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This study was conducted to estimate the evapotranspiration and to probe the seasonal groundwater contribution in total crop water use by the sesame crop under different water table depths. The method of combining lysimeter was executed to investigate the groundwater contribution in total water used by the crop. The water table depths were maintained at 1.60, 2.0 and 2.40 m, respectively. Each water table depth was replicated for three times. Climate conditions under which crop was grown were monitored and all the water balance components were recorded accordingly. The obtained evapotranspiration (ET) from lysimeter experiment was compared with the predicted ET by CROPWAT model. The experimentally observed ET were 457.5, 452 and 428 mm under the water table depths of 1.60, 2.0 and 2.40 m, respectively. The predicted ET using CROPWAT model was 434 mm, which was very close to the observed values. Under the lysimeter experiment, the groundwater contribution in total crop water use was observed as 37%. The predicted crop coefficient was ranged from 0.38 to 0.98, whereas the experimental crop coefficient was 1.0. The trend of soil moisture balance predicted by the model revealed the same as that experimentally observed. Thus, the use of CROPWAT model is recommended to redesign irrigation amounts and to prevent soil salinity and waterlogging problems. [ABSTRACT FROM AUTHOR]