مجله محیط زیست و مهندسی آب
سال سوم شماره 1 (بهار 1396)

Increasing the emissions of greenhouse gases is among the factors affected the speed of occurrence of climate change during recent decades. In present study, first using time series data of 2006-2012 and RCM-PRECIS simulation model, the impacts of greenhouse gases emission on climatic variables of temperature and precipitation was investigated under different scenarios in watersheds of Qazvin Province. Then, the ordinary least squares (OLS) method and regression analysis were used to assess the impacts of climatic variables of temperature and precipitation on the selected products yield. Afterwards,considering the results of regression analysis in positive mathematical programing (PMP) model, the amount of the created variation in supply and demand of irrigation water and agricultural output in watersheds of Qazvin Province was investigated. The results showed that emission of greenhouse gases under scenarios A, B, and C affects the climatic variables of temperature and precipitation about 0.43 to 1.27 °C and -14.1 to 1.31 mm respectively. This case changes the selected products yield in the surface of each river basin of Qazvin Province. Change in yield affects acreage of agricultural crops by about -10.51 to 3.17 percent, the amount of irrigation water supply by about -10.4 to 1.64 percent, and the amount of irrigation water demand by about 1.60 to 7.35 percent. Moreover, the results showed that maximum and minimum decrease in the gap between supply and demand of irrigation water happens in Kharroud and Shahroud watersheds by about 9.20 and 1.82 percent respectively. With estimating the gap between demand and supply of irrigation water, one can adopt the appropriate decisions for sustainable water resources in watersheds of Qazvin Province.

Due to the lack of drinking water resources and their importance in the economy of any region, it is vital to locate most suitable place for water storage and water harvesting. Hence, this study was conducted to determine the appropriate places of conservation dams through applying heuristic methods of optimum like AHP and ANP methods in Torghabe and Shandiz located in Khorasan Razavi Province. Selection criteria in this research were five parameters including reservoir volume, reservoir damage, runoff, location, and geology. The research found that eight points in Torghabe and four points in Shandiz have good potential for constructing water reservoir structures. Thus, in Torghabe, a point having higher runoff and reservoir volume compared with the other points was considered as the best place for dam construction. In Shandiz, a point having the highest rating location and geology was proposed as appropriate location for construction. The results showed although ANP method is more advanced than AHP method, both methods have equal value in selecting the best option for constructing the water reservoir.

Nowadays, one of the most important environmental pollution is heavy metals industrial wastewater. Among the various types of heavy metals, chromium is one of the hazardous and toxic environmental pollutants. In order to prevent damage caused by chromium, it seems essential to prevent its entrance to the environment. The purpose of this study was modelling chromium removal using iron oxide nanoparticles through artificial neural network model for estimating the best removal Cr(VI) model. The optimum conditions (more than 90% removal efficiency) achieved were at pH=3, initial concentration of Cr = 10 mg/L; dosage of Fe2O3 = 1 g/L; contact time = 60 minutes, and temperature =25 . After backpropagation (BP) training, the ANN model was able to predict adsorption efficiency with a tangent sigmoid transfer function (Tansig) at hidden layer with 11 neurons and a linear transfer function (Purelin) at out layer. The Levenberg-Marquardt algorithm (LMA) was applied, giving a minimum mean squared error (MSE) for training and cross validation at the ninth place of decimal. The high correlation coefficient (R2ANN = 0.996) between the model and its closeness to the experimental coefficient (R2Exp = 0.998) showed that the model is able to predict the removal of Cr(VI) from aqueous solutions by iron oxide nanoparticles.

In recent years, as dam safety standards have increased, hydraulic engineers have become more eager to design an economical and safe energy dissipation system at the main flood evacuation course. Ogee spillway and flip bucket are the most used types of spillway and energy dissipation structures. The main aims of the present research were modeling and analyzing hydraulic characteristics of the flow over convergent chute and flip bucket with negative slope of Gelvard Dam, Neka, the north of Iran using Flow-3D software and comparing the results of spillway geometry modification in relation to the initial model. The validation results of numerical model with the experimental data showed that RNG model is the most appropriate turbulence model. Moreover, with respect to the dimensions of computational cells, sensitivity analysis showed that square mesh with dimensions of 0.6 m is appropriate. Considering the results of the numerical modeling, due to increasing the flow velocity more than 20 m/s at the end of chute and maximum pressure of -70000 pa in this area, cavitation threatens the circular arc. Therefore, the slope of the chute and circular arc radius was changed respectively and numerical analysis results were remeasured. The results showed that by reducing the chute slope, the critical points of cavitation decreased from 3 points to 1 point. In addition, it was indicated that changing circular arc radius had no considerable effect on hydraulic characteristics. It just showed that when arc radius increases, jet length increases up to 5 m.

One of the most common types of polymeric waste is beverage bottles. Unfortunately, undertaking basic measures for recycling or reuse of these materials is very limited in Iran and always a huge amount of this waste is released into the environment. The present study was conducted in order to reduce evaporation from water resources of Sarcheshmeh Copper Complex and optimal use of great waste of this polymer. For this purpose, a plan is presented to build a Foamthalate floating cover. This cover was obtained from industrial injection of polystyrene into filled molds with Delester™ bottles. After preparing and constructing coatings, Foamthalate covers were transferred to research ponds in the vicinity of Sarcheshmeh tailing dam and the performance of coatings was evaluated for two months. The obtained results showed performance of Foamthalate coatings in evaporation reduction is more than 90%. Finally, because of the dual-purpose function ofFoamthalate, it can be considered as successful and efficient design to protect the environment and deal with water scarcity challenge.

Floods control, artificial recharge of ground water aquifers, and attempt to optimize the efficiency of water and soil resources are the most important benefits that have been achieved as a result the construction of flood spreading stations in the country. The aim of this research is assessment and determination of economic effects of flood spreading project on water resources and agriculture by monitoring and recording relevant data steadily and continuously. For this purpose, profitability and economic justification of the project were studied using proper criteria of economical evaluation of investment projects. The results showed that water cultivation area of downstream villages of project have been 3.5 folds more compared to the year 2013. Moreover, the added value of the injected flood based on measuring the volume of controlled flood was estimated to be 14.6 Million Rials. The added value of grassland production project became 1354 Million Rials. Whereas, the added values of wood production and agriculture section were estimated to be 13.4 and 657 Million Rials respectively. Economic evaluation indicators of project (NPV, ROR, and B/C) were estimated to be 1399 Million Rials, 0.38, and 2.87 respectively showing economic justification of project.

Investigations have indicated that in-stream structures have better performance rather than alternative structures such as rip-rap revetment and spur-dikes in term of cost, performance, maintenance, and environmental enhancement and help preserve the environment on the banks of meandering rivers. The slotted triangular vanes are among the in-stream structures. This study aimed at investigating the effect of slotted triangular vanes in sedimentary channels bed variation in 90 degrees bend flume (R/B=4, R and B, bend radius and width of the flume, respectively). The experiments were performed by three distances of four, six, and eight times the effective length (Le) in Froude numbers of 0.287, 0.304, and 0.322 under clear water conditions. The bed materials used were sand with an average diameter (d50) of 1.5 mm and a geometric standard deviation ratio (σ) of 1.22. The vanes angle to the upper bank was constant. After conducting analysis, the bed topography and required data were collected. The results showed that by installing the vanes attached to the outer bend flume, local scour occurred at the tips of vanes. By increasing distance between the vanes, the average depth of scour around the tips of vanes increased so that the distance of 4Le presented better performance than the distance 6Le and 8Le in scour protection around vanes. The Scouring bed materials were precipitated on the back of vanes and near outer bank. By increasing distance between the vanes and increasing space between the vanes, scouring bed materials allocated more flume along the length; hence, the maximum mound height decreased.