Water resources

Water resources are sources of water that is actually usable for drinking, farming and industry. While 70% of the Earth's surface is covered with salt water, the supply of fresh, clean water is so limited as to constitute a serious problem in many parts of the world. It has been predicted that global scarcity of water resources will occur many decades before the much-heralded depletion of fossil fuel resources.

Table of contents 1 The problem 2 The result 2.1 Solutions 3 Conservation 4 Development 5 Importing water

The problem

Human populations in some areas (e.g. southern California, Israel, and Florida) are growing a 1 to 3% per year, while fresh water supplies are remaining constant or shrinking.

Most new available water supplies 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 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.

The result

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. (They weren't kidding when they said 'There isn't room for both of us...')

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 Lake, and drained it to dust, also over bitter protests.

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. In areas where law is less respected than in the U.S., we can expect either violence, or poverty.

Solutions

Conservation

One part of the solution is conservation. People will pay almost any amount for drinking water. However, far less water can sometimes be used for irrigation, wash water and industrial water.

World-wide, crops irrigated by ditches use 70% or more of available water. Changing to dry-land crops and sprinkler or drip irrigation can reduce agricultural water use by 60 to 90%.

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. Almost all 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 swamps in river deltas, 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. This "reclaimed water" is used for irrigation, recharging aquifers, or discharge into lakes.

Development

Desalination has long been used on ships, submarines and islands, where cost is no object.

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.

Importing water

Water has such a low value per pound 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 pounds of water to grow one pound of grain. Thus, each ton of imported grain saves 1000 tons of domestic water. This method is used by Israel, which imports most grain.