الفهرس 
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Abstract
Objectives: The main objectives of this study were to create a computer model able to predict the optimal design of micro-irrigation systems. A model named OPT-DOMIS was created using Oracle Developer Suite 10g (forms) and Oracle Database 10g (PL/SQL Language). The model was carried out into five modules as follows: 1- Emitter selection calculations module, 2- Initial irrigation system design requirements module, 3- Economic lateral diameter module, 4- Economic manifold diameter module, and 5- Module of the optimal design among different design alternatives. Methodology & Results : The OPT-DOMIS model was created as a toolbar. This toolbar hosts nine buttons concerning the following: 1-Land area and water resources, 2- Crop or tree data and salinity data, 3- Soil data, 4- Emitter selection calculations, 5- Initial design requirements calculations, 6- Economic lateral design calculations, 7- Economic manifold design calculations, 8- The optimal design calculations at lateral in x-axis and manifold in y-axis, and 9- The optimal design calculations at lateral in y-axis and manifold in x-axis. The results were: 1- The case study was carried to predict the gross water application at different water quality. The relationship was positive which explained that as the water salinity increases the gross water application increases. On the other hands, the relationship was also positive and showed that as the water quality decreases the application time increases to get the plant water requirements plus leaching requirements. As well as the irrigation water salinity increases the percent of potential yield resulting from the salinity decreases. 2- The case study was tested on different soil types (clay, loam and loam sand) which was planted by trees (banana, grape, apple, pear and mango). The clay soil was the least need for emitter discharges, the emitters discharge rate in loam soil were more than clay soil and the sandy loam soil was the most need for emitter discharges. The emitter discharges in clay were from 2.75 L/h to 28.5 L/h while the emitter discharges in loam sand were from 1.14 L/h to 11.86 L/h. 3- To design the lateral, the case study was done in the area of 120 m × 160 m, so the length of 120 m was assumed as the x-axis of the area, while the length of 160 m was assumed as the y-axis of the area. At the x-axis direction, the lateral lengths were 58 m at lateral diameters. The optimal inside diameter was 13.6 mm because it has the least annual cost which was 0.229 L.E/m/year. While the percent of pressure head variation with optimal diameter was 15.45 %, which is considered in the direction of x-axis. 4- To select the optimal design of different design alternatives, the case study was carried on different areas. The areas were 5.71fed. The results showed as follows: The optimal design of one area was alternative. This design was the lateral in x-axis but manifold in y-axis. The total annual cost of this design was 4467.41 L.E/year as well as pump power was 1.71 hp. Also, the total area was divided 1 subunit in x-direction and 3 subunits in y-direction plus the irrigation time was 14.4 h/day. Conclusion: The OPT-DOMIS model is preferably to be used by irrigation system designers because it contributes to a specific decision rather than alternatives solutions, i.e. the designed model would provide an opportunity for the farm owner to select the optimal and economical solution according to the available alternatives.