Water shortages on planet Earth? It seems impossible. Images of our planet from outer space show vast oceans, lakes as big as small countries, and wide rivers flowing with incredible volume. How can there not be enough water? Earth has enormous water resources, approximately 1.35 billion cu km (about 326 million cu mi) of it, enough to submerge the United States (including Alaska and Hawaii) under 147 km (92 mi) of water. But more than 97 percent of it is salt water, lethal to crops and unfit for human consumption. Earth’s freshwater resources are much smaller, about 38 million cu km (about 9 million cu mi), and in some regions they are coming under stress. The world is facing the prospect of water shortages caused by population growth, uneven supplies of water, pollution, and other factors. The
United Nations (UN) predicts that water shortages could retard the economic growth of some countries and lead to food shortages and, possibly, to international conflicts as countries compete for limited water resources. The wars of the next century will be over water not oil.
PollutionPollution also affects the water supply, reducing the available water by making it toxic or otherwise unfit for human use.
Nitrates from farm fertilizers as well as industrial chemicals can sink into groundwater or flow into streams, where they pose risks to both health and the environment. High levels of nitrates can also damage the environment by stimulating
algae growth. The
algae reduce the amount of oxygen in the water (a process known as eutrophication), killing other organisms. Animal and human wastes represent another source of water pollution. This type of water pollution is an issue throughout the world, but is worst in the less industrialized nations of Africa, Asia, and Central America. At least 20 percent of the world’s population has no access to drinking water that is free from pollutants or disease-causing microbes. This means that, at any one time, approximately half of the people in the developing world suffer from conditions such as diarrhea (the causes of which are often transmitted through water).
Climate ChangeClimate changes caused by global warming could also affect water resources.
Global warming is caused by burning
fossil fuels, such as
oil and
coal, and by some agricultural and industrial processes. These activities contribute to rising amounts of greenhouse gases (gases that trap the sun’s heat) in the atmosphere. Scientists disagree over the extent to which global warming might alter the Earth’s climate and how quickly it might do so. Nevertheless, most experts agree that elevated global temperatures could change the world’s rainfall patterns. This change could create or worsen water stress in some regions while perhaps alleviating it in others.
Clean It UpMost experts agree that both humans and the environment benefit when steps are taken to combat
water pollution. Many steps can be taken in this area, from laws that regulate polluters and set standards for clean water to education programs that teach people how to avoid polluting local rivers, lakes, and aquifers. International efforts to control water pollution face many challenges. Countries do not always agree on what needs to be done or who should pay for it. Nevertheless, the world has agreed on some basic principles. Sewage treatment plants, for example, can cost millions of dollars. Nevertheless, the benefits—a healthier environment and population—are worth the price.
Is Desalination the Answer to Water Shortages?
If the world needs large quantities of water, one obvious place to get it is from the oceans. It seems so reasonable: When Earth’s growing population runs short of fresh water, water will have to be taken from the sea and desalinated (have the salt taken out). Several different methods can be used to desalinate seawater. Flash evaporation turns the water to steam, leaving the salt behind. The steam is then condensed into fresh water. This is the most widely used method of desalination. The main drawback to desalinated water is that it uses large amounts of costly energy. Nevertheless, current technology is economical for desalinating brackish well water, water that is salty, but less so than seawater
Looking Forward
Despite the fact that the ways people use water have caused shortages and water stress in many regions of the world, humans have not yet crossed the line of no return. There are many practical, cost effective measures that can reduce the strain of water resources. Improved irrigation techniques can reduce water losses and improve crop yields. Investments in sanitation can give more people access to safe water. Water pollution can be reduced. Countries can find new ways to cooperate on water issues. Looking toward 2050 we could balance supply and demand. The question is whether basic human needs will be met, and the environment will be healthy. The conservation technologies are there. It’s a matter of whether we decide to mobilize and get the job done.
