Water crisis
The water crisis is the status of the worlds water resources relative to human demand as of the 1970s and to the current time. The term "water crisis" has been applied to the worldwide water situation by the United Nations and other world organizations. The major aspects of the water crisis are overall scarcity of usable water and water pollution.
The Earth has a finite supply of fresh water, stored in aquifers, surface waters and the atmosphere. Sometimes oceans are mistaken for available water, but the amount of energy needed to convert saline water to potable water is prohibitive today, explaining why only a very small fraction of the world's water supply derives from desalination.
There are several principal manifestations of the water crisis.
- Inadequate access to safe drinking water for about 1.1 billion people
- Groundwater overdrafting leading to diminished agricultural yields
- Overuse and pollution of water resources harming biodiversity
- Regional conflicts over scarce water resources sometimes resulting in warfare
Waterborne diseases and the absence of sanitary domestic water is the leading cause of death worldwide and may account for up to 80 percent of human sickness.
Historically the manifestations of the water crisis have been less pronounced, but 20th century levels of human overpopulation have revealed the limited quantity of fresh water. Drought dramatizes the underlying tenuous balance of safe water supply, but it is the imprudent actions of humans that have rendered the human population vulnerable to the devastation of major droughts.

# Health impacts of the water crisis
Not only are there 1.1 billion without adequate drinking water, but the United Nations acknowledges 2.6 billion people are without adequate water for sanitation (e.g. wastewater disposal). The issues are coupled, since, without water for sewage disposal, cross-contamination of drinking water by untreated sewage is the chief adverse outcome of inadequate safe water supply. Consequently disease and significant deaths arise from people using contaminated water supplies; these effects are particularly pronounced for children in underdeveloped countries, where 3900 children per day die of diarrhea alone.
While these deaths are generally considered preventable, the situation is considerably more complex, since the Earth is beyond its carrying capacity with respect to available fresh water. Often technology is advanced as a panacea, but the costs of technology presently exclude a number of countries from availing themselves of these solutions. If lesser developed countries acquire more wealth, partial mitigation will occur, but sustainable solutions must involve each region in balancing population to water resource and in managing water resources more optimally. In any case the finite nature of the water resource must be acknowledged if the world is to achieve a better balance.

# Damage to biodiversity
Vegetation and wildlife are fundamentally dependent upon adequate freshwater resources. Marshes, bogs and riparian zones are more obviously dependent upon sustainable water supply, but forests and other upland ecosystems are equally at risk of significant productivity changes as water availability is diminished. In the case of wetlands, considerable area has been simply taken from wildlife use to feed and house the expanding human population. But other areas have suffered reduced productivity from gradual diminishing of freshwater inflow, as upstream sources are diverted for human use. In seven states of the U.S. over 80 percent of all historic wetlands were filled by the 1980s, when Congress acted to create a no net loss of wetlands.
In Europe extensive loss of wetlands has also occurred with resulting loss of biodiversity. For example many bogs in Scotland have been drained or developed through human population expansion. One example is the Portlethen Moss in Aberdeenshire, that has been over half lost, and a number of species which inhabited this moss are no longer present such as the Great Crested Newt.
On Madagascars central highland plateau, a massive transformation occurred that eliminated virtually all the heavily forested vegetation in the period 1970 to 2000. The slash and burn agriculture eliminated about ten percent of the total countrys native biomass and converted it to a barren wasteland. These effects were from overpopulation and the necessity to feed poor indigenous peoples, but the adverse effects included widspread gully erosion that in turn produced heavily silted rivers that run red decades after the deforestation. This eliminated a large amount of usable fresh water and also destroyed much of the riverine ecosystems of several large west-flowing rivers. Several fish species have been driven to the edge of extinction and some coral reef formations in the Indian Ocean are effectively lost.

# Regional conflicts
There are approximately 260 different river systems worldwide, where conflicts exist crossing national boundaries. While Helsinki Rules help to interpret intrinsic water rights among countries, there are some conflicts so bitter or so related to basic survival that strife and even warfare are inevitable. In many cases water use disputes are merely an added dimension to underlying border tensions founded on other bases.
The Tigris-Euphrates River System is one example where differing national interests and withdrawal rights have been in conflict. The countries of Iran, Iraq and Syria each present valid claims of certain water use, but the total demands on the riverine system surpass the physical constraints of water availability. As early as 1974 Iraq massed troops on the Syrian border and threatened to destroy Syrias al-Thawra dam on the Euphrates.
In 1992 Hungary and Czechoslovakia took a dispute over Danube River water diversions and dam construction to the International Court of Justice. This case represents a minority of disputes where logic and jurisprudence may be the path of dispute resolution. Other conflicts involving North and South Korea, Israel and Palestine, Egypt and Ethiopia, may prove more difficult tests of negotiation.

# Overview of regions suffering crisis impacts
There are many other countries of the world that are severely impacted with regard to human health and inadequate drinking water. The following is a partial list of some of the countries with significant populations (numerical population of affected population listed) whose only consumption is of contaminated water:
- Sudan  12.3 million
- Iran   5.6 million
- Venezuela 5.0 million
- Syria   3.8 million
- Zimbabwe 2.7 million
- Tunisia  2.1 million
- Cuba   1.2 million
According to the California Department of Water Resources, if more supplies arent found by 2020, region will face a shortfall nearly as great as the amount consumed today. Los Angeles is a coastal desert able to support at most 1 million people on its own water; the Los Angeles basin now is the core of a megacity that spans 220 miles (350 km) from Santa Barbara to the Mexican border. The regions population is expected to reach 22 million by 2020. The population of California continues to grow by more than a half million a year and is expected to reach 48 million in 2030. But water shortage is likely to surface well before then.
Water deficits, which are already spurring heavy grain imports in numerous smaller countries, may soon do the same in larger countries, such as China or India. The water tables are falling in scores of countries (including Northern China, the US, and India) due to widespread overpumping using powerful diesel and electric pumps. Other countries affected include Pakistan, Iran, and Mexico. This will eventually lead to water scarcity and cutbacks in grain harvest. Even with the overpumping of its aquifers, China is developing a grain deficit. When this happens, it will almost certainly drive grain prices upward. Most of the 3 billion people projected to be added worldwide by mid-century will be born in countries already experiencing water shortages. Unless population growth can be slowed quickly by investing heavily in female literacy and family planning services, there may not be a humane solution to the emerging world water shortage.
After China and India, there is a second tier of smaller countries with large water deficits  Algeria, Egypt, Iran, Mexico, and Pakistan. Four of these already import a large share of their grain. Only Pakistan remains self-sufficient. But with a population expanding by 4 million a year, it will also likely soon turn to the world market for grain.
According to a UN climate report, the Himalayan glaciers that are the sources of Asia's biggest rivers - Ganges, Indus, Brahmaputra, Yangtze, Mekong, Salween and Yellow - could disappear by 2035 as temperatures rise. Approximately 2.4 billion people live in the drainage basin of the Himalayan rivers. India, China, Pakistan, Bangladesh, Nepal and Myanmar could experience floods followed by droughts in coming decades. In India alone, the Ganges provides water for drinking and farming for more than 500 million people.

# Outlook
Year 2025 forecasts state that two thirds of the world population will be without safe drinking water and basic sanitation services. Construction of wastewater treatment plants and reduction of groundwater overdrafting appear to be obvious solutions to the worldwide problem; however, a deeper look reveals more fundamental issues in play. Wastewater treatment is highly capital intensive, restricting access to this technology in some regions; furthermore the rapid increase in population of many countries makes this a race that is difficult to win. As if those factors are not daunting enough, one must consider the enormous costs and skill sets involved to maintain wastewater treatment plants even if they are successfully developed.
Reduction in groundwater overdrafting is usually politically very unpopular and has major economic impacts to farmers; moreover, this strategy will necessarily reduce crop output, which is something the world can ill afford, given the population level at present.
At more realistic levels, developing countries can strive to achieve primary wastewater treatment or secure septic systems, and carefully analyse wastewater outfall design to miminise impacts to drinking water and to ecosystems. Developed countries can not only share technology better, including cost-effective wastewater and water treatment systems but also in hydrological transport modeling. At the individual level, people in developed countries can look inward and reduce overconsumption, which further strains worldwide water consumption. Both developed and developing countries can increase protection of ecosytems, especially wetlands and riparian zones. These measures will not only conserve biota, but also render more effective the natural water cycle flushing and transport that make water systems more healthy for humans.

# Desalination
As new technological innovations continue to reduce the capital cost of desalination, more countries are building desalination plants as a small element in addressing their water crises , .
- Israel desalinizes water for a cost of 53 cents per cubic meter .
- Singapore desalinizes water for 49 cents per cubic meter .
- China and India, the world's two most populous countries, are turning to desalination to provide a small part of their water needs , .
- In 2007 Pakistan announced plans to use desalination .
- Australia uses desalination .
- In 2007 Bermuda signed a contract to purchase a desalination plant .
- Desalination allows Dubai to have year round indoor skiing in the middle of the desert .
- In the United States, California, Arizona, Texas, and Florida use desalination for a very small part of their water supply , , .
Nuclear power is one way to provide the energy for desalination. , , , .
Cheaper alternatives to million-dollar desalianation projects are water filters, such as reverse osmosis water processors and vapaires. These are often more viable when shortage of funds is an obstacle.