Actual and Predicted Evapotranspiration Along with Groundwater Contribution for Wheat Crop

This experiment aimed to determine the crop evapotranspiration (ETc), groundwater input in total water used by wheat crop, and to simulate the CROPWAT model to envisage the crop evapotranspiration rate. To estimate on-field ETc and groundwater contribution the combining lysimeter technique was used. The water levels below the soil surface were kept at 1.60, 2.20, and 2.80 m and each water table depth was replicated three times. The experiment was conducted under silt loam (SL) and silty-clay loam (SCL) soil conditions. The climatic parameters and water balance components were recorded accordingly. The on-field ETc was compared with the predicted ETc by CROPWAT model. Under SL soil, the observed ETc was 442, 427, and 401 mm at the water table depth of 1.60, 2.20, and 2.80 m, respectively. The recorded ETc under SCL soil was 419, 402, and 389 mm at the same water table depths, respectively. The ETc reduced with an increase in water level below the surface. The groundwater contribution at 1.60, 2.20 and 2.80 m depth of water level under SL and SCL soil was observed as 50, 41, and 30 % and 43, 34, and 24 %, respectively. The predicted ETc by CROPWAT model for SL and SCL soil conditions was 428.8 and 410.7 mm, respectively. The projected ETc is likely equal to the average ETc observed under lysimeter experiment. Thus, the use of CROPWAT model is recommended to overcome waterlogging and salinity problems and to conserve water resources

Assessing evapotranspiration rate and sesame (Sesamum indicum) crop water use under different water table depths

This research was intended to determine the groundwater contribution in crop water-use of sesame crop under different water tables depths and to assess the accuracy of CROPWAT model to simulate the evapotranspiration. The method of combining Lysimeters was implemented to investigate seasonal groundwater contribution to crop-water use. The climatic conditions under which crop was grown were monitored, water table depths were maintained (at 1.60 m, 2.0 m and 2.40 m) and all water balance components were measured. The crop coefficient (Kc), ET and reference evapotranspiration (ETo) were determined. The obtained results were compared with the outputs of the CROPWAT model. The results reveals that, the average ET of sesame crop under lysimeter experiment was about 450 mm which was slightly increased under increased water table depths. Around 40% of groundwater contribution was recorded in overall crop-water use. The crop coefficient values were exceeded above 1.0 due to high foliage, developed through better canopy cover. The average water use efficiency was observed as 21 kg/m3. The predictions of CROPWAT model were virtually same as observed in the lysimeter experiment. The total ET was predicted as 434 mm, the predicted crop coefficient were ranging from 0.38 to 0.98. The soil moisture balance predicted by the model reveals the same trend of soil moisture balance as observed in the field. The predicted irrigation schedule was also resembling the same trend of irrigation applications as observed under lysimeter experiment. Thus, the utilization of CROPWAT model is durably suggested to be used as management tool to overcome the salinity and waterlogging problems caused by over irrigation events