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The combined weir-gate is one of the structures, which can be substituted in channels instead of weirs and gates. Curvature of the semi cylindrical of the weir- gate structures lead to hold the water snap to the structures body which increases the amount of coefficient discharge the weir- gate structures in comparison with the sharp crested weirs. In this research, the affection of some dimensionless parameters on discharge coefficient in the semi cylindrical weir- gate model was investigated. The experiments were conducted in a horizontal channel with a length of 8 m and width of 0.282 m through using PVC pipes with diameters of 70, 120 and 160 mm as wire and wire-gates. The research findings show that the coefficient of discharge increases by increasing the dimensionless parameters including H/P, Hw/H, Fr and Hf/H for both upstream and downstream curvatures in all alignments of the structure. Hence, the maximum and minimum discharge coefficients occur in the 60 degree and 30 degree angle, respectively. Also, at a constant H/D and Hw/H, the coefficient of discharges is larger for upstream curvatures than the

downstream ones. The results show that not only the angle of the semi cylindrical curvature from the horizontal line but also the structure diameter affect on the discharge coefficient

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Natural phenomena could be recognize through the selection and then produce the appropriate scale. The critical subject in this way that have been less studied in Iran is identifying the multi-scale algorithms and distinguish them from simplification algorithms. In this research, operation of each multi-scale algorithms at certain scales have supposed, then implementation of structural simplifying algorithms- low pass filter and simple average- in order to identify the flood process using three Digital Elevation Models at 1:25000, 1:50000, and 1:1000000 scales in ArcMap software and HEC-HMS model have evaluated. Results demonstrated that different approaches of map production make different results as the generalization and the best approximation of spatial data. Comparing the result of flood simulation proved sensitivity of such algorithms with respect to scale of base map. It has been specified that the effect of generalization algorithms do not necessarily conform the hierarchical structure of scale of input data. Finally, we suggested to investigate the flood phenomena of Jamash watershed, we should use low pass filter and simple average algorithms to simplify DEMs at 1:25000 and 1:1000000 scales but using these algorithms at 1:50000 scale have not suggested.
 

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The purpose of the modern watershed study is to use a regional pilot to select an erosion sub-basin and restore it to preserve the downstream wetland. In this research, Alanza watershed, located in the upstream reaches of Anzali wetland, has been selected as a sub-watershed (pilot) with the aim of investigating the effect of mechanical, biological and biomechanical operations on modern watersheds. At first, the location of the construction of the watersheds was determined using field operations. Then, due to the planting of species, structural design and also to study the current status of the flow in the river flow modelling channel, using flow and sediment modelling software (HEC-RAS) was used. Using the HEC-Geo RAS extension in the GIS software, the spatial data related to the shape of the river and its longitudinal slope were entered into the HEC-RAS software, and flood flows analysis was calculated. Then, for the design of the structure, the highest score was assigned to the coverage of a mortar coating with a score of 36. Due to the climatic, ecological and environmental conditions of Alanzeh sub watershed for seedling of several forest species, seedlings with ecological conditions of the study area were used.



 

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Co-management of water resources is one of the most important managerial approaches in water resources; its achievement requires the strengthening of social capital; also, the role of water resources Local Stakeholders in increasing the amount of this capital is undeniable. The social network analysis approach is one of the strategies that will examine the pattern of relationships between Local Stakeholders in planning, policy making and successful implementation of participatory water resources co-management. In this research, the social relationships between 143 farmers of Gezir village, Bandar-Lengeh province, which are used by indigenous structures for irrigation of the palm groves, have been investigated using the network analysis and network level measurements (density, Reciprocity and average geodesic distance); The data of this study were collected in the fall and winter of 1396. The results represent the favorable social capital that the optimal amount of this capital derives from the applicability and importance of the indigenous community structures, in particular the cistern structure, for managing water resources through strong links of Consultation (rainfall time) and Collaboration in the affairs related to these structures. Therefore preserving the collective indigenous structures water resources will strengthen social capital and increase Resilience to tensions for water resources co-management.
 

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       This study aimed to investigate the effect of soil physicochemical properties on gully erosion in the Qarranqou Chai watershed located in the south of East Azarbaijan province. Toward this, a rainfed area with 30 km × 30 km in dimensions and affected by gully erosion was selected in the area and gully erosion, morphological characteristics of gullies along with physicochemical soil properties were determined in each grid. Results indicated that gully erosion is ranged from 2.64 to 242.7 ton per square kilometer, with an average of 21.38 ton per square kilometer. It is significantly correlated with sand (r = 0.28), moisture saturation percentage (r= 0.27) and aggregate stability (r= -0.29). Aggregate stability in contrast with two other soil properties appeared negative role in gully formation. No significant correlation was found between gully erosion and silt and soil erodibility factor (K) estimated by the Universal Soil Loss Equation (USLE). This study revealed that aggregate stability is a major soil properties controlling gully erosion in rainfed lands. Maintaining crop residues is the first strategy to enhance soil organic matter content, improve aggregate stability and in consequence decrease the soil’s susceptibility to gully erosion in the area.
 

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In this research, the weir-orifice composite structure was simulated using two water elevations and six analyzes in the Flow-3D model, and the results were validated with laboratory data. Three grid groups were used to select the optimal block mesh. However, the K-Ɛ and RNG turbulence models were used to select the appropriate turbulence model. The block mesh with 198750 cells was selected as the most suitable mesh for this simulation. The results showed that the RNG turbulence model with the correlation coefficient of 0.92 has the highest accuracy and speed. The numerical model investigated the velocity, pressure, water level profile, and flow lines, and the results were presented. Then, by using three water heights of 0.0756, 0.0973, and 0.1243 m and applying ten different angles at each height, by changing the location of the overflow from horizontal to diagonal in the cross-section of the circular channel, changes in the discharge coefficient of the case were investigated. Also showed that the diagonal weir had increased the discharge coefficient. The lowest and highest discharge coefficient values were obtained for angles of 2.5 and 12.5 degrees with values ​​of 0.67 and 0.84, respectively. Weir with an angle of 12.5 degrees with an increase of 13.27% of the discharge coefficient has the most increase in this coefficient among the applied angles.