Revealing climatic changes in reference evapotranspiration in Kermanshah province using the water requirement system

Document Type : Research Paper


1 Soil and Water Research Department, Kermanshah Agricultural and Natural Resources Research and Education Center, AREEO, Kermanshah, Iran.

2 On-Farm Water Management Department, Soil and Water Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran.

3 On-Farm Water Management Department, Soil and Water Research Institute, Agricultural Research and Education Organization (AREEO), Karaj, Iran


Climate changes that have occurred in recent years require that its effect on reference evapotranspiration be investigated as an important factor in determining the crops water requirement. The purpose of this research is to determine the temporal variations of reference evapotranspiration and the factors affecting it in 10 synoptic meteorological stations of Kermanshah province. The meteorological data used include minimum and maximum temperature, average temperature, minimum and maximum relative humidity, wind speed, net radiation input to the surface, and daylight hours in the statistical period of 1999 to 2022. The water requirement system of plants which is the result of the Penman Monteith method of FAO was used to determine the reference evapotranspiration. Pettitt's test of XLSTAT software was used to determine the possible changes in reference evapotranspiration and climatic factors affecting it. The results showed that the climatic variables affecting the reference evapotranspiration are changing. Also, the changes of monthly and annual reference evapotranspiration time series were significant in 42 and 60% of the studied stations, respectively, at the 5% probability level and indicated the existence of a sudden change in these variables. The meteorological station of Gilan Gharb had sudden incremental changes in reference evapotranspiration in all months of the year. On an annual scale, the stations of Eslamabad-e-Gharb, Kermanshah, Gilan Gharb, Javanrud and Hersin experienced this change, so that the Gilan Gharb station had the highest amount of this change with 429 mm. Incremental changes in reference evapotranspiration indicate an increase in the water requirement of plants. Therefore, water resources should be providing to the agricultural sector with a more appropriate planning.


Main Subjects

  • Receive Date: 12 December 2023
  • Revise Date: 21 April 2024
  • Accept Date: 27 April 2024
  • Publish Date: 27 April 2024