evaluation of the efficiency of cropwat model for determining plant water requirement in arid regions

shortage of water resources and increasing demand to consumption of this scarce resource, leads to somenoticeable limitations. on the other hand, population growth and consequently, increasing demand for water in aridand semi arid regions , needs production in exchange of little amount of water consumption. to approach thisobjective, an experiment in the complete randomized blocks carried out in four replications for cumin plant growingin zabol, southeastern iran. experimental treatments included irrigation periods at three levels. then usingcropwat model, the water requirement of the plant is met. analyzing the data resulted from production gatheredin different times of irrigation and consumption of water in the three times irrigation case with sound efficiency (1750m3/ha), is more little than the water amount which is simulated by the cropwat model in 2003 (6070 m3/ha) and(5363 m3/ha) in 2004. it then showed that this model is not effective in determining the water requirement of cumin atthis region.