BIG SQUEEZE: On the world's freshwater resources looms as populations mushroom and incomes rise.
Cary Wolinsky

Key Concepts

• Global freshwater resources are threatened by rising demands from many quarters. Growing populations need ever more water for drinking, hygiene, sanitation, food production and industry. Climate change, meanwhile, is expected to contribute to droughts.
• Policymakers need to figure out how to supply water without degrading the natural ecosystems that provide it.
• Existing low-tech approaches can help prevent scarcity, as can ways to boost supplies, such as improved methods to desalinate water.
• But governments at all levels need to start setting policies and making investments in infrastructure for water conservation now.

A friend of mine lives in a middle-class neighborhood of New Delhi, one of the richest cities in India. Although the area gets a fair amount of rain every year, he wakes in the morning to the blare of a megaphone announcing that freshwater will be available only for the next hour. He rushes to fill the bathtub and other receptacles to last the day. New Delhi’s endemic shortfalls occur largely because water managers decided some years back to divert large amounts from upstream rivers and reservoirs to irrigate crops.

My son, who lives in arid Phoenix, arises to the low, schussing sounds of sprinklers watering verdant suburban lawns and golf courses. Although Phoenix sits amid the Sonoran Desert, he enjoys a virtually unlimited water supply. Politicians there have allowed irrigation water to be shifted away from farming operations to cities and suburbs, while permitting recycled wastewater to be employed for landscaping and other nonpotable applications.

As in New Delhi and Phoenix, policymakers worldwide wield great power over how water resources are managed. Wise use of such power will become increasingly important as the years go by because the world’s demand for freshwater is currently overtaking its ready supply in many places, and this situation shows no sign of abating. That the problem is well-known makes it no less disturbing: today one out of six people, more than a billion, suffer inadequate access to safe freshwater. By 2025, according to data released by the United Nations, the freshwater resources of more than half the countries across the globe will undergo either stress—for example, when people increasingly demand more water than is available or safe for use—or outright shortages. By midcentury as much as three quarters of the earth’s population could face scarcities of freshwater.

Scientists expect water scarcity to become more common in large part because the world’s population is rising and many people are getting richer (thus expanding demand) and because global climate change is exacerbating aridity and reducing supply in many regions. What is more, many water sources are threatened by faulty waste disposal, releases of industrial pollutants, fertilizer runoff and coastal influxes of saltwater into aquifers as groundwater is depleted. Because lack of access to water can lead to starvation, disease, political instability and even armed conflict, failure to take action can have broad and grave consequences.

Fortunately, to a great extent, the technologies and policy tools required to conserve existing freshwater and to secure more of it are known; I will discuss several that seem particularly effective. What is needed now is action. Governments and authorities at every level have to formulate and execute concrete plans for implementing the political, economic and technological measures that can ensure water security now and in the coming decades.

Sources of Shortages
Solving the world’s water problems requires, as a start, an understanding of how much freshwater each person requires, along with knowledge of the factors that impede supply and increase demand in different parts of the world. Malin Falkenmark of the Stockholm International Water Institute and other experts estimate that, on average, each person on the earth needs a minimum of 1,000 cubic meters (m³) of water per year—equivalent to two fifths of the volume of an Olympic-size swimming pool—for drinking, hygiene and growing food for sustenance. Whether people get enough depends greatly on where they live, because the distribution of global water resources varies widely.

Providing adequate water is especially challenging in drier, underdeveloped and developing nations with large populations, because demand in those areas is high and supply is low. Rivers such as the Nile, the Jordan, the Yangtze and the Ganges are not only overtaxed, they also now regularly peter out for long periods during the year. And the levels of the underground aquifers below New Delhi, Beijing and many other burgeoning urban areas are falling.