الفهرس 
Simulation modelsOnly 14 pages are availabe for public view
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Abstract
The study aimed to build up and validate GPIMOD simulation model to predict water distribution under traditional and modified (SCGO) gated pipe irrigation technique. Another main objective was to study the hydraulic performance analysis of self-compensating gated outlet (SCGO) 50 mm outlet diameter. As well as, field evaluation for modified gated pipe irrigation technique compared with traditional. It was carried out using two P.V.C pipe lines of 110 mm diameter and 50 mm outlet diameter. The effect of both irrigation technique on soil moisture content, crop yield, dry matter and water productivity of potato were studied under three outlet spacings (0.7, 1.0 and 1.5 m) during two successive seasons 2011-2012 and 202-2013 on clay loam soil at Shalakan Farm, Faculty of Agricultural, Ain Shams University, Kalubia, Egypt. The field experimental results were used in calibration and validation of the SALTMED simulation model. The main results in this study are summarized in the following points:
5.1 Design of GPIMOD simulation model
GPIMOD is a computer tool for the simulation of gated pipes commonly used for flood irrigation. Three options that are available for the user of Primary (fixed) conditions input head, average outflow and total outflow. After the user has selected the primary conditions will go to the next tab to input the system information, supply, pipeline and outlets in the interface. The program processing the data to simulated the out flow. Users can chooses the data output, on click simulation and facility to print, on click on any gate show details of gate, print and save in Excel or pdf files.
5.2 Hydraulic analysis of self – compensating gated pipe
5.2.1 Hydraulic performance of (SCGO)
A- Performance analysis of designed components The discharge was measured for self-compensating gated outlet. In general there was slight variation in discharge for SCGO under pressure in the range 0.01 – 0.28 bar. The average of discharge was kept around 0.52 l s-1 for 50 diameter. That reflect the effect of compensation action caused by grooved disk and rubber diaphragm on discharge regulation. The developed gate outlet became compensating at pressure head from 0.06 to 0.28 bar.
B- Gate discharge and Coefficient of variation
The manufacture coefficient of variation was 0.09 % of 50 mm diameter when gate outlet discharges 0.52 l s-1 at pressure range from 0.06 to 0.28 bar.
5.2.2 Field Measurements and Calculations
A- Discharge along pipeline under different operating pressure for traditional gated pipe
The discharge (l s-1), under different operating pressure (bar) for traditional gated pipe with 0.7 m spacings between the gates, 110 mm pipeline diameter, and 50 mm outlet diameter. The average observed data of discharge for first and last gate for traditional gated pipe was kept around (2.8, 4.9 l s-1), (3.9, 6.9 l s-1), (4.9, 9 l s-1), (5.14, 9 l s-1), (5.63, 10.42 l s-1) and (6.18, 11 l s-1) under operating pressure (0.08, 0.12, 0.16, 0.2, 0.24 and 0.28 bar) respectively. The trend observed for discharge l s-1, with 1.0 and 1.5 m spacings between the gates were a similar for the discharge l s-1, under with 0.7 m for traditional gated pipe under different operating pressure bar.
B- Discharge along pipeline under different operating pressure for modified gated pipe
The discharge L s-1, under different operating pressure bar for modified gated pipe with 0.7 m spacings between the gates, 110 mm pipeline diameter, 50 mm gate diameter. The average observed data of discharge between first and last gate for modified gated pipe was kept around (2.64, 2.59 l s-1), (3.22, 3.09 l s-1), (3.88, 3.76 l s-1), (4.2, 4 l s-1), (4.82, 4.69 l s-1) and (5.2, 5.06 l s-1) under operating pressure (0.08, 0.12, 0.16, 2, 2.4 and 2.8 bar) respectively. The trend observed for discharge l s-1, with 1.0 and 1.5 m spacings between the gates were a similar for the discharge l s-1, under with 0.7 m for modified gated pipe under different operating pressure bar.
C. Uniformity coefficient
Distribution uniformity coefficient (DUC) along line of traditional and SCGO gated pipe it was found 82.7% and 96.3% respectively.
5-3 Validation GPIMOD simulation model
The outflow and pressure head at every gate of gated pipes irrigation [110 mm diameter, gates circle shape 50 mm diameter, 0.7, 1.0 and 1.5 m spacings along pipeline were measured under field conditions to validate the GPIMOD simulation model Version 1.1 (Gated Pipe Simulation Model 2015). The latter is a computer simulation model for the design of gated pipes as used for furrow irrigation, depends on mathematical water flow hydraulics models.
Data of verification and validation for GPIMOD under gated pipe, gave a good indication of the model’s ability to predict and estimate outflow from gates. The high values of the coefficient of determination R2 reflected a very good agreement between the model and observed values. It can be concluded that Using of GPIMOD simulation model is acceptable for predicting water distribution uniformity for gated pipes irrigation technique, water distribution uniformity for furrow irrigation to maximize irrigation water productivity.
5.4 Soil moisture content
Results indicated that the regulated irrigation using modified gated pipe leads to an increase in soil moisture and subsequently an increase in the yield in comparison traditional gated pipe. The results indicated that there was slight variation in soil moisture for 0.7, 1.0 and 1.5 gate spacings during the initial growth stage, but under 1.5 m gate spacings there was more variations in soil moisture especially during the mid and end growth stages in comparison with 0.7 and 1.0 m gate spacings for traditional and modified gated pipe.
5.5 Potato yield and water productivity
The spacings between gates has an effect on yield under modified gated pipe irrigation. The gate spacings of 1.5 m had relatively higher yield in both irrigation techniques with the modified gated pipe being higher than the traditional one. The results also indicated that using 1.5 m gate spacings for traditional gated pipe gave the highest yield (22.09, 22.33 ton ha-1), 1.0 and 0.7 m gate spacings gave the lower yield (19.75, 20.39 ton ha-1) and (17.4, 18.14 ton ha-1) during two seasons respectively. Applying modified gated pipe improved water productivity for two seasons, the highest WP (4.26, 4.97 kg m-3) for two seasons respectively, were associated with 1.5 m gate spacings. On contrast, the lowest WP (2.67, 3.23 kg m-3) for two seasons respectively, was associated with the traditional gated pipe, 0.7 m gate spacings. In addition, there were small differences in dry matter under different gate spacings for both irrigation techniques.
5.6 Calibration and validation SALTMED model
The SALTMED model was calibrated and validated for soil moisture, yield and total dry matter of potato for two irrigation techniques and three spacings. , SALTMED as a holistic model was able to simulate with good accuracy the growth of potato over clay loam soil in Egypt. The SALTMED model proved its ability to predict soil moisture availability, yield, water productivity and total dry matter for two growing seasons under gated pipe irrigation. The results confirmed that the model is able to handle several hydrodynamic processes acting at the same time in the soil–crop–water–atmosphere continuum. Good model estimation of soil moisture has practical implications, it means that the model is able to estimate the amount of irrigation supply required to bring the soil moisture profile from a given soil moisture to a desired soil moisture to maximize the crop yield. In addition, the model now after being successfully tested can be run with “what if scenarios” depicting a variation of gate spacings to select the best one to apply in the field without the need for extra field trials.
Generally, using simulation models is a good tool to estimate the expected net return of irrigation. Using GPIMOD simulation model is acceptable for predicting water distribution uniformity for gated pipes irrigation and water distribution uniformity for flood irrigation. The results indicated the SALTMED model was to simulate with good precision, soil moisture.