Water, water not quite everywhere and not enough of it. And what very little fresh water the world has, it is squandering. That's the message of the Consultative Group on International Agricultural Research (CGIAR) as it looks to the needs of the planet's farms and urban areas in the next century.

Although 70 percent of the planet is covered with water, the kind used for agriculture is becoming scarce. As the world population continues to grow, the need for more food grows with it.

About 150,000 gallons of water is needed to grow one ton of grain, some of which goes into products such as bread and pasta. Some is fed to animals that, in turn, need more drinkable water.

According to CGIAR, water scarcity, not shortage of land, is the main constraint for future agricultural production: "One-quarter of the world's population will suffer severe water scarcity within the next 25 years, even during years of average rainfall."

The group's mission is to promote sustainable agriculture for food security in developing countries. Water usage is one of several closely related problems that plague the world's underdeveloped nations, including poverty, hunger, environmental distress and population increase.

As any child in a geography class knows, there are areas of the world where rainfall is heavy and others that are desert. But it seems that even the most sophisticated planners have not had the tools to match accurately an area's water resources with the proper types of crops to plant or livestock to raise. Crops are grown in all types of areas, from dry to wet, but often inappropriately.

CGIAR is trying to provide computer tools to analyze areas for suitability in crop planning. The tools are being developed by the International Water Management Institute (IWMI) sponsored by CGIAR and are free.

The computer program, known as Synthesizer, and data called The World Water and Climate Digital Atlas can be downloaded from the Internet. If download speed is a prohibitive issue, users can request the data they want, and IWMI will send it on a CD.

IWMI studies water use worldwide. Its mission is to give governments, scientists, farmers and schools the means to study and analyze climate and water availability and usage for any place on Earth at a resolution of 30 seconds of arc, or about half a mile.

Each degree of arc is divided into 60 minutes, each of which contains 60 seconds. There are, of course, 360 degrees in a circle around Earth. At the equator, one second is about .02 miles.

IWMI currently has data for the entire world at a resolution of 2.5 minutes, about three miles, useful for fairly large regions such as river basins but not adequate for much smaller areas.

Based in Sri Lanka, IWMI first produced a high-resolution, 30-second database of the island nation that clearly illustrates the detail of precipitation patterns that can vary greatly within small areas. Since then, IWMI has made a climate atlas of Asia that includes maps of dependable precipitation in conjunction with the rate that plants use water.

Ultimately, IWMI hopes to gather this kind of data and more for countries worldwide. Then, anyone, anywhere could obtain information needed to plan properly the kinds of crops to plant in his or her area, correlated with seasonal rainfall, elevation, soil fertility and many other variables.

Agricultural planners would have an effective means of managing water resources into the next century.

According to CGIAR, too many farms today use intensive, inefficient irrigation. Planting crops that require more water than the climate supplies results in expensive irrigation installations.

Some irrigation efforts, short-term and seasonal, can be economical and effective. But intensive irrigation often draws exorbitant quantities of water from underground, and then the water table drops.

Ismail Serageldin, chairman of CGIAR, says that, while very little data exist on levels of water tables, it is known that they are dropping alarmingly. "New ways must be developed to take advantage of this diminishing resource if humanity is to feed itself in the 21st century," he says.

Given the pressures of population increase and dropping water tables, present-day water usage cannot be sustained. To address this problem, IWMI is facilitating collection of data for analysis at worldwide, regional and local levels. Such data generally is spread among different local and national government agencies.

Information to analyze water table and other important information tied to water usage, rainfall and evaporation rates has never been assembled.

Through better analysis, farmers may find that they should plant a different kind of crop or judge irrigation needs better. In any case, the analysis can help them know what to plant, when to plant it and how to water it.

IWMI hopes to give agricultural agencies, extension centers, farmers and urban planners around the world the tools to plan for demands on water resources over the next few decades and help them to achieve better agricultural yields to help feed a growing world.

You can find IWMI on the Web at www.iwmi.org.

Improving Data

Not too long ago, the most accurate data on rainfall, shown left, had a resolution of just a few pixels for an area the size of Sri Lanka, below. The data set shown in the middle improved accuracy, but IWMI's new data at right give enough resolution to do accurate agricultural planning down to the large farm level.

CAPTION: Improving Data (This chart was not available)