future water demands will be met is very important. One approach to this challenge is to work towards setting up a balance in the use and supply of water.
The amount of water used should be less or about the same as the amount of water that is returning to the water source. This approach is an example of sustainability, the use of a natural resource in a manner that it can be renewed or preserved for future generations.
Strategies for sustainable water development that can be used by communities, businesses, or people in their own homes include conservation, redirecting excess water, and desalination.
Conservation involves using less of a resource. By decreasing the amount of water used, the amount of water that is removed from a surface water or groundwater source is reduced. While this does not guarantee that the amount of water flowing back into the sources is more than is being removed, conservation is a first step in managing a limited water supply. Strategies for water conservation around the home include a person turning off the faucet while brushing his teeth, which can save gallons of water each day, and repairing leaking faucets.
A tap that is dripping at a rate of 1 drop every 30 seconds will waste almost a gallon of water every month. Low-flush toilets can save a great deal of water. Putting a brick or container of water in a regular toilet tank will reduce the amount of water used in each flush by reducing the amount of water that the tank can hold.
Bath or shower water can also be reused. This so-called “gray water” is suitable to water lawns or plants. The plumbing from a bathtub is redesigned so it does not drain to the pipe leading from the building into the municipal system. New houses in many parts of the world are being built this way. For now, those in an older home can put pails at the base of the outside drains; collected rainwater is another good source of garden water.
Industry and municipalities are also employing strategies to conserve water. Many industries that use water in their manufacturing processes are cooling and recycling water that would normally be put into the municipal sewer system early during the manufacturing process. Most textile (cloth goods) industries, for example, now use filters to remove large quantities of salt and other materials from water used during the manufacturing process, enabling the reuse of some of the water.
Irrigation systems used in agriculture have been improved to reduce evaporation while watering crops. Municipalities educate the public about water conservation methods and enforce laws designed to promote water conservation, such as requiring low-flush toilets in new construction.
Redirecting excess water
On a larger scale there are steps that can be taken to help replenish the water that moves from the surrounding area to its final underground location (aquifer). During the rainy time of year water is often taken from a river or other surface water source and deliberately stored underground for use during drier times. In southwest Florida this strategy has been successful.
After surface water is treated to remove harmful chemicals and microorganisms it is pumped into an area of the aquifer that is kept separate from the rest of the underground water. This is a safety measure that protects the rest of the underground water in case the added water proves to be contaminated. When needed, this added water can be pumped out and used.
In a similar move water is often taken from surface water sources during the times of year when there is more rain and water levels are higher. Instead of pumping the water underground however, the water is stored above ground in tanks, holding ponds, and other storage areas. Again, the water will be available in times of need.
Another strategy that is proving valuable in areas located near salt water is the removal of minerals such as salt from the water (desalination). There are more than 7,500 desalination plants operating in the world, with some 4,500 in the Middle East alone.
The technique used for desalination can produce water that is near drinking-water quality from sewage water. Although people may not wish to drink this water it is fit for use on crops, which saves water from surface and underground freshwater supplies.
The technique of desalination uses a material that contains many tiny holes to filter the water. Water molecules are small enough to pass through the filter but molecules of sodium (salt) are too big, and so pile up on one side of the filter. Powerful pumps force the water through the holes of the filter, producing water that is almost free from salt.
Additional strategies for water supply sustainability
irrigation is to spray the water onto the fields. However this method wastes water as leakage and evaporation remove almost half of the water before it reaches the ground. The wasting of freshwater in irrigation can be reduced by burying the water pipe at the roots of the plants. As water oozes out of the pipe, the liquid can be soaked up by the roots.
If spraying is necessary, directing the sprayer closer to the crop or dripping water onto the crop can reduce water loss due to the change of liquid water-to-water vapor (evaporation). If channels of water (a passage for water dug into the earth) are used in a field, covering the channels from sunlight also reduces evaporation.
In Chile, a project has adapted a centuries-old technique that uses the plentiful clouds of water vapor (fog) in the mountainous villages to supply water for drinking and irrigation. The villagers string up mesh nets between two posts.
As the clouds pass through what look like big volleyball nets, water forms beads on the mesh. The droplets drain down to gutters that empty into a storage tank. This simple system naturally produces up to 4,000 gallons (15,141 liters) of water per day, enough water to fill over 100 bathtubs.
Some public water suppliers reduce the use of water and help pay for keeping surface and groundwater supplies clean and plentiful by charging extra fees for increased water use. This encourages industry and people in their homes to conserve water. Many communities also work to educate citizens about the importance of a sustainable water supply.