بلومي, فؤاد2026-01-192026-01-192018-12https://dspace.omu.edu.ly/handle/123456789/495Only less than 10% of the entire area of Libya exceeds 100 mm of annual rainfall. Groundwater is the main source of irrigation water, so it is necessary to adopt appropriate measures to provide water for irrigation while working towards achieving the greatest possible increase in water use efficiency. The main aim of this study is to estimate and compare the irrigation water requirements for the same crops cultivated in northern and southern regions of Libya, to select the most important strategic crops to be grown in the less water consuming region, and to use the excess water to cultivate additional land in the less water consuming area to obtain the highest possible production per unit of water. The reference evapotranspiration (ref. ET) and crop irrigation water requirements (CIWR) were estimated using Omar Al Mukhtar University model (OMU-ET 1.0.0). the model was Prepared using Visual Basic 6 software and database programming, for the purpose of estimating ref. ET based on the Penman Monteith equation. the model also calculates the single crop coefficient according to the methodology presented in irrigation and drainage Paper no. 56-FAO; as well as calculating the effective rainfall using FAO method and calculating leaching requirements. The model calculates crop coefficients(Kc) while most other similar models don’t. For the purpose of OMU-ET 1.0.0 model verification, the model results were compared with a number of widely used global models: Aquacrop 6.0, Ref-ET, Cropwat 8.0 and PMmon models. The comparison of the results using 21 years climatic data for several northern coastal stations (Tripoli and Benina) and southern desert (Kufra and Sabha) and taking the mean results in addition to the use of averages climatic data for this period to obtain the monthly results using the "t" test at the level of 0.05. The results of the statistical analysis revealed that there were no significant differences between the results of OMU-ET 1.0.0 model and other models for all years of comparison and for all stations except the results of Cropwat 8.0 model in some stations. Thus the results of the Cropwat 8.0 model were compared with the results of Aquacrop 6.0 and REF-ET models, and the differences were also found to be significant in some stations such as Omu – ET 1.0.0. model. It can be concluded that OMU-ET 1.0.0 is one of the models that can be used with confidence to estimate irrigation water requirements. The results of ref. ET using climatic data from northern coastal stations (Tripoli airport, Benina and Sirte) and from southern desert stations (Kufra and Sabha) were compared and the results showed that there were no significant differences between the stations of the northern coastal region as well as between the two stations of southern desert stations using "t" test and at a level of 0.05. Thus, the average ref. ET was calculated for each region to be its representative. The two representative average reference ET were compared and the differences found to be significant at 0.05. CIWR for northern coastal and southern desert regions were estimated for a number of agricultural crops. The results showed that the CIWR of one hectare of crops in southern region are sufficient to irrigate the same crop area of 2.04, 2.02, 1.67, 1.70, 1.87 hectares for wheat crops, barley, corn, sorghum and alfalfa, respectively.Thesis