World Water and Climate Atlas

International Water Management Institute

The IWMI World Water and Climate Atlasprovides rapid access to the global climate dataneeded to understand and solve many of theworld’s water scarcity and food security problems.

Using the Atlas, irrigation and agriculturalplanners can answer questions such as:

· Where can rainfed agriculture beexpanded? Where can supplementalirrigation increase crop yields? Where isirrigation essential for viable agriculture?

· How much irrigation do crops need inrelation to what the climate provides?

· What areas are suitable for specific crops interms of maximum and minimumtemperatures and other climatic variables?

· Where should an irrigation scheme besited? What is the potential for waterharvesting?

· How much water is entering a river basinsystem through rainfall, and how much isleaving through evaporation and planttranspiration?

Direct access to water and climate data improves agricultural planning

þ A view of annual precipitation and reference evapotranspiration rates.

Creation of the World Water and Climate Atlas was made possible by support from the Government of Japan(Official Development Assistance) and the United States Agency for International Development (USAID)

The IWMI Digital World Water and Climate Atlas brings together water, climate and agricultural datafrom sources around the world and presents it in an easy to use software tool. Planners can accessthis key water and climate data instantly, import their own data, or export data from the Atlas foruse in other applications.

Sri Lanka LocalizedGridding Study

An example of the Atlas’s localizationcapability. This map of average totalprecipitation per year for Sri Lanka shows howthe detail and precision of global data sets canbe improved by incorporating local data.

Rapid access to key climate variables for agriculture and waterresource management. The core of the Atlas is 30 years’ of datafrom some 30,000 meteorology stations from around theworld—including data that was not previously available in thepublic domain. The IWMI Atlas provides users with monthlyvalues for: total precipitation; amount of precipitationexceeded 75% of the time (P75); average temperature;maximum and minimum temperatures; relative humidity;hours of sunshine; number of frost days; wind speed andPenman-Montieth reference evapotranspiration rates.

High resolution data for regional and national planning. TheAtlas’s 10 minute arc (one-sixth of a degree) resolution —the highest ever offered for a global data set of this kind—makes it a valuable tool for local and national-levelplanning. The largest squares on the Atlas grid are only16 km2 at the equator. These grids can be even furtherrefined by incorporating local data.

Quick and easy data analysis. The Synthesizer software allows users to easily view, manipulate andanalyze data according to their needs. For example, the software can rapidly identify locations thatmatch specific agricultural needs. This function helps match crop varieties with locations that havecertain climatic characteristics. Another function enables the user to create mathematical equationsusing the Atlas grids as variables. A simple example is Tmean – (Trange x .5) = Tmin.

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Using the Atlas to show and manipulate data to calculate referenceevapotranspiration.

Compatible with other data products for a clearer picture ofagricultural potential. Users can combine information onelevation, land cover, soil type, population densityvegetative indices, stream flow, developed water resourcesand other data to enable multi-parameter evaluations.

Crop modeling. Planners can use the Atlas to see wherespecific crops can and cannot be grown and where certainvarieties are most likely to be successful. It also helpsidentify regions which meet climate, soil and altituderequirements.

Annual precipitation and reference evapotranspiration rates. With thisinformation, planners can estimate how much water is available on a monthlybasis and how much water crops need.

Identifying the potential for rainfed agricultureThe water/food security challenge for developing countries is to efficiently manage their waterresources in the face of increasing water scarcity. The Atlas gives food security planners an accurateand easy-to-use overview of their country’s situation.

Rainfed agricultural potential for sub-SaharanAfrica. This map, generated from the Atlas,shows that the potential for rainfed productionis near zero for all of Namibia and Botswana,for much of South Africa, and parts of Somaliaand Kenya.

IWMI estimates that by 2025 cereal production will haveto increase by 38% to meet world food demands. One ofthe most heated debates surrounding world food policy iswhether this additional demand will require largeinvestments in new irrigation systems or whether increasedarea and yields from rainfed agriculture can satisfy asubstantial part of food demand. This issue is becomingincreasing important as the competition between uses andusers of water escalates in many developing countries.

The Atlas helps identify areas where climatic conditionsare favorable for rainfed agriculture. This picture can berefined further with the addition of data on soil type,elevation and land cover.

Increasing the productivity of marginal rainfed agriculture is the key for many countries to radicallyimprove food security and reduce rural poverty—it is poor people who farm the bulk of marginallands. Supplemental irrigation—that delivers water to crops at key growth stages when rains fail—is anaffordable and effective solution. The Atlas helps identify where this approach will substantiallyimprove crop yields. It can also make rapid assessments of the potential for water harvesting in aspecific region or sub-region.

Improving IrrigationPlanning & Management

In the past, assembling the data necessary to plan anirrigation or water-related development project could takemonths. The Atlas can reduce this preparation time to daysor even hours. For planners in developing countries, thisaccess to accurate data, presented in a standardized format,means smoother project design and timely implementation.

The Atlas is also a useful seasonal planning tool forirrigation managers—enabling them to quickly evaluatecrop water requirements.

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Malaria risk mappingThe Atlas is helping IWMI researchers to more accurately identify high-risk malaria areas. Previousrisk mapping studies have used precipitation as the primary indicator of malaria risk. IWMI researchersare developing a picture of seasonal soil moisture content—a more reliable malaria risk indicator—usingthe climate data provided by the Atlas, with data from the Food and Agriculture Organization’s DigitalSoil Map of the World. Based on this information, it is possible to see where and when conditions arefavorable for the breeding of malaria-carrying mosquitoes. IWMI`s research will look further refine thesemaps using satellite remote sensing tools.

Testing New MethodologiesIWMI scientists are developing a simple, single equation method for calculating potentialevapotranspiration anywhere in the world—a technique made possible with the Atlas’ comprehensivedata set. This new method, extending the original Hargreaves approach, only requires data on maximumand minimum temperatures, provides a practical alternative to the Penman-Montieth method insituations where there is minimal or inaccurate climate data.

Some applications using the World Water and Climate Atlas,taken from IWMI’s research program.

Answering the question: “how much irrigation do we really need?”As a first step towards determining the world’s future irrigation requirements, IWMI researchers are usingthe Atlas to calculate the global potential for rainfed agriculture. Previous global studies relied on coarse-resolution climate data. The new IWMI study combines the Atlas’s high resolution data (39 times moreaccurate than the standard generally available 30 minute arc resolution) with a soil water storage capacitymap and a dynamic water and crop model, to estimate potential for rainfed agriculture. The Atlas datasets high resolution allows global scale analysis without losing sight of regional scale implications.

Potential for rainfed agriculture. On a global scale, 46% of the earth’s surface is unsuitable for rainfed agriculture due to climaticconstraints. This leaves approximately 7 billion ha with a potential for rainfed crop production, of which, 4.7 billion ha is classifiedas moderate to highly suitable. Researchers are currently refining this preliminary estimate taking into consideration non-climaterelated factors (e.g. areas not available for conversion to agriculture).

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Potential for rainfed agriculture on a global scale

Data from the Atlas showing annual precipitation and reference evapotranspiration.This same data can be displayed by month.

Download the Atlas from www.iwmi.org The Atlas software and worldwide grids (nine regions,12 months, 10 parameters) can be downloaded from the IWMI website or delivered onCD-ROM. A library of data products compatible with the Atlas is also available on the IWMIwebsite.

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Postal AddressP O Box 2075ColomboSri Lanka

Location127, Sunil MawathaPelawatteBattaramullaSri Lanka

Tel.+94-1 867404

Fax+94-1-866854

E-Mailiwmi@cgiar.org

Websitewww.iwmi.org