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Compendium on methods and tools to evaluate impacts of, and vulnerability and adaptation to, climate change


CROPWAT is a DOS or Windows based decision support system designed as a tool to help agro-meteorologists, agronomists, and irrigation engineers carry out standard calculations for evapotranspiration and crop water use studies, particularly the design and management of irrigation schemes. It allows the development of recommendations for improved irrigation practices, the planning of irrigation schedules under varying water supply conditions, and the assessment of production under rainfed conditions or deficit irrigation.

Appropriate Use As a tool for testing the efficiency of different irrigation strategies (e.g., irrigation scheduling, improved irrigation efficiency) under climate change. Does not have the capacity of simulating the direct effects of rising atmospheric carbon dioxide concentrations on crop water use.
Scope All locations; agricultural sector; site-specific.
Key Output Reference evapotranspiration, crop water requirements, and crop irrigation requirements.
Key Input Climatic and crop data (CLIMWAT database, included with the program) for calculations of crop water requirements and irrigation requirements. The development of irrigation schedules and the valuation of rainfed and irrigation practices are based on a daily soil-water balance using various options for water supply and irrigation management conditions.
Ease of Use Relatively easy to use for qualified experts with appropriate background.
Training Required Intended for use by agricultural professionals because it requires background and training in agricultural modeling. Using the manual, an expert can learn how to use this tool within 1-2 days.
Training Available No formal training currently offered beyond the training manual.
Computer Requirements IBM-compatible PC 486 with 4k of RAM and 80MB supporting DOS or Windows. CROPWAT version 5.7, issued in 1992, is written in BASIC and runs in the DOS environment. The program is available in English, French and Spanish. The English version of CROPWAT 5.7 has since been replaced by CROPWAT version 7.0. CROPWAT for Windows contains a CROPWAT version in Visual Basic to operate in the Windows environment.
Documentation CROPWAT for Windows and its manual are available in Acrobat format and can be downloaded from

The CROPWAT database contains data for six continental regions and 144 countries. It has been used to develop irrigation schedules under various management conditions to evaluate rainfed production and drought effects and efficiency of irrigation practices.

Contacts for Framework, Documentation, Technical Assistance

Martin Smith

Senior Irrigation Management Officer, Water Resources, Development, and Management Service, FAO, Viale delle Terme di Caracalla, 00100 Rome, Italy; Tel: 39.06.57053818; Fax: 39.06.57056275; e-mail:

Cost No cost to obtain model documentation or software.

Doria, R., C.A. Madramootoo and B.B. Mehdi. 2006. Estimation of Future Crop Water Requirements for 2020 and 2050, Using Cropwat. EIC Climate Change Technology, 2006 IEEE pp 1-6.

FAO Irrigation and Drainage Paper No. 46. Food and Agriculture Organization, Rome.

FAO. 1992. CROPWAT — A Computer Program for Irrigation Planning and Management.