Gezira Scheme has a major impact in Sudan economical and social life since it has been established in 1925 . Scheme recently faced many seasonal water shortage that lead to conflict between stakeholders and reduction in the scheme benefits due to canals siltation and weed infestation, caltivation of areas that is beyond the capacity of canals to deliver , lack of accurate data base of indenting water for crops and weak coordination between different scheme partners. In this study a comparison of three different methods for predicting crop water requirement has been carried out considering Wad Medani Climate. These methods are Blaney-Criddle method , Hargreaves-Samani model and FAO Penmann Monteith model. The results showed that average annual evaportranspiration, ET0 for these methods were 5.79 mm/day, 6.2 mm/day and 6.64 mm/day respectively The Crop Water Requirements (CWR ) per season were found to be for crops cotton , sorghum , groundnut, wheat and vegetables 4236.2 m3 ,2393.2 m3 , 2926.9 m3 , 2689.9 m3 , and 7079.5 m3 respectively with actual CWR daily average 21.5 m3 per fedan. However in contrast the average water productivity were found to be for crops cotton , sorghum , groundnut, wheat and vegetables 23 SDG/ m3 , 40.1 SDG/ m3 , 37.8 SDG/ m3 , 72.5 SDG/ m3, and 118.7 SDG/ m3 respectively .