فصلنامه مهندسی منابع آب
پیاپی 44 (بهار 1399)

In the present study, a laboratory comparison of increasing the number of porous obstacle rows and two porous obstacles with a distance of one meter is considered as a permeable obstacle for controlling turbidity current in different heights. Plastic cubes with dimensions of 2.1 (cm) with surface porosity of 25% have been used. The flume slope range was ± 2.5%, a length of 10, a width of 0.3 and a height of 0.45 m. The flow rate was 0.7 L/s and the input concentration was 20 g/L. The results of the investigations showed in the porous obstacle with the simultaneous flow of condensate in two directions perpendicular to each other, the flow lines encountered in the porosity and by creating a flow in porosity, cause more depletion of the energy of the current flow from within would be. The use of two obstacle rows reduces the height of the obstacle to control the current flow. Also, in the case of two obstacles with different heights, obstacle with higher elevations initially causes more deformation of the current. In steady state, due to the increase in the momentum of the flow, a greater part of the sediment passes through the first obstacle, which makes the effect of the second obstacle more effective in controlling the current flow in this state than the non-slope state. Also, with increasing number of rows, the performance of the porous obstacle increases and the performance of the two obstacles is longer than the thickness of the performance.

The construction of the hydropower plant on the water pipelines using the excess pressure and replacement of PAT instead of the pressure reducing valve (PRV) due to positive effects such as renewable energy, the proper dispersion of water supply pipelines in different regions and short production time are considered. On the other hand, the prioritization of the construction of the power plant on the water pipelines involves various factors, which require multi-criteria decision-making methods. In this research, the water pipelines managed by the water and wastewater company of Ilam province, including six positions, taking into account five indicators, electricity production, construction costs, distance from the place of use, distance from the main road and ease of operation using multi-criteria methods (including: hierarchical analysis, network analysis, simple weighting, VIKOR and similarity to ideal option and economic analysis). The results indicated that the entrance to the Station 1 of the Ilam Dam (with an annual production capacity of 982800 kWh, the construction cost of 1218 million Rials, with a benefit-cost ratio of 3.7 and unit cost of 407 Rials per kW) is the best alternative for the production of hydro-electrical energy.

Well designed monitoring networks are essential for the effective management of groundwater resources but the costs of monitoring well installations and sampling can prove prohibitive. Principal Component Analysis (PCA) is one of the data reduction techniques used to extract the important components that explain the variance of a system. In this paper, the PCA was used to identify the effective wells and remove the less important ones. For this purpose, 160 wells were constructed in the Salman Farsi agro-industry, which was measured twice in a month during 10 months. In this technique, variation factors called principle components are identified with considering data structures. Using the PCA, the relative importance of each well was calculated for groundwater depth estimation. In the present study, the acceptable threshold was taken to be 0.8, according to which the number of wells in determining groundwater depth was reduced to 33 wells. By identifying important wells, important points for sampling are identified, and groundwater depth monitoring is performed only in these wells. As a result, it can save a great deal of time and cost of studies.

Base-flow is the percentage of river flow which is associated with groundwater discharge and demonstrator of the extent of groundwater participation in total runoff. Therefore, base-flow has an important role in hydrological and water resources researches such as quantitative and qualitative water resources assessment, hydrologic modelling, calibration and validation of these models and also evaluating the environmental water requirements in different regions. In present research the daily data of river flow for the period of 30 years is selected to evaluate base-flow in Shamkan River which is located in Sangerd catchment. The daily base-flow is calculated during the years of 1987 to 2016 using BFI, Lyn and Hollick, Eckhart and Local Minimum methods. Due to the lake of observation base-flow data, the BFI method is considered as the base method and the results of other methods were compared with the results of the mentioned method. The results indicated that the estimated base-flow by different methods is averaged between 71 to 81 percent of the river flow. The results of error criteria showed that Lyn and Hollick method with the filter parameter of 0.95 is the most suitable method to separate base-flow in the case study. While the Eckhart method with the filter parameters of 0.99 and 0.995 have had highest RMSE and MAE values and also had the lowest Nash-Sutcliff values.

Horse-shoe vortex at the bridge pier nose is a final result of reverse pressure gradient at the upstream side of pier and river surface. From literature review different ideas about the formation and initiation of horse-shoe vortex at the bridge pier can be found. These ideas indicated that the horse-shoe vortex is formed before the formation of scour hole, exactly when the scour hole forms and after the formation of scour hole. In present study these ideas are examined with different experimental data selected from previous studies. The experimental data includes equilibrium scour hole to examine the size of horse shoe vortex in comparison with final scour depth and time development of local scour depth to study the variation of horse-shoe vortex diameter with time. Results showed that similar to scour depth development, the logarithmic trend of horse-shoe vortex diameter with time tends to an equilibrium value. In addition, the calculated horse-shoe vortex diameter in equilibrium scour hole condition with different methods is a function of different parameters such as sediment size or bridge pier diameter and varies from 0.3 to 3.3 of equilibrium scour hole. Finally, a new method is presented for calculation of bed shear stress at the bridge pier with regard to diameter of horse-shoe vortex. In this method, by increasing the size of horse-shoe vortex, shear stress at the bridge pier decreases from 4 times of upstream shear stress to critical shear stress of stream bed sediment.

Particles which transfer is effected by raindrop splash depends on several factors, including soil type and rainfall intensity. Although information on the role of these two factors in splash erosion is available, but the selectivity of particles in splash erosion is unknown. This study was conducted to investigate the effects of splash erosion and selectivity of particles in different soils under the influence of rainfall intensity. For this purpose, experiments were carried out in three different soils (Loam, Clay loam, Sandy clay loam) on tree rainfall intensities (10, 20 and 30 mm.h-1) under a constant slope of 10 % in three replications, with a total of 27 units in the form of a completely randomized design was done. According to the results, the highest and lowest amount of splash erosion in the soil were clay loam (80.45 g.m-2.min-1) and sandy clay loam (62.19 g.m-2.min-1), respectively. With increasing rainfall intensity, the intensity of splash erosion increased. In general, the selectivity of particles in the splash erosion is affected by the soil texture rainfall intensity and the interaction between of them. Sand, silt and clay particles were 3.23%, 59.70% and 37.07% of the share of splash particles. In all textures (except the loam texture), the selectivity of the silt particles at different levels of the gradient was greater than the rest. In the loam soil, clay particles were more selective than silt particles, due to the low clay particles in the initial soil sample.

Effective strategies for optimal management of water distribution networks (WDNs) along with financial resources are clearly identifying design and performance parameters affecting the emergence of non-revenue water and reducing the impact of parameters. In this study, using references and experiences of experts in the field of WDN, the factors that are involved in the development of non-revenue water components were identified. Then, to collect the required information on the status of the parameters, officials’ and experts’ opinion were asked through questionnaires. Bayesian Networks (BNs) were used as a modeling tool so as to not only consider uncertainties associated to the lack of sufficient data and detailed information on non-revenue water components but also consider the probabilistic relationships between parameters. Finally, in order to analyze BN models results, a sensitivity index was proposed to prioritize parameters based on their impact. To investigate the usefulness of the proposed model, the area covered by District 4 of Tehran Water and Wastewater Company was selected as a case study. The results indicated that the probability that apparent losses, real losses and non-revenue water are high is 37.48 %, 35.04% and 32.2%, respectively.

 In recent years, the increasing growth of population and economic development aroundthe world is leading to rising demand for limited resources, and this issue has caused environmental conflicts in the exploitation of common resources. In such situations of conflict, to achieve fair allocation, numerous mathematical tools associated with different theories can be used. A systematic understanding of the interactions between individuals and groups of beneficiaries in environmental conflicts can help to create strategic and effective solutions in order to manage resources, and better policies can be offered by using these theories. Bankruptcy theory is modern, functional and highly flexible theory. Therefore, in this study, by using different methods of bankruptcy theory including Proportional (PRO), Constrained Equal Lost (CEL), Pinile (Pin), Constrained Equal Awards (CEA), Adjusted Proportional (AP) and Talmud (TAL), allocation of surface water of the Urmia Lake basin among three provinces including East Azerbaijan, West Azerbaijan and Kordestan, was investigated by considering provided minimal environmental requirements of Urmia Lake, (3100 million cubic meters) and the results of the different methods were compared. Based on the results of this study, the CEA method provides the maximum allocation for the two provinces, Kurdistan is 100 percent and East Azarbaijan is 93 percent and satisfies the two provinces from the three provinces more than other methods. Therefore, based on the Plurality rule, the CEA method in this study was selected as the preferred method.

Physical processes are dependent on various parameters that are modeled in their mathematical language with their own equation. Since some nonlinear partial differential equations are so difficult to solve, hence obtain their analytical solution except in certain conditions is not possible and such equations can be solved numerically. The equation that is considered in this research is the Burger equation in time-dependent nonlinear two-dimensional mode, which models the phenomenon of velocity of falling of particle in the stagnant or near-stagnant fluid, such as sedimentary water behind a dam. In this research, first, this equation discretized using the fully implicit finite difference method to solve the two-dimensional Burger equation, which is an unconditional stable method, then it programmed. Also, the accuracy of the equation solution results with another numerical method (finite element method) is compared which implies the consistency of the simpler method of finite difference to the more complex method of finite element. Numerical results have been obtained for different viscosities and times, and their role in the particle velocity has been examined parametrically. Generally, the results showed that increasing viscosity and time, lead to decreasing in fall of the particle velocity. Within the increasing the time, locus of the maximum velocities approach to the bottom of the bed and the end of the length in the depth and longitudinal directions, respectively. Also, the negative depth velocity (upward flow) was observed, especially at the edges near the bed, indicating that the particles are suspended in some positions and times.