Twoexperiments were conducted at Sakha Agriculture Research Station, during the two successive summer growing seasons of 2012 and 2013 to estimate and analysis water requirements components for some Egyptian rice varieties (Oryza sativa L); namely cvs. Giza 178, Sakha 102 and Sakha 104 and to evaluate and compare the estimated rice crop evapotranspiration (ETc) values computed using Hargreaves, Penmen-Monteith and Class A pan methods used for (ETc) with the measured actual rice evapotranspiration (ETa) using micro- paddy lysimeter used for (ETa) to evaluate the best method for estimating the reference evapotranspiration which suitable with North Nile Delta conditions.
Results showed that evaporation (E) is the highest component of total rice water requirements (WR) during the whole growing season stages for cv. Giza 178 with an average 39.8%, followed by cvs. Sakha 102 and Sakha 104 with an average 38.3 and 38.2%, respectively. However, Transpiration (T) is the lowest part of WR for cvs. Giza 178, Sakha 102 and Sakha 104 with an average 21.0, 20.1 and 21.4%, respectively. For percolation (P) is major for Sakha 102 and Sakha 104 varieties with an average of 41.6 and 40.4%, respectively. Meanwhile, the lowest value of P (39.2%) was lost from Giza 178. Mean values of ETa for cv. Giza 178, Sakha 102 and Sakha 104 were 6.1, 6.0 and 6.0 mm day-1,respectively. Although mean values of the estimated rice crop evapotranspiration resulted from Hargreaves, Penmen-Monteith and Class A pan methods were underestimated actual rice evapotranspiration, but Hargreaves and Penmen-Monteith methods performed best for North Delta, Egypt because of the least amount of error and least percentage deviation between ETa and ETc. Crop water productivity (CWP) were 0.85, 0.86, and 0.87 Kg m-3 for rice cvs. Giza 178, sakha 102, and Saka 104, respectively. Also results indicated that the values of crop water use efficiency (CWUE) of rice for cvs. Giza 178, Sakha 102 and Sakha 104 were 1.53, 1.55 and 1.46 Kg m-3 respectively. So, Hargreaves and Penmen-Monteith methods could be recommended for saving irrigation water with planting rice cv. Giza 178, which gave higher water productivity.