their health and environment; 22 percent found it “somewhat serious”; nine percent, “a little serious”; and 19 percent, “hardly serious.”

While growing concern for water pollution was noted among residents in urban areas, with 58 percent finding it unacceptable that economic progress should mean environmental destruction, some 48 percent said they were not aware of any laws enacted to help prevent pollution.

Among the environmental policies cited in the survey were the Clean Water Act and the Solid Waste Management Act.

Out of the 1,200 respondents, 26 percent said they were familiar with the Clean Water Act; 27 percent were aware of the Solid Waste Management Act while 50 percent admitted not knowing about the laws.