(Redirected from Drinking water
Water resources are sources of water that are useful to human beings for drinking, recreation, irrigation, livestock production, industry, etc. Even though 70% of the Earth's surface is covered with water, a majority of it is salt water. Only 3% of water on the Earth is fresh water, and over two thirds of this is frozen in glaciers and polar ice caps . The supply of fresh water is so limited in many parts of the world that the shortage constitutes a serious problem for the human inhabitants. It has been predicted that global scarcity of water resources will occur many decades before the much-heralded depletion of fossil fuel resources. Water scarcity is but one side of the problem; water quality is the other, in as much as a resource can also be lost through its degradation.
Human populations in some areas (e.g. southern California, Israel, and Florida) are growing from 1 to 3% per year, while fresh water supplies are remaining constant or shrinking.
Most new available resources are contaminated with industrial waste, sewage or salt. Aquifers are already being rapidly used, so even ground water is no longer a practical solution.
Most water purification plants use large amounts of oil or other fuel. Nuclear purification plants are politically unpopular. Solar purification plants require too much land and are very expensive.
In poor and arid countries, such as much of the developing world, water scarcity is truly a massive humanitarian problem. Not only water scarcity but also low water quality are believed responsible for a large number - perhaps the majority - of deaths in the developing world.
An increasing number of wars and civil disputes are occurring over water rights.
In the U.S.'s western region, this is not news. Water wars in the U.S. date from the western expansion of the 1820s, even though most of them were fought by private landowners. The historic cowboy range wars were over water rights. Land-theft and rustling were usually attempts to get compensation for or access to water. Mark Twain summed up the conflict by saying, "Whiskey is for drinking. Water is for fighting over."
Civil disputes in the U.S. also have a long history, especially in California, after the population expansion of the 1850s. Both San Francisco, California and Los Angeles, California engaged in lengthy negotiations, property acquisition, and litigation to secure water rights. San Francisco flooded a beautiful glacial valley, Tehatchapi, over the bitter protests of conservationists led by the Sierra Club. Los Angeles purchased Mono Valley, and drained it to dust, also over bitter protests. The California Water Wars resulted from such incidents.
In the Middle East, many of the wars, notably the Six-Day War, have been disputes over water. These are expected to escalate as industry and population increase in the region.
One part of the solution is conservation. People will pay almost any amount for drinking water. (the retail price of bottled water in many cases is greater than that of gasoline in the same area.) However, far more water than may be necessary is presently used for irrigation, wash water and industrial water. With proper resource management, and recycling/reclamation, the wasteful use of water may be greatly decreased.
World-wide, crops irrigated by ditches use 70% or more of available water. Changing to dry-land crops can reduce water use, but with a corresponding drop in production, while switching to sprinkler or drip irrigation may or may not conserve water. In some cases switching to more efficient technologies means higher yields, but without any real decrease in the consumption of water. Good management is also essential to achieve conservation, since these systems can be just as wasteful if not properly managed.
About 15% of water use is industrial. Much industrial water is used for cleaning or cooling. Often the water can be settled, filtered and recycled. This reduces pollution of surface water while reducing use. In some cases, it is profitable for water providing authorities to share the costs of pollution control equipment for industries.
Many authorities say that the way to stop these abuses is simply to charge users the true costs of the water they use. Some areas subsidize farm and industrial uses of water by over-charging residential uses.
In cities, the largest waste of water is as run off during rainy seasons. Most roofs and storm sewers could preserve the water for use. In heavily urban southern California, some runoff is diverted to man-made and natural wetlands, to recharge aquifers and keep ocean water out of city wells.
Some areas of California and Israel use greywater systems, in which household wash water is recycled for irrigation and sewage processing.
A number of cities and water districts in California recycle sewage to standards that would make it usable for drinking or washing water. Though some of this "reclaimed water" is used for irrigation, recharging aquifers, or is discharged into reservoir lakes, some is discharged directly into the ocean.
Desalination has long been used on ships, submarines and islands, where there is no alternative. It has also been used to supply water to the US military base at Guantanamo Bay, Cuba and in Saudi Arabia where fuel is inexpensive and water is scarce. History of water supply at Guantanamo Bay: .
Desalination of brackish water is already commonplace in the U.S., where it is used to meet treaty obligations for river water entering Mexico.
Desalination of ocean water is common in the Middle East, where a number of countries use oil-fired stills to provide city drinking water.
The price of desalination is rapidly declining. A modern, large, efficient plant is within 20% of the cost of developing a new, local source of fresh water. Desalination stills now control pressure, temperature and brine concentrations to optimize the water extraction expense. Other methods of desalination include reverse osmosis and pressure barrier osmosis. Nuclear-powered desalination could be very economical on a large scale.
Water has such a low value per unit weight that it is not usually profitable to import it.
The most effective way to "import" water is in the form of virtual water; that is, to import products that require large amounts of water to produce. A simple example is grain. It usually takes 1000 tons of water to grow one ton of grain. Thus, each ton of imported grain saves 1000 tons of domestic water. This method is used by Israel, which imports most grain.
Importing Water to the US from Canada
The situation between Canada and the US illustrates some of the complexities of importing water.
Canada has 20% of the world's fresh water and the US has a great need for additional fresh water supplies. The two nations share bodies of water like the Great Lakes so water could be easily transferred from Canada to the US. Although the US would seem to be a natural market for its water, Canada refuses to export any fresh water to the US, except as bottled water.
Under the terms of the North American Free Trade Agreement (NAFTA), for any commodity that is normally traded between Canada, Mexico and the US, all the nations must be treated the same as the nation that produces the commodity. If Canada were to start bulk water exports to the US, it would lose control of the exports and would be unable to limit American purchases of additional supplies. In effect, Canadians would end up having to compete with the wealthier Americans for access to their own fresh water supply. The only way to avoid this is to stop any attempt to export fresh water in bulk. Even tanker trucks of fresh water are not allowed to cross the Canadian border.
Although Canada has 20% of the world's fresh water, it only receives 7% of the precipitation. Most of Canada consists of rock (the Canadian Shield) or permafrost. Water cannot sink into these impermeable materials but sits on top. The water collects in every hollow to form Canada's innumerable lakes and rivers. Canada's northern latitude means that little water is lost to evaporation before each reaches the sea and this accounts for Canada's vast supply of fresh water. Canadians are afraid that, if allowed, Americans would “mine” Canada's fresh water by taking more than is replaced each year.
The waters shared by the two nations are controlled by the Boundary Waters Treaty of 1909. This treaty prevents the US from, say, just pumping all the water that it wants out of the Great Lakes.
Water trade in other countries
Hong Kong imports more than 70% of water from Guangdong, China, through pipes connected to the Dongjiang River. Macao also imports water from Guangdong, from Xijiang River. Singapore imports water from Johore, Malaysia.