Human Water Use

Because people everywhere need freshwater for drinking, agriculture, transportation, industry, and hydroelectric power, the relative scarcity of freshwater on the planet is becoming an increasing serious problem. Currently, for example, the use of freshwater worldwide is growing at twice the rate of population growth. Each day, the United States uses 1,500 gallons of water per capita, and its yearly per capita water withdrawal amounts to 500,000 gallons. If people continue to use freshwater at such high rates, there will be little water available for future generations.

Domestic Water Use in the United States

A major sector of US water use is domestic. Toilets represent 38% of domestic water use, baths represent 31%, laundry machines and dishwashers represent 20%, drinking and cooking represent 6%, and other uses such as brushing teeth represent 5%. Water heaters are the second largest energy users in most homes, as only space heating and cooling systems use more. 25% of an average home's total electricity heats water for laundry, cleaning, and bathing.

People can conserve domestically used freshwater easily by making small changes in their lifestyles. For example, they can take shorter showers, use low-flush toilets, fix leaks, buy plants that require less water, or water their plants in the morning or evening, when the sun is weaker and less of the water will evaporate. Simple adjustments such as these can make a huge difference if made by a large number of people.

Alternative Sources of Water

If humans continue to use freshwater at the current rates, alternative sources may soon become necessary. One possible method of obtaining more freshwater is the desalinization of saltwater from the ocean. This process can be accomplished using distillation or reverse osmosis, but it is very expensive and requires large amounts of energy. Distillation involves heating salt water until it evaporates and condenses as fresh water, leaving behind salt in its solid form. During reverse osmosis, salt water is pumped at high pressure through a membrane that allows water molecules to pass through, but not dissolved salts. Currently, about 11,100 desalinization plants exist, but even so, they provide less than 0.15% of the world's freshwater.

Some countries have instituted massive water projects in order to prevent present and future water shortages. Many of these projects include dams that collect freshwater, man-made lakes that store it, and canals or pipelines that transport it to the country's citizens. Such attempts have proved effective at providing hydroelectric power and water for agriculture, but a number of significant drawbacks have emerged. These drawbacks include salt and silt build-up, high cost, a negative environmental impact, leakage and evaporation, and controversy over water rights.

Another method that has been employed in the search for alternative sources of freshwater is the "seeding" of clouds. During this process, scientists use dry ice, potassium iodide, and other chemicals to bring water to needed areas. The chemicals produce rain where it is needed, but this only results in water loss elsewhere, and the salts also represent a source of pollution. The most feasible method of obtaining freshwater is actually the simplest: reuse and recycling. Filtering and chemical treatment of polluted water can purify it enough for use in homes, agriculture, and landscaping. This method is less expensive and more effective that the previous approaches listed.