Crop water requirements

Definition / description

The term crop water requirement is defined as the “amount of water required to compensate the evapotranspiration loss from the cropped field” (Allen et al. 1998). The ICID (2000) describes it as the “total water needed for evapotranspiration, from planting to harvest for a given crop in a specific climate regime, when adequate soil water is maintained by rainfall and/or irrigation so that it does not limit plant growth and crop yield”. “Although the values for crop evapotranspiration and crop water requirement are identical, crop water requirement refers to the amount of water that needs to be supplied, while crop evapotranspiration refers to the amount of water that is lost through evapotranspiration” (Allen et al. 1998).
Reference: [Allen et al. 1998; ICID, 2000]

Publications / information

• Lee, T.S., Najim, M.M.M. and M.H. Aminul, 2004:
  Estimating evapotranspiration of irrigated rice at the West Coast of the Peninsular of Malaysia. -
  Journal of Applied Irrigation Science, Vol. 39. No 1/2004, pp. 103 - 117.
  VL reprint under:
  VL Irrigation & Hydrology - vl_ref_id_x_0004 ⁽⁾

Reference

• Allen, R.G., 2002:
  Comparison of Cumulative Evapotranspiration at Kimberly, Idaho using Mean Crop Coefficients from Table 6.9 of ASCE Manual 70 for Years of Measurement by Crop and the 1982 Kimberly Penman and ASCE Standardized Penman-Monteith Reference Methods. -
  University of Idaho, Kimberly, Idaho 83301.

• Allen, R.G, Pereira, L.S., Raes, D. and M. Smith, 1998:
  Crop evapotranspiration - Guidelines for computing crop water requirements. -
  FAO Irrigation and drainage paper 56, FAO, Rome.

• Allen, R.G, and Wright,J.L, 2004:
  Evaporation Component of ET Estimated from Daily Lysimeter Measurement at Kimberly, Idaho. -
  Winrock Water Files.

• Burnett, B., Allen, R.G, Robison, C.W, Tasumi, M., and I. Lorite, 2008:
  Estimating the Soil Surface Evaporation and Transpiration Components from Satellite Images in the Absence of a Thermal Band. -
  World Environmental and Water Resources Congress 2008: Ahupua’A.

• Dorenbos, J. and W.O. Pruitt, 1977 and 1992:
  Crop Water Requirements - Guidelines for Predicting Crop Water Requirements. - FAO Irrigation and Drainage Paper 24, FAO, Rome.

• ICID-CIID, 2000:
  Multilingual Technical Dictionary on Irrigation and Drainage. -
  CD Version September 2000, International Commission on Irrigation and Drainage, New Dehli.

• Land and Water Development Division, FAO:
  CROPWAT - A computer program for irrigation planning and management. -
  (free to download), for MS Windows and DOS, FAO, Rome.

• Pereira, L.S., Allen, R.G., Paredes, P., López-Urrea, R., Raes, D., Smith, M., Kilic, A. and M. Salman, 2025:
  Crop evapotranspiration – Guidelines for computing crop water requirements. -
  Second edition, revised 2025. FAO Irrigation and Drainage Paper, No. 56 Rev.1. Rome, FAO.

• USDA, Soil Conservation Service, 1993:
  Irrigation Water Requirements. -
  National Engineering Handbook (NEH), Part 623, Chapter 2, National Technical Information Service.

• WCA infoNET:
  Topic tree and sources: Crop water requirements. -
  WCA infoNET - A Knowledge and Information Dissemination System on Water Conservation and Use in Agriculture, IPTRID/FAO. (discontinued/offline)

Content index

• VL - Thematic index
• VL - Thematic index full