IRANIAN WATER RESEARCH JOURNAL
Year:2015 | Volume:9 | Issue:2 (17)|Papers Count:21

Area-Reduction method is one of the experimental methods to determine sediment distribution in dam reservoirs. In this method reservoir on the base of geometrically are divided into four types, and sediment distribution in each reservoir type are on the base of the parameter that is given in each reservoir type. Results and researches were shown that in many cases; determining the type of reservoir with the Borland and Miller method didn’t lead to high accuracy. So, determining the optimized coefficient for Area-Reduction method can increase accuracy of sediment distribution prediction in this method. In this study initially a computer model based on Area-Reduction method was provided by using MATLAB software, then optimize model was prepared by using Ant Colony algorithm and this two models were combined. Best coefficients of Area-Reduction method for Karaj Dam were achieved by using this model. Results were shown that there was a significant increase in accuracy of sediment prediction using optimal parameters. Using the optimal parameters, values of objective function reduced up to 68.41%.

Design of a minimum cost canal section involves minimization of the sum of costs per unit length of the canal, subject to uniform flow condition. These costs are included with costs related to covering every meter of channel length, the cost per cubic meter earthworks and costs associated with water loss (including seepage and evaporation losses) as the objective function is considered in this study. Seepage and evaporation are forms of water loss in an irrigation canal, while the seepage loss depends on the canal geometry and evaporation loss is proportional to the area of free surface. In this study, the main constraint equation is Manning’s Formula. In addition, the minimum permissible velocity and Froud’s number are used for optimizing design canal as subsidiary constraints. In this study the Optimization algorithm based on directly search is used and a computer program in MATLAB was developed to solve the above mentioned equations. Feasibility simplex and optimal design to minimize costs of per unit of length of canal is improving with obtained non-dimension carves from results. Studies comparing results with other researchers, can be seen the effect of further constraints and earthworks and cover costs related to the final dimensions of the channel.

Cylindrical weirs are a kind of flow measurement structures in open channels whose crest length is affected by the channel cross section and economical expenses. The current experimental research investigates the effect of side contracting on flow characteristics such as discharge coefficient of cylindrical weirs. The experiments were done on a laboratory flume with dimensions of 7500*300*460 mm, using various diameters of cylindrical weir models in the range of 75£P£160 mm, contraction ratios of 0.2£b/B£1, and various combinations of discharge and flow depth for free flow. The results show that an increase in the ratio of upstream water depth to the weir height (H/P), leads to an increase in the discharge coefficient for all weirs, but when b/B decreases, the gradient of Cd vs. H/P diagram, will decrease too. On the other hand, for any given P and H, the discharge coefficient will increase by increasing the b/B ratio. The contraction coefficient (Cc) for such weirs, determined by using weir theory and experimental data, varies in the range of 0.71 to 0.98 for 1.2£H/P£2.4. These results also show when H/P increases, Cc will increase for all weirs too. Besides, for any given H/P ratio, the flow contraction coefficient over the weir crest will decrease with a decrease in the b/B ratio.

Cylindrical weirs- gates are one of the combined structures types which have advantages such as lower cost, simple design, easy construction and the high discharge coefficient. In current study, the cylindrical weir- gate location in perpendicular orientation to flow direction on discharge coefficient have been investigated experimentally. The experiments were conducted in a flume with the length of 7.5 m and width of 40 cm, using the cylindrical models were made up of plastic pipes with diameters of 50, 75, 110 and 125 mm. Experiments were conducted with different gate opening heights from 0 to 60 mm (reaching to the cylindrical gate by considering the available diameter and discharge). The results show that the maximum and minimum discharge coefficient has been observed respectively, in the cylindrical weir and cylindrical gate. Moreover, by converting the structure from cylindrical weir- gate to cylindrical gate, the curves depicted amount of Cds against the ratio of upstream flow depth to cylinder diameter (yup/D) and the ratio of difference between upstream and downstream flow depth to cylinder diameter ((yup-yd)/D ) have reduced suddenly, which this progress was due to decreasing the amount of back water and remarkable decreasing in upstream depth. Furthermore, increasing in amount of cylindrical structure diameter leads to discharge coefficient amount decrease. The best correlated relations for quantifying the behavior of discharge coefficient Cd, were proposed.

In this study, the combined effects of berth and draft of Pontoon-type floating breakwater on the variation of wave transmission coefficient is examined. To find the width and draft of both floating breakwater on the wave transmission coefficient, three draft 0.8, 1 and 1.2 meters wide and five 2.4, 4.8, 7.2, 9.6 and 12 m were examined. Average for periods of 2, 2.5, 3, 3.5 and 4 seconds, and the range of 0.2 to 1.2 m wave height analysis was performed. According to analysis done by the software ANSYS AQWA and the results showed that the coefficient of wave transmission by increasing the width and draft breakwater float dramatically reduced So that the wave transmission coefficient for breakwater width 2.4 m, draft 0.8, from 0.88 to 0.34 breakwater width is 12 meters and draft 1.2.

The paper describes the evolution of local scour hole downstream of an adverse stilling basin. The research was conducted using a wide range of Froude number, sediment size, tailwater depth, length and slope of stilling basin. The maximum depth of scour and its distance from the stilling basin attained 87.5% in the first 24 hours and 86.3% when the experiment was continued for 54 hours. A power equation was adopted describe the characteristic dimensions of scour hole, time scale as well as geometry of stilling basin and sluice gate. The results showed a certain similarity among the scour profiles developed at different times. However, the shape of the holes was influenced with the change in length and slope of stilling basin. As the slope of stilling basin increased by 15%, the volume of sediment removed from the unit width of the hole, was increased by 30%.

This paper investigates the effects of roughness on flood plain on hydraulic overbank flow in a compound channels with non-prismatic floodplains. Experiments are done using three divergence angles and three-roughness size on the floodplain. The velocity was measured using a three dimensional acoustic Doppler velocimeter and directional current meter in a lattice along the divergence channel in three portions of the flume (entrance, middle and end of the divergence) with different depth ratio. Using the experimental data, the values of the shear stress, depth–averaged velocity, local and zonal roughness coefficients, turbulence parameters and divided discharge between main channel and floodplain were evaluated. The results show that: With increasing the floodplains roughness, in non-prismatic section, the ratio of the velocity at floodplain on main channel decreased about 31% and turbulence flow increased about 25%. Also under these conditions, the shear stress at interface zone was increased from 26% to 48. As well as with increasing depth ratio, the above mentioned values are markedly reduced.

The discharge and suspended sediment concentration are measured only in a few days of the year in most Iranian rivers. Therefore, application of methods which can estimate and forecast the sediment load with the short term or interrupted data is inevitable. The present research was conducted to compare the performance of some data grouping methods for sediment rating curve preparation and another 6 hydrological methods for estimation suspended sediment load in two hydrometric stations located in two different climatic zones of Iran (Ghorbaghestan station located on Gharasoo River and Kordkheil station located on Tajan River). Results showed that in Ghorbaghestan station, the estimated suspended sediment resulted from the sediment rating curve, Smearing and LQMLE methods (in total mode, wet and dry year) were underestimated, while, in the FC1, FC2, FAO, and LQMLE methods (in hydro-climatic and main seasons and composite modes), were overestimated.In Kordkheil station, except FAO method, the estimated suspended sediment resulted from all studied methods were underestimated.

The aim of this research was to apply a two-dimensional hydrodynamic model to predict and investigate governing phenomena on flow, sediment transport and bank erosion in a natural meandering river. The study area is a meander of Karun River with the length of approximately 5 km between Ahvaz and Farsiat hydrometric stations. Bank protection of the considered meander is so important because the Khuzestan Water and Energy company structures and agricultural farms are located in the vicinity. In this study, mesh generation was performed by CCHE-MESH model. The validated CCHE2D model was applied for flow pattern simulation, and bed and bank change prediction in a 20 years period of time. Results showed the meander Thalweg elevation was decreased between 4 to 8 m and 5.7 m in average (in compare with initial bed level) and secondary flow caused a higher decrease in outer bank elevation. Since the Spur dike is an important structure in the river bank protection, 14 number of Spure dikes were designed in the CCHE-2D model for studied meander. After 20 years of simulation, dikes caused to increase the elevation of outer bank between 1 to 9 m and 4.7 m in average (in compare with 20 years of simulation without dikes), But in some sections the Thalweg became approximately 4m deeper.

Side weirs are structures that are installed along a channel and when the height of water is exceeding the crest, extra flow inters to the subsidiary channel. In this research, a solution for differential equation of water surface profile over trapezoidal broad-crested side weir in rectangular channels based on the Haar wavelet transform method is reported. Also, the water surface profiles for different width, height and side slope of the weir were measured and compared to those calculated by using the Haar wavelet method. The Lowest error percentage in calculating y1 (maximum error) was observed in the side slop of side weir of 1.5, width of 8 and height of 10 cm. When height and side slope of the side weir were increased, the accuracy of water surface profile estimations using the Haar wavelet method was decreased. The Haar wavelet method is also compared with Runge-Kutta Method. The correlation coefficient of Haar wavelet method and experimental data was more than 0.979 which was greater than the calculated one for the Runge-Kutta method. This result indicates that the Haar wavelet method can estimate the water depths with higher accuracy than the Runge-Kutta method.

In this study, water resources Decision Support System (DSS), estimates quantitative indicators based on environmental, social and economical criteria under climate scenarios in the Aras river basin. The DSS, analysis the effects of management alternatives on Balance of supply and demand with simulated the water allocation between agricultural, domestic, and industrial demands. The Mike Basin water allocation model linked to Excel spreadsheet to evaluate the performance of 9 proposed indicators of management options and Multi Criteria Decision Making analysis 'TOPSIS' is used to determine the best management options. The results have indicated that the option of 'Reduce losses and Increase efficiency' in the optimistic scenario and the option of 'Reduce losses and Reduce cultivated area' in the pessimistic and business as usual scenarios are in the first ranking. The individually alternatives of 'Don't water transfer to Urmia Lake basin' and 'Decrease cultivated area ' are in the last ranking.

Estimating reference crop evapotranspiration (ETo) is necessary for designing irrigation systems, water resources management, yield production and environmental assessments. Different models and methods have been developed in order to predict ETo using time series, including AR, MA and ARIMA. However, Chaos Theory has not been utilized to estimate the ETo till now. In this study, the performance of the mentioned time series models was evaluated for estimating daily ETo in Torbat-e-Heydarieh synoptic station, Khorasan Razavi, during 1991-2000. Results showed that the ARIMA and Chaos Theory estimate the ETo with the same accuracy, so that the correlation coefficients between observed and estimated values for ARIMA and Chaos Theory were 0.895 and 0.894, and RMSE values were 0.585 and 0.611 mm day-1.

Natural characteristics, especially the climate of each area plays a major role in planning and preparation. Charmahale Bakhtiary is a province that located in the west mountainous area of Iran. Due to topography diversities, this region has a different distribution of climate elements (especially, rainfall and temperature). In order to detect sub-climatic regions, statistical methods such as factor analysis and cluster analysis were used. The climatic parameters were obtained from 6 meteorological stations in the province and to overcome the lack of climate control stations throughout the area Interpolation technique (IDW) was used. Then data matrix with dimensions of 26´46 (variables× stations) was produced and based in factor analysis. The results showed, four major factors which affect the climate of province in order of importance are: the precipitation, the clear sky, the temperature and the humidity. Finally, cluster analysis on the matrix of factor scores recognized the four climate zones.

Agricultural, urban and industrial zones demand for water can be supplied by withdrawing water through reservoirs or conveying channels using vertical intakes. This method usually faces with some problems such as vortex flow formation in inlet. This causes entrainment of air and swirling flow into the intake, which followed by some other difficulties such as reduction of intake capacity and stimulation of vibrations and cavitation inception. In this study, the effect of dimensions, position and type of the horizontal stationary rafts on required submergence to suppress surface vortex (with air core) were examined experimentally. First some tests were carried out to determine discharge-critical submergence relation for a condition in which no anti-vortex device is used. Then, a dimensionless equation was fitted between relative submergence and intake Froude number. After that, the effect of each raft with a specified dimension and position were examined for five different flow rates. The performance of rafts to reduce required submergence is calculated for each setup. Based on the results, the 2d´2d raft at the position of 1d has the best performance of 29.85%. Finally, a regression equation is fitted to predict relative submergence in the presence of anti-vortex rafts, with respect to dimensionless parameters of Froude number, relative plate dimensions and relative installation position.

Growth population and the expansion of activities in different sectors have forced water resources and caused a sharp drop in groundwater levels. Artificial recharge of aquifers by wastewater is one of the most important methods for reusing wastewater. In order to simulate the physical conditions of artificial recharge basin, three cylindrical PVC columns with 30 cm in diameter and 250 cm in height were used. The columns were filled with sandy loam soils and municipal wastewater of Mahdasht in Alborz Province was applied into the columns. Different covering materials such as; geotextile and constructed coarse materials were applied on the top of soil surface to evaluate the performance of those materials in terms of infiltration during permanently pounded condition. Values of EC, pH, suspended solids and phosphate in inflow and outflow of the column were measured. The obtained results indicated a high efficiency for the soil columns covered with geotextile, which reduced suspended solids and phosphorus by 67.7 and 79.9 percent, respectively. The proposed materials can be changed or modified due to their low cost and ease application.

The goal of this paper is, study the effects of creating the surface waves in a uniform flow on bed load transport rate of deposited sediment in a Primal rigid rectangular channel. Experiments were carried out in a rectangular flume of 10m length, 0.2m width and 0.3m height, for two gradations of sediments with median diameters of 0.34 and 0.48 mm and specific weight of 2.67, and for five bed shear stresses (initiation of motion and multiplies of 1.16,1.25,1.39 and 1.43 of it for median diameter of 0.34 mm and initiation of motion and multiplies of 1.15,1.25,1.33 and 1.41 of it for median diameter of 0.48 mm) and two wave heights (1 and 1.6 cm) with four wave speeds. The results showed that creating surface waves increases the bed load transport rate. Furthermore, the bed load transport rate increases with Strouhal number, dimensionless wave height and bed shear stress. It can be concluded that creating artificial waves can increase the bed load transport rate in a rigid rectangular channel up to 280% compared to the no wave conditions.

In this study, the effect of Bend way weir length on bed topography of a sharp 90 degree bend was investigated, experimentally. Tests are conducted at the hydraulic lab of Shahid-Chamran university in a 90 degree sharp bend (R/B=2). Seven Bend way weirs were placed at the outer bank with a height of 5 cm (one-third of flow depth), angel of 30 degrees and three different weir lengths (L/B= 0.15, 0.2 and 0.25), each under four different flow conditions (Froude number ranged from 0.137 to 0.3). At the end of each test, bed topography of bend were taken by a laser bed profiler and plotted by surfer. Comparison of scour and deposition patterns for different weir length shows that weir with the length to width ratio equal 0.2 provides the lowest volume of eroded bed material.

Accurate estimation of suspended sediment in rivers is very important for design and operation of water resources projects. Sediment estimation by conventional methods like rating curves are not able to provide correct results. In this paper, gene expression programming (GEP) model which is an extension to genetic programming (GP) technique, for suspended sediment estimation is applied. The GEP results are compared with those of the adaptive neuro-fuzzy, neural networks and rating curve models. In this regard, the streamflow and suspended sediment data from Vanyar station that located on Aji-chay river in East- Azarbaijan are used. The root mean square errors (RMSE) and determination coefficient (R2) statistics are used for evaluating the accuracy of the models. The results show that the GEP model is the best among other models in estimating suspended sediment. The relative RMSE difference for test period between GEP and ANFIS-Grid Partitioning, ANFIS-Sub Clustering, ANN and rating curves methods was 8, 10, 13 and 21 percent respectively. The R2 values for GEP and ANFIS-Grid Partitioning, ANFIS-Sub Clustering, ANN and rating curves methods was 0.93, 0.84, 0.88, 0.86 and 0.81.

Regional flood frequency analysis is one of the most important methods for estimating flood in poorly gauged or ungauged catchments. In this study, a regional flood frequency analysis has been carried out, using cluster analysis approach in Great Karun watershed. After considering the stations in the area, 44 stations which had good data were selected. The watershed was firstly divided into 3 regions based on the physiographic characteristics and then by using the Hosking & Wallis homogeneity criterion and removing or displacing the stations, the watershed was finally divided into 4 homogeneous regions. In order to find the most suitable regional distributions for homogeneous regions, L-moment ratio diagram and Hosking & Wallis goodness of fit test has been used. The distribution parameters were estimated using the method of probability weighted moments (PWMs). Therefore, by calculating the average discharge, the maximum flood discharge for a given return period can be estimated for ungauged area. By applying this method, the regional flood frequency estimation will be possible for every zone, even ungauged area of the great Karun watershed.

Useful and extensive use of crop models depends on understanding their behavior in response to probable errors in input parameters. The aim of this study was to assess the sensitivity of the simulated sillage-corn yield by the most commonly used crop model, CERES – Maize, to physical soil parameters under two nitrogen fertilizer levels. In this study, by using one year field data of sillage corn in Varamin, the model-output sensitivity to field capacity, saturated water content, curve number, root growth factor, drainage coefficient and albedo was analyzed for two N-fertilizer levels (0 and 150 kg N/ha). To determine the response of model to changes of input parameters, model was run 80 times. After collecting data, the normalized sensitivity of each parameter was calculated using the program written in MATLAB environment. The results showed that the highest model sensitivity in the simulation of the yield in both treatments was shown to field capacity. But the response of the model to changes in input parameters was strongly influenced by the amount of fertilizer. Finally, by using the calculated relative sensitivity values, the relationship between probable error in estimating yield for both fertilizer treatments and error in estimation input data was presented.