مجله آبیاری و زهکشی ایران
سال هفتم شماره 3 (پاییز 1392)

Optimal design of water distribution system is a real problem and its aim is finding the best solution for transferring of water from the reservoir to consumers;so that, all their needs to be supplied with the lowest cost. Many researchers proposed various researches such as linear, nonlinear programming, global optimization,and evolutionary algorithms for minimizing the cost of these systems. The Particle Swarm Optimization (PSO) algorithm, which is an evolutionary algorithm originally introduced for solving optimization problem with continuous variables, but later it was developed for problems with discretevariables. Inthis research, for minimizing the cost of waterdistribution system design after modifications in continuousPSO algorithm, the program was linked to the hydraulic simulator (EPANET 2.0 in Matlab environment). Finally, for improving the algorithm performance, and obtaining the best values of PSO in optimization and water distribution system design, we were used three benchmark networks from previous studies that are different in layout and also the number of pipes, which they called Two-loop, Hanoi, and Kadu networks. From Two-loop network optimization, the least-cost network was estimated from 3100 number of objective function evaluation, which caused to improve the results, when compared to the pervious algorithms. In Hanoi network, the minimum cost was obtained $6.097×106 with =10.667 value, which was less than the results of other networks. Additionally, in Kadu network the cost was obtained 130,666,043 Indian rupees, which was less when compare to the other methods. The results showed a good performance of this algorithm when compared to the other algorithms.

Decreasing of fresh water resources and increasing competition for water by industrial, agricultural and urban users has been enlightening the needs for using of systems with the least water losses. Drip irrigation system has the least water losses as deep percolation and Evaporation. Dimension of wetting pattern is the most important factor to control deep percolation. Several models have been improved to predict the dimension of wetting patterns. In this study, the accuracy of several approaches used to estimate wetting zone dimensions was evaluated. This models including the numerical Hydrus 2D/3D model, the analytical WetUp software and two empirical models including Amin-Ekhmaj and Schwartzman -Zur. The average of RMSE for both directions was 8 percent for Hydrus 2D/3D, which showed that this model has very good accuracy. The ability of analytical WetUp software to estimate the depth and radius of wetting front was good and poor with 16 and 32 percent of RMSE respectively. Amin-Ekhmaj model has a good accuracy with 13.5 percent average RMSE and finally Schwartzman -Zur estimation of the wetting shape were not satisfactory.

One of the ways for forecasting wetting front and moisture in different points of irrigated soil is to use operational models. Nowadays، according to water resource deficiency، no-tillage system is regarded by many engineers because of its high water applying efficiency. In this study، the performance of HYDRUS-2D has been assessed for a no-tillage system. Hence، in 2007، a field under a corn crop and irrigated with tape in Montpellier، France has been considered and soil moisture at different depths measured by a neutron probe in different depths before and after irrigation in mentioned field for a month and was compared with simulated moisture according to two statistic indexes، i. e. RMSE and EF. Results indicated that the model can simulate satisfactorily soil moisture under no-tillage system، after irrigation by exhibiting that RMSE values are o. o11 and 0. 023 (cm3/cm3) and the efficiency factor of model are 96% and 87% at first and end of simulation period، respectively. Coefficient of determination values were calculated too، being in average 0. 96. All in all، it can be concluded that the performance of HYDRUS-2D in simulating soil moisture under no-tillage is very good; so this model can be used in irrigation management in no-tillage.

Given the important role of groundwater resources in the regional water demand، evaluation، simulation and management of groundwater is important. Qazvin plain is bowl-shaped and due to approaching marl formation near to the ground surface at the plain terminal point، it can not be considered as a suitable outlet. Rising of groundwater level and marshy soil in the output of Qazvin Plain is one of the major problems of salt marsh edge. In national plan of salt marsh lands drainage in Qazvin in order to decrease the water table and to prevent the progress of salinity، An interceptor drain with Hydrulic structures have been constructed with a length of 30 (km)، and 99 observation wells، in the direction perpendicular to the drain is constructed in 9 sections. By using monthly water table data in this wells and hydraulic behavior simulation of aquifer of changes water table by using PMWIN model، drain performance on reduce of the water table has been checked. Statistical indices of RMSE=0. 622، MAE=0. 476، SEE=0. 238، R2=0. 85 and error variance of total stress period of 0. 127 are all indicating the accuracy of model output. According to the contain results، decrease of water table up to 60 (cm) of ground surface، leading to reduce of the soil salinity progress that shows drain performance has been quite satisfactory.

The matrix of root and soil increase the soil shear resistance. Therefore trees on beech increase stability of the riverbank. In this study، the Wu model has been employed to calculate the increase shear resistance. To apply this model، determination of the root tensile strength is required. The aim of this study is to investigate the tensile strength of populous tree root and the effects of flow and slope on tensile strength. Six trees (from POPULOUS species) which grow on the river beech were selected in a distance about one km on Saimereh River in IlamProvince. Circle profile trenching method was employed to obtain characteristics. The trench was divided in four quadrants and sampling was performed in each of them. The roots were placed in 15% alcohol solution. Hundred and twenty eight root tensile tests were performed، 64. 1% of which were successful. The problem of root rupture and scrip in between the clamps were noticeable. The minimum and maximum root diameters were 1 and 7. 9 mm respectively and the average root tensile strength was 25. 9 MPa. Non parametric methods were employed for data analysis. Results show that there is no significant difference between the average root tensile strength on up and down slope and also indirect of stream. Although the effect of flow and slope on root‘s tensile strength is slight، the effect of slope is more than flow. Also، the average root tensile strength for each tree is significantly different. In conclusion، the results suggest that it is likely that the environmental conditions and genetic characteristics of trees، to effect on tensile strength.