Special Science Issue Examines Access to Global Freshwater Resources

The latest edition of Science examines freshwater resources

Water, water, everywhere—but not enough to drink?

There is more water in the world than we use every year—yet still around one-fifth of the world’s population does not have access to safe water, and over one-third faces unacceptable sanitary conditions. More than 1.5 million children die each year from diarrheal diseases often caused by consuming water from contaminated sources.

Contributors to the special section in the 25 August 2006 issue of the journal Science highlight some of the world’s contemporary scientific and engineering projects dedicated to obtaining and maintaining freshwater resources. The special section incorporates articles from around the world including a related editorial and a special news package.

The Threat from Micropollutants

We know a fair amount about nutrients and other macropollutants contaminating our freshwater sources, but we are only beginning to understand the harmful effects of so-called micropollutants, say René Schwarzenbach and colleagues in a Review.

These contaminants are synthetic and natural substances that may be present in water at very low concentrations, including heavy metals, organic pollutants such as DDT, or biological products such as hormones and drugs. Micropollutants’ long-term effects on aquatic life and human health are largely unknown at this point, but the authors say they could amount to a problem of similar magnitude as that of water-borne pathogens, which cause more than 2 million deaths annually.

Schwarzenbach and coauthors look at the scientific challenges in addressing water quality problems caused by micropollutants: how to assess the pollutants’ impact, how to treat polluted water, and how to dispose of the micropollutants in the first place.

The Dark Side of Water Development Projects

Dams and other water development projects have opened many possibilities in rural areas, particularly in Africa, but they also come with a terrible burden of disease, says Alan Fenwick in a Perspective.

Fenwick notes that water projects have changed the face of Africa, making land available for agriculture, providing electric power, encouraging settlements near water bodies, and bringing prosperity to poor people. But, the new or modified water bodies also provide ideal conditions for the spread of serious diseases such as cholera, schistosomiasis (blood flukes), malaria, roundworm and hookworm.

Fenwick says that many of these diseases could be controlled effectively by 2015, which is the target for reaching the United Nations’ Millennium Development Goals. Thanks to better advocacy, donated drugs from several pharmaceutical companies and a reduction in the price of the drug praziquantel, he says that the death rate from diseases may be dropping for good.

Going With the Flow

The supply of renewable freshwater resources should be considered in terms of how freshwater is cycled, not just according to how much exists, explain Taikan Oki and Shinjiro Kanae in a Review. Only a fraction of that water is flowing through available reservoirs at any given time or place. Thus, while freshwater is so abundant that it’s taken for granted in developed countries, many people still live in water-stressed conditions in other parts of the world.

Israel’s Evolving Water Strategy

Israel has embarked on an ambitious water management effort over the last 60 years, which has seen significant successes and still faces some tricky problems, according to Alon Tal in a Perspective. Tal describes the various components of Israel’s system, such as the National Water Carrier that transports water from Lake Kinneret in the north to the arid southlands.

Although this project has dramatically expanded cultivated land and harvests in the country’s semiarid regions, it has also exacerbated salinity problems and raised cloudiness levels in the water. Israel also collects rainwater, recycles its wastewater—73 percent of municipal sewage in Israel is treated, as opposed to 2.5 percent in the United States, according to the authors—desalinizes seawater, and encourages water conservation.

Freshening Up the Seas

The freshwater content of the Nordic Seas and Atlantic Subpolar Basins was on the rise between 1955 and 1995. Where did it come from? Bruce J. Peterson and colleagues found that it seems to be coming from increasing river discharge, net precipitation, sea ice melt and glacier melt in these high latitudes.

When researchers compared the available hydrologic data from 1955-1995 to that from 1936-1955, they saw a marked increase in freshwater in the saltwater in the later era. The amount of extra freshwater in the ocean is about the same as that created by the freshwater factors measured, so the researchers concluded that the high-latitude contributions are responsible for the added fresh water.

Only the future will tell if the melting of the Arctic glaciers and Greenland Ice Sheet will begin to play a larger role in contributing freshwater to the oceans, but rising temperature could “amplify that contribution in potentially dramatic ways,” according to the authors.

Evelyn Brown and Kathy Wren

24 August 2006