Until recent years, you probably didn’t think much about water. It was always there when you wanted it: for drinking, washing your clothes, or taking a shower. However, in the early summer of 2002, the severe drought in Taiwan changed all that, and water was suddenly on everyone’s mind. Reservoirs throughout the island were depleted to record levels because of the lack of rainfall. Water rationing had to be instituted in much of Taiwan.

Taiwan was by no means alone in its water problems. Today, many countries face a serious water shortage, and the problem will only get worse. The International Water Management Institute (IWMI) predicts that by 2025, severe water shortages will affect 2 to 3 billion people.

Water scarcity is a complex problem involving several factors. Water is a reusable resource. That means the amount of water on the Earth is finite, but it can be used over and over again. Since the amount of water is finite, there are problems with supply when demand increases. It is important to remember that 97 percent of the Earth’s water is in the oceans, and most of the rest is frozen in the polar ice caps. That means less than 1 percent of the world’s water is usable.

Increased demand for water resources comes from two main sources: population growth and industrialization. Industrial use and agricultural irrigation together account for more than 90 percent of human water use. As populations rise, the need for water for food production also increases.

Industry requires large amounts of water. It is estimated that each person needs about 100 liters of water per day for drinking, washing, and cooking, but usage in industrialized countries is typically over 200 liters per person per day, and can be as high as 450.

Climate change can be another cause of water scarcity. While it is hard to prove that global warming has caused specific climate changes, it is certainly one possible factor. Rainfall in Taiwan from January to April in 2002 was only 30 percent of normal, and global warming may be a contributing factor. Pollution is also a problem. When water becomes too polluted to be used safely, there’s less water available.

The water situation worldwide is quickly becoming critical. Urgent measures are needed to avoid a crisis. There are three basic solutions: control population growth, so that the demand for water does not continually increase; conserve water, so that more can be done with existing resources; and develop new water resources.

Conservation can work on a variety of levels. One way to encourage conservation is to increase water prices, which are typically subsidized. Low-flow toilets can reduce water use in the home. Technology can also make irrigation more efficient, requiring less water for the same yield. Industry can also conserve water by using better plumbing and reusing treated wastewater instead of fresh water.

Developing new water sources is difficult because many countries are already using everything available. However, current sources can be made more efficient. For example, silting of reservoirs is a serious problem in Taiwan. Dredging reservoirs can increase their capacity. Desalination of ocean water is another option, though in most areas it is too expensive to be worthwhile. Cleaning up polluted rivers and lakes can also provide more usable water.

Managing water resources will be one of the big environmental issues of the 21st century. There’s only a limited amount, and water is something everyone needs. Taiwan’s water shortage in 2002 has taught us that we cannot take water for granted any more. If we want water in the future, we have to start thinking about how to conserve it now.